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- Parent Category: Products
- Category: Amplifier Measurements

Link: reviewed by Dennis Burger on *SoundStage! Access* on May 1, 2023

**General Information**

All measurements taken using an Audio Precision APx555 B Series analyzer.

The Pro-Ject Audio Systems MaiA DS3 was conditioned for 1 hour at 1/8th full rated power (~10W into 8 ohms) before any measurements were taken. All measurements were taken with both channels driven, using a 120V/20A dedicated circuit, unless otherwise stated.

The MaiA DS3 offers three unbalanced line-level analog inputs (RCA); one unbalanced phono input (RCA) for moving-magnet (MM) or moving-coil (MC) cartridges (selectable with a switch on the rear panel); one coaxial S/PDIF (RCA), two optical S/PDIF (TosLink), and one USB digital input; a Bluetooth input; one line-level subwoofer output (RCA); two line-level pre-outs (RCA, fixed and variable); and a pair of speaker-level outputs. On the front of the unit are a 1/4″ TRS headphone output and a +6dB gain switch for the preamp section. For the purposes of these measurements, the following inputs were evaluated: digital coaxial and the analog line-level and MM/MC unbalanced inputs, with the +6dB gain switch engaged.

Most measurements were made with a 2Vrms line-level analog input, 5mVrms MM input, 0.5mVrms MC input, and 0dBFS digital input. The signal-to-noise ratio (SNR) measurements were made with the same input signal values but with the volume set to achieve the rated output power of 80W (8 ohms). For comparison, on the line-level input, a SNR measurement was also made with the volume at maximum, but with a lower input voltage to achieve the same 80W output.

Based on the inaccuracy and non-repeatable results at various volume levels of the left/right channel matching (see table below), the MaiA DS3 volume control is likely a potentiometer operating in the analog domain. The volume control offers a total range from -66dB to +35.2dB between the line-level analog input and the speaker outputs, with the +6dB switch engaged.

The analyzer’s input bandwidth filter was set to 10Hz–22.4kHz for all measurements, except for frequency-response and FFT charts. Because the MaiA DS3 is a digital amplifier technology that exhibits considerable noise above 20kHz (see FFTs below), the 22.4kHz bandwidth setting was maintained for THD versus frequency sweeps as well. For these sweeps, the highest frequency was 6kHz, to adequately capture the second and third signal harmonics with the restricted-bandwidth setting.

**Volume-control accuracy (measured at speaker outputs): left-right channel tracking**

Volume position | Channel deviation |

min | 0.8dB |

7 o'clock | 0.045dB |

9 o'clock | 0.773dB |

10 o'clock | 0.578dB |

12 o'clock | 0.756dB |

1 o'clock | 0.779dB |

3 o'clock | 0.678dB |

4 o'clock | 0.334dB |

max | 0.039dB |

**Published specifications vs. our primary measurements**

The table below summarizes the measurements published by Pro-Ject for the MaiA DS3 compared directly against our own. The published specifications are sourced from Pro-Ject’s website, either directly or from the manual available for download, or a combination thereof. With the exception of frequency response, where the Audio Precision bandwidth was extended from DC to 250kHz, assume, unless otherwise stated, 10W into 8ohms and a measurement input bandwidth of 10Hz to 22.4kHz, and the worst-case measured result between the left and right channels.

Parameter | Manufacturer | SoundStage! Lab |

Rated output power into 8 ohms (1% THD) | 80W | 80W |

Rated output power into 4 ohms (1% THD) | 140W | 143W |

Frequency response (20Hz - 20kHz, 4 ohms) | <±0.3dB at 20kHz | -1dB at 20kHz |

THD (1kHz, 10W, 8 ohms) | <0.01% | <0.0072% |

SNR (A-weighted, rated output) | 105dB | 107dB |

Input sensitivity (line level, max volume for rated output) | 860mVrms | 883mVrms |

Headphone rated output power into 32 ohms (1% THD) | 430mW | 401mW |

Phono input impedance (MM) | 47k ohms | 52.6k ohms |

Phono input impedance (MC) | 100 ohms | 141 ohms |

Phono gain (MM) | 40dB | 45dB |

Phono gain (MC) | 60dB | 63dB |

Our primary measurements revealed the following using the line-level analog input and digital coaxial input (unless specified, assume a 1kHz sinewave at 2Vrms or 0dBFS, 10W output, 8-ohm loading, 10Hz to 22.4kHz bandwidth):

Parameter | Left channel | Right channel |

Maximum output power into 8 ohms (1% THD+N, unweighted) | 80W | 80W |

Maximum output power into 4 ohms (1% THD+N, unweighted) | 144W | 143W |

Maximum burst output power (IHF, 8 ohms) | 80W | 80W |

Maximum burst output power (IHF, 4 ohms) | 144W | 143W |

Continuous dynamic power test (5 minutes, both channels driven) | passed | passed |

Crosstalk, one channel driven (10kHz) | -61.8dB | -60.6dB |

Damping factor | 85 | 80 |

Clipping no-load output voltage | 26.5Vrms | 26.5Vrms |

DC offset | <10mV | <10mV |

Gain (pre-out) | 3.3/9.4dB | 3.3/9.4dB |

Gain (maximum volume) | 29.2/35.2dB | 29.2/35.3dB |

IMD ratio (CCIF, 18kHz + 19kHz stimulus tones, 1:1) | <-74dB | <-75dB |

IMD ratio (SMPTE, 60Hz + 7kHz stimulus tones, 4:1 ) | <-76dB | <-76dB |

Input impedance (line input, RCA) | 24k ohms | 25k ohms |

Input sensitivity (for rated power, maximum volume) | 883mVrms | 882mVrms |

Noise level (with signal, A-weighted) | <112uVrms | <118uVrms |

Noise level (with signal, 20Hz to 20kHz) | <240uVrms | <240uVrms |

Noise level (no signal, A-weighted) | <103uVrms | <103uVrms |

Noise level (no signal, 20Hz to 20kHz) | <156uVrms | <156uVrms |

Output impedance (pre-out) | 101 ohms | 101 ohms |

Signal-to-noise ratio (80W, A-weighted, 2Vrms in) | 107.7dB | 107.0dB |

Signal-to-noise ratio (80W, 20Hz to 20kHz, 2Vrms in) | 104.2dB | 103.4dB |

Signal-to-noise ratio (80W, A-weighted, max volume) | 108.4dB | 108.4dB |

Dynamic range (80W, A-weighted, digital 24/96) | 107.5dB | 106.8dB |

Dynamic range (80W A-weighted, digital 16/44.1) | 95.5dB | 95.5dB |

THD ratio (unweighted) | <0.0063% | <0.0072% |

THD ratio (unweighted, digital 24/96) | <0.0061% | <0.0077% |

THD ratio (unweighted, digital 16/44.1) | <0.0065% | <0.0078% |

THD+N ratio (A-weighted) | <0.007% | <0.008% |

THD+N ratio (A-weighted, digital 24/96) | <0.007% | <0.0088% |

THD+N ratio (A-weighted, digital 16/44.1) | <0.0076% | <0.009% |

THD+N ratio (unweighted) | <0.007% | <0.008% |

Minimum observed line AC voltage | 124VAC | 124VAC |

For the continuous dynamic power test, the MaiA DS3 was able to sustain 141W into 4 ohms (~2% THD) using an 80Hz tone for 500ms, alternating with a signal at -10dB of the peak (14.1W) for 5s, for 5 continuous minutes without inducing a fault or the initiation of a protective circuit. This test is meant to simulate sporadic dynamic bass peaks in music and movies. During the test, the top of the MaiA DS3 was only slightly warm to the touch.

Our primary measurements revealed the following using the phono-level input, MM configuration (unless specified, assume a 1kHz 5mVrms sinewave input, 10W output, 8-ohm loading, 10Hz to 22.4kHz bandwidth):

Parameter | Left channel | Right channel |

Crosstalk, one channel driven (10kHz) | -58.5dB | -57.7dB |

DC offset | <10mV | <10mV |

Gain (default phono preamplifier) | 45dB | 44.9dB |

IMD ratio (CCIF, 18kHz + 19kHz stimulus tones, 1:1) | <-80dB | <-80dB |

IMD ratio (CCIF, 3kHz + 4kHz stimulus tones, 1:1) | <-59dB | <-59dB |

Input impedance | 51.3k ohms | 52.6k ohms |

Input sensitivity (to max power with max volume) | 2.5mVrms | 2.5mVrms |

Noise level (with signal, A-weighted) | <360uVrms | <330uVrms |

Noise level (with signal, 20Hz to 20kHz) | <800uVrms | <700uVrms |

Noise level (no signal, A-weighted) | <400uVrms | <350uVrms |

Noise level (no signal, 20Hz to 20kHz) | <800uVrms | <700uVrms |

Overload margin (relative 5mVrms input, 1kHz) | 19.1dB | 19.2dB |

Signal-to-noise ratio (80W, A-weighted, 5mVrms in) | 87.3dB | 87.2dB |

Signal-to-noise ratio (80W, 20Hz to 20kHz, 5mVrms in) | 82.0dB | 81.5dB |

Signal-to-noise ratio (80W, A-weighted, max volume) | 81.5dB | 81.0dB |

THD (unweighted) | <0.0068% | <0.0081% |

THD+N (A-weighted) | <0.0085% | <0.0099% |

THD+N (unweighted) | <0.012% | <0.012% |

Our primary measurements revealed the following using the phono-level input, MC configuration (unless specified, assume a 1kHz 0.5mVrms sinewave input, 10W output, 8-ohm loading, 10Hz to 22.4kHz bandwidth):

Parameter | Left channel | Right channel |

Crosstalk, one channel driven (10kHz) | -56.5dB | -48.4dB |

DC offset | <10mV | <10mV |

Gain (default phono preamplifier) | 63.3dB | 63.3dB |

IMD ratio (CCIF, 18kHz + 19kHz stimulus tones, 1:1) | <-72dB | <-72dB |

IMD ratio (CCIF, 3kHz + 4kHz stimulus tones, 1:1) | <-72dB | <-72dB |

Input impedance | 140 ohms | 141 ohms |

Input sensitivity (to max power with max volume) | 0.305mVrms | 0.305mVrms |

Noise level (with signal, A-weighted) | <4mVrms | <3.6mVrms |

Noise level (with signal, 20Hz to 20kHz) | <8mVrms | <7mVrms |

Noise level (no signal, A-weighted) | <4.7mVrms | <4.3mVrms |

Noise level (no signal, 20Hz to 20kHz) | <9mVrms | <8mVrms |

Overload margin (relative 0.5mVrms input, 1kHz) | 20.7dB | 20.8dB |

Signal-to-noise ratio (80, A-weighted, 0.5mVrms in) | 65.8dB | 65.6dB |

Signal-to-noise ratio (80W, 20Hz to 20kHz, 0.5mVrms in) | 60.7dB | 61.2dB |

Signal-to-noise ratio (80W, A-weighted, max volume) | 61.6dB | 61.2dB |

THD (unweighted) | <0.008% | <0.01% |

THD+N (A-weighted) | <0.045% | <0.045% |

THD+N (unweighted) | <0.09% | <0.09% |

Our primary measurements revealed the following using the analog input at the headphone output (unless specified, assume a 1kHz sinewave, 2Vrms output, 300 ohms loading, 10Hz to 22.4kHz bandwidth, and the +6dB gain switch disengaged):

Parameter | Left channel | Right channel |

Maximum output power into 600 ohms (1% THD+N, unweighted) | 94mW | 94mW |

Maximum output power into 300 ohms (1% THD+N, unweighted) | 169mW | 169mW |

Maximum output power into 32 ohms (1% THD+N, unweighted) | 401mW | 405mW |

Gain | 18.6/24.6dB | 18.6/24.7dB |

Output impedance | 34.5 ohms | 34.5 ohms |

Noise level (no signal, A-weighted) | <16uVrms | <16uVrms |

Noise level (no signal, 20Hz to 20kHz) | <23uVrms | <23uVrms |

Signal-to-noise ratio (max output, A-weighted, 2Vrms in) | 112.2dB | 111.5dB |

Signal-to-noise ratio (max output, 20Hz to 20kHz, 2Vrms in) | 109.5dB | 108.8dB |

THD ratio (unweighted) | <0.00077% | <0.0069% |

THD+N ratio (A-weighted) | <0.0011% | <0.0011% |

THD+N ratio (unweighted) | <0.0014% | <0.0014% |

**Frequency response (8-ohm loading, line-level input)**

In our measured frequency response (relative to 1kHz) chart above, the MaiA DS3 is essentially flat within the audioband (-0.09dB at 20Hz, +0.28dB at 20kHz). The rise in relative response at high frequencies is due to the class-D amplifier’s poor damping factor (*i.e.*, high output impedance) at high frequencies. When the frequency response into 4 ohms is plotted (see RMS level v frequency v load graphs below), we find a dip in response at high frequencies. In the graph above and most of the graphs below, only a single trace may be visible. This is because the left channel (blue or purple trace) is performing identically to the right channel (red or green trace), and so they perfectly overlap, indicating that the two channels are ideally matched. Because the MaiA DS3 exhibited poor channel tracking, we’ve also plotted . . .

. . . RMS level vs frequency, to show the channel-to-channel deviations. In the chart above, we can see that the right channel is roughly 0.8dB lower in output than the left channel. This is due to the deviations inherent to the potentiometer used to control the volume.

**Phase response (line-level input)**

Above is the phase response plot from 20Hz to 20kHz for the line-level input, measured across the speaker outputs at 10W into 8 ohms. The MaiA DS3 does not invert polarity. Here we find a worst case of about +30 degrees at 20Hz and 20kHz.

**Frequency response (line-level analog input, subwoofer line-level output)**

In our measured frequency response of the line-level subwoofer output shown above, the MaiA DS3 is at 0dB at 20Hz and -0.5dB at 20kHz. As a result, it is clear that the sub-out does not offer any built-in low-pass filtering.

**Frequency response vs. input type (8-ohm loading, left channel only)**

The chart above shows the MaiA DS3’s frequency response (relative to 1kHz) as a function of input type measured across the speaker outputs at 10W into 8 ohms. The blue trace is for a 16-bit/44.1kHz dithered digital input signal from 10Hz to 22kHz using the coaxial digital input, and the purple trace is for a 24/96 dithered digital input signal from 10Hz to 48kHz, while the pink trace is for a 24/192 dithered digital input signal from 10Hz to 96kHz. The green trace is the same analog input frequency response seen above. The 16/44.1 data exhibits brickwall-type filtering, with a -3dB at 21.2kHz. The 24/96 and 24/192 kHz data were nearly identical, yielding -3dB points at 45.3kHz and 46.5kHz respectively. The analog input data yields a -3dB point at 58kHz.

**Frequency response (8-ohm loading, MM phono input)**

The chart above shows the frequency response (relative to 1kHz) for the MM phono input. We see maximum deviations within about ±0.25dB from 20Hz to 20kHz for the left channel, and about ±0.5dB for the right channel. What is shown is the deviation from the RIAA curve, where the input signal sweep is EQ’d with an inverted RIAA curve supplied by Audio Precision (*i.e.*, zero deviation would yield a flat line at 0dB).

**Phase response (MM input)**

Above is the phase response plot from 20Hz to 20kHz for the MM phono input, measured across the speaker outputs at 10W into 8 ohms. The MaiA DS3 does not invert polarity. For the phono input, since the RIAA equalization curve must be implemented, which ranges from +19.9dB (20Hz) to -32.6dB (90kHz), phase shift at the output is inevitable. Here we find a worst case of about -60 degrees at 200Hz and 5kHz.

**Frequency response (8-ohm loading, MC phono input)**

The chart above shows the frequency response (relative to 1kHz) for the MC phono input. What is shown is the deviation from the RIAA curve, where the input signal sweep is EQ’d with an inverted RIAA curve supplied by Audio Precision (i.e., zero deviation would yield a flat line at 0dB). We see maximum deviations within about ±0.5dB from 20Hz to 20kHz for both channels, although the left channel is much flatter than the right channel between 100Hz and 10kHz.

**Phase response (MC input)**

Above is the phase response plot from 20Hz to 20kHz for the MC phono input, measured across the speaker outputs at 10W into 8 ohms. The MaiA DS3 does not invert polarity. The response is essentially identical to the phase response for the MM input above.

**Digital linearity (16/44.1 and 24/96 data)**

The chart above shows the results of a linearity test for the coaxial digital input for both 16/44.1 (blue/red) and 24/96 (purple/green) input data, measured at the fixed line-level pre-outs of the MaiA DS3 for a 1.36Vrms (at 0dBFS) output signal. The digital input is swept with a dithered 1kHz input signal from -120dBFS to 0dBFS, and the output is analyzed by the APx555. The ideal response would be a straight flat line at 0dB. Both data were essentially perfect as of -100dBFS down to 0dBFS. At -120dBFS, the 16/44.1 data were about +2dB (left/right channels) above reference, while the 24/96 data were still at the reference 0dB level. This is a good linearity test result.

**Impulse response (24/44.1 data)**

The graph above shows the impulse response for a looped 24/44.1 test file that moves from digital silence to full 0dBFS (all “1”s) for one sample period then back to digital silence, measured at the fixed line-level pre-outs of MaiA DS3. We can see that the MaiA DS3 utilizes a typical symmetrical sinc function reconstruction filter.

**J-Test (coaxial)**

The chart above shows the results of the J-Test test for the coaxial digital input measured at the line level pre-outs of the MaiA DS3. J-Test was developed by Julian Dunn in the 1990s. It is a test signal—specifically, a -3dBFS undithered 12kHz squarewave sampled (in this case) at 48kHz (24 bits). Since even the first odd harmonic (*i.e.*, 36kHz) of the 12kHz squarewave is removed by the bandwidth limitation of the sampling rate, we are left with a 12kHz sinewave (the main peak). In addition, an undithered 250Hz squarewave at -144dBFS is mixed with the signal. This test file causes the 22 least significant bits to constantly toggle, which produces strong jitter spectral components at the 250Hz rate and its odd harmonics. The test file shows how susceptible the DAC and delivery interface are to jitter, which would manifest as peaks above the noise floor at 500Hz intervals (*e.g.*, 250Hz, 750Hz, 1250Hz, etc.). Note that the alternating peaks are in the test file itself, but at levels of -144dBrA and below. The test file can also be used in conjunction with artificially injected sinewave jitter by the Audio Precision, to show how well the DAC rejects jitter.

The coaxial input exhibits low-level peaks in the audioband, as high as -130dBrA. This is an average J-Test result, indicating that the MaiA DS3 DAC may be susceptible to jitter.

**J-Test (optical)**

The chart above shows the results of the J-Test test for the optical digital input measured at the fixed line-level pre-outs of the MaiA DS3. It is essentially the same result as with the coax input shown above.

**J-Test with 100ns of injected jitter (coaxial)**

Both the coaxial and optical inputs were also tested for jitter immunity by injecting 100ns of artificial sinewave jitter at 2kHz, which would manifest as sidebands at 10kHz and 14kHz without any jitter rejection. Jitter immunity proved poor at the 100ns level, with visible sidebands at -100dBrA. The optical input jitter result was very similar to the coaxial input result.

**J-Test with 500ns of injected jitter (coaxial)**

Both the coaxial and optical inputs were also tested for jitter immunity by injecting 500ns of artificial sinewave jitter at 2kHz, which would manifest as sidebands at 10kHz and 14kHz without any jitter rejection. Jitter immunity proved poor, with visible sidebands at -85dBrA. The MaiA DS3DAC did lose sync with the signal when jitter was increased beyond 500ns. The optical input jitter result was very similar to the coaxial input result.

**Wideband FFT spectrum of white noise and 19.1kHz sinewave tone (coaxial input)**

The plot above shows a fast Fourier transform (FFT) of the MaiA DS3’s fixed line-level pre-outs with white noise at -4 dBFS (blue/red) and a 19.1 kHz sinewave (purple/green) at 0dBFS fed to the coaxial digital input, sampled at 16/44.1. The sharp roll-off above 20kHz in the white-noise spectrum shows the implementation of a brick-wall type reconstruction filter. There are no aliased image peaks in the audioband above the noise floor at -135dBrA. The main 25kHz alias peak is highly suppressed at -105dBrA. The second, third, and fourth distortion harmonics (38.2, 57.3, 76.4kHz) of the 19.1kHz tone are between -90dBrA and -100dBrA.

**RMS level vs. frequency vs. load impedance (1W, left channel only)**

The chart above shows RMS level (relative to 0dBrA, which is 1W into 8 ohms, or 2.83Vrms) as a function of frequency, for the analog line-level input swept from 5Hz to 100kHz. The blue plot is into an 8-ohm load, the purple is into a 4-ohm load, the pink plot is an actual speaker (Focal Chora 806, measurements can be found here), and the cyan plot is no load connected. The chart below . . .

. . . is the same but zoomed in to highlight differences. Here we can see a significant maximum deviation at 20kHz of about 2.3dB from 4 ohms to no load, which is an indication of a very low damping factor at high frequencies, or high output impedance. The deviation in RMS level below 2kHz from no load to 4 ohms is much less, at about 0.2dB. The variation in RMS level when a real speaker was used is also significant, deviating by about 0.3-0.4dB, with the lowest response at 200Hz, and the highest at 5kHz.

**THD ratio (unweighted) vs. frequency vs. output power**

The chart above shows THD ratios at the output into 8 ohms as a function of frequency for a sinewave stimulus at the analog line-level input. The blue and red plots are for left and right channels at 1W output into 8 ohms, purple/green at 10W, and pink/orange at 55W. The power was varied using the volume control. At 1W, THD ratios ranged from 0.007% at 20Hz, down to 0.002% at 6kHz. At 10W, THD ratios ranged from 0.02% at 20Hz, down to 0.005% at 2-3kHz. The 55W THD values are higher and range from 0.05% at 20Hz, down to 0.015% at 2kHz, then up to 0.03% at 6kHz. These data corroborate Pro-Ject’s claim of less than 0.01% THD at 10W at 1kHz.

**THD ratio (unweighted) vs. frequency at 10W (MM/MC input)**

The chart above shows THD ratios as a function of frequency plots for the MM and MC phono input configurations measured across an 8-ohm load at 10W. The input sweep is EQ’d with an inverted RIAA curve. The THD values for the MM configuration vary from around 0.02% (20Hz) down to just beow 0.01% at 1-2kHz, the back up to 0.02% at 6kHz. The THD values for the MC configuration vary from around 0.08% (20Hz) down to as low as 0.003% (left channel) at 3kHz, then up to 0.01% at 6kHz.

**THD ratio (unweighted) vs. output power at 1kHz into 4 and 8 ohms**

The chart above shows THD ratios measured at the output of the MaiA DS3 as a function of output power for the analog line-level input, for an 8-ohm load (blue/red for left/right channels) and a 4-ohm load (purple/green for left/right channels). Both data sets track fairly closely, with the 8-ohm data outperforming the 4-ohm data by about 5dB. The 8-ohm data ranges from around 0.002% at 1W and below, up to 0.015% at the “knee” around 70W, then up to the 1% THD mark at the rated 80W. With a 4-ohm load, the “knee” occurs at about 120W, and the 1% THD value was reached at 144W.

**THD+N ratio (unweighted) vs. output power at 1kHz into 4 and 8 ohms**

The chart above shows THD+N ratios measured at the output of the MaiA DS3 as a function of output power for the analog line-level input, for an 8-ohm load (blue/red for left/right channels) and a 4-ohm load (purple/green for left/right channels). Overall, THD+N values for both loads were similar, ranging from 0.02%, down to just below 0.01%, with the 8-ohm data outperforming the 4-ohm data by about 2-5dB.

**THD ratio (unweighted) vs. frequency at 8, 4, and 2 ohms (left channel only)**

The chart above shows THD ratios measured at the output of the MaiA DS3 as a function of frequency into three different loads (8/4/2 ohms) for a constant input voltage that yielded 10W at the output into 8 ohms (and roughly 20W into 4 ohms, and 40W into 2 ohms) for the analog line-level input. The 8-ohm load is the blue trace, the 4-ohm load the purple trace, and the 2-ohm load the pink trace. We find the 8-ohm trace ranging from 0.01% at 20Hz down to 0.003% at 2kHz, and outperforming the 4-ohm trace by about 5dB (except at 6kHz, where both data sets yielded THD ratios of 0.01%). THD values with a 2-ohm load were much higher, ranging from 0.05% at 20Hz, down to 0.03% at 400Hz, then up to 0.1% at 6kHz. Nonetheless, these data show that the MaiA DS3 is stable into 2-ohm loads.

**THD ratio (unweighted) vs. frequency into 8 ohms and real speakers (left channel only)**

The chart above shows THD ratios measured at the output of the MaiA DS3 as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). At lower frequencies, the two-way speaker yielded the highest THD ratios, as high as 0.15% at 20Hz, but as low as 0.001% at 3-4kHz. The three-way speaker ranged from a high of 0.015% at 20Hz, down to 0.0025% at 2kHz, and up to 0.015% at 6kHz. Generally, THD ratios were higher with real speakers compared to the 8-ohm dummy resistive load.

**IMD ratio (CCIF) vs. frequency into 8 ohms and real speakers (left channel only)**

The chart above shows intermodulation distortion (IMD) ratios measured at the output of the MaiA DS3 as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. Here the CCIF IMD method was used, where the primary frequency is swept from 20kHz (F1) down to 2.5kHz, and the secondary frequency (F2) is always 1kHz lower than the primary, with a 1:1 ratio. The CCIF IMD analysis results are the sum of the second (F1-F2 or 1kHz) and third modulation products (F1+1kHz, F2-1kHz). The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). The results for the dummy load were fairly consistent, hovering between 0.003% and 0.005% from 2.5kHz to 20kHz. We find that the two-way speaker yielded IMD ratios 15dB higher than the dummy load above 10kHz, reaching 0.04% at 20kHz, compared to 0.005% for the dummy load. The three-way speaker yielded IMD ratios roughly 15dB higher than the dummy load across the swepted frequencies.

**IMD ratio (SMPTE) vs. frequency into 8 ohms and real speakers (left channel only)**

The chart above shows IMD ratios measured at the output of the MaiA DS3 as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. Here, the SMPTE IMD method was used, where the primary frequency (F1) is swept from 250Hz down to 40Hz, and the secondary frequency (F2) is held at 7kHz with a 4:1 ratio. The SMPTE IMD analysis results consider the second (F2 ± F1) through the fifth (F2 ± 4xF1) modulation products. The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). All three results are similar, with the two-way speaker and dummy load consistently yielding 0.01% IMD, and the three-way speaker reaching 0.02% from 100Hz to 250Hz.

**FFT spectrum – 1kHz (line-level input)**

Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the analog line-level input. We see that the signal’s second harmonic (2kHz) dominates at around -85dBrA, or 0.006%. The subsequent signal harmonics are around or below -100dBrA, or 0.001%. There are clearly visible power-supply-related noise peaks at even harmonics (120Hz, 240Hz, 360Hz, etc.) on the left side of the main 1kHz peak, at -95dBrA, or 0.002%, down to -120dBrA, or 0.0001%. There is also a rise in the noise above 20kHz, characteristic of digital amplifiers.

**FFT spectrum – 1kHz (digital input, 16/44.1 data at 0dBFS)**

Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the coaxial digital input, sampled at 16/44.1. The signal and noise-related harmonics are very similar to the FFT above for the analog input.

**FFT spectrum – 1kHz (digital input, 24/96 data at 0dBFS)**

Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the coaxial digital input, sampled at 24/96. The signal- and noise-related harmonics are very similar to the FFT above for the analog input.

**FFT spectrum – 1kHz (digital input, 16/44.1 data at -90dBFS)**

Shown above is the FFT for a 1kHz -90dBFS dithered 16/44.1 input sinewave stimulus at the coaxial digital input, measured at the output across an 8-ohm load. We see the 1kHz primary signal peak, at the correct amplitude, and signal harmonics from the right channel at -90dBrA, or 0.003%, and below. The noise floor is also elevated, as high as -110dBrA.

**FFT spectrum – 1kHz (digital input, 24/96 data at -90dBFS)**

Shown above is the FFT for a 1kHz -90dBFS dithered 24/96 input sinewave stimulus at the coaxial digital input, measured at the output across an 8-ohm load. We see the 1kHz primary signal peak, at the correct amplitude, and signal harmonics from the right channel at -90dBrA, or 0.003%, and below. The noise floor is also elevated, as high as -110dBrA.

**FFT spectrum – 1kHz (MM phono input)**

Shown above is the FFT for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the MM phono input. We see that the signal’s second harmonic (2kHz) dominates at around -85dBrA, or 0.006%. The subsequent signal harmonics are around or below -100dBrA, or 0.001%. There are clearly visible power-supply-related noise peaks at even and odd harmonics (60Hz, 120Hz, 180Hz, 240Hz, etc.) on the left side of the main 1kHz peak, at -90dBrA, or 0.003%, down to -110dBrA, or 0.0003%.

**FFT spectrum – 1kHz (MC phono input)**

Shown above is the FFT for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the MC phono input. We see that the signal’s second harmonic (2kHz) dominates at around -90/85dBrA (left/right channels), or 0.003/0.006%. Most of the subsequent signal harmonics are buried beneath the noise-floor, which ranges from -100dBrA to -120dBrA from 2kHz to 20kHz. There are three clearly visible power-supply related noise peaks at 60Hz, 120Hz and 180Hz, on the left side of the main 1kHz peak, at -70dBrA, or 0.03%, and -85dBrA, or 0.006%.

**FFT spectrum – 50Hz (line-level input)**

Shown above is the FFT for a 50Hz input sinewave stimulus measured at the output across an 8-ohm load at 10W for the analog line-level input. The X axis is zoomed in from 40Hz to 1kHz, so that peaks from noise artifacts can be directly compared against peaks from the harmonics of the signal. We see that the signal’s second harmonic (100Hz) dominates at around -75dBrA, or 0.02%. The subsequent signal harmonics are around or below -100dBrA, or 0.001%. There are clearly visible power-supply-related noise peaks at even harmonics (120Hz, 240Hz, 360Hz, etc.) at -95dBrA, or 0.002%, down to -120dBrA, or 0.0001%.

**FFT spectrum – 50Hz (MM phono input)**

Shown above is the FFT for a 50Hz input sinewave stimulus measured at the output across an 8-ohm load at 10W for the MM phono input. The X axis is zoomed in from 40 Hz to 1kHz, so that peaks from noise artifacts can be directly compared against peaks from the harmonics of the signal. We see that the signal’s second harmonic (100Hz) dominates at around -75dBrA, or 0.02%. The subsequent signal harmonics are around or below -100dBrA, or 0.001%. There are clearly visible power-supply-related noise peaks at even and odd harmonics (60Hz, 120Hz, 180Hz, 240Hz, etc.) at -90dBrA, or 0.003%, down to -110dBrA, or 0.0003%.

**FFT spectrum – 50Hz (MC phono input)**

Shown above is the FFT for a 50Hz input sinewave stimulus measured at the output across an 8-ohm load at 10W for the MC phono input. The X axis is zoomed in from 40Hz to 1kHz, so that peaks from noise artifacts can be directly compared against peaks from the harmonics of the signal. We see that the signal’s second harmonic (100Hz) dominates at around -80dBrA, or 0.01%. Most of the subsequent signal harmonics are buried beneath the noise-floor, which ranges from -90dBrA to -110dBrA from 50Hz to 1kHz. There are three clearly visible power-supply-related noise peaks at 60Hz, 120Hz, and 180Hz at -70dBrA, or 0.03%, and -85dBrA, or 0.006%.

**Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, line-level input)**

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the output across an 8-ohm load at 10W for the analog line-level input. The input RMS values are set at -6.02dBrA so that, if summed for a mean frequency of 18.5kHz, would yield 10W (0dBrA) into 8 ohms at the output. We find that the second-order modulation product (*i.e.*, the difference signal of 1kHz) is at -90dBrA or 0.003%. The third-order modulation products, at 17kHz and 20kHz, are at around the same level.

**Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, coaxial digital input, 16/44.1)**

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the output across an 8-ohm load at 10W for the digital coaxial input at 16/44.1. We find that the second-order modulation product (*i.e.*, the difference signal of 1kHz) is at -90dBrA, or 0.003%. The third-order modulation products, at 17kHz and 20kHz, are at around the same level.

**Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, coaxial digital input, 24/96)**

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the output across an 8-ohm load at 10W for the digital coaxial input at 24/96. We find that the second-order modulation product (*i.e.*, the difference signal of 1kHz) is at -90dBrA, or 0.003%. The third-order modulation products, at 17kHz and 20kHz, are at around the same level.

**Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, MM phono input)**

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the output across an 8-ohm load at 10W for the MM phono input. We find that the second-order modulation product (*i.e.*, the difference signal of 1kHz) is at -70dBrA, or 0.03%. The third-order modulation products, at 17kHz and 20kHz, are at around the same level.

**Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, MC phono input)**

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the output across an 8-ohm load at 10W for the MC phono input. We find that the second-order modulation product (*i.e.*, the difference signal of 1kHz) is at -90dBrA, or 0.003%. The third-order modulation products, at 17kHz and 20kHz, are at around the same level.

**Square-wave response (10kHz)**

Above is the 10kHz squarewave response using the analog line-level input, at roughly 10W into 8 ohms. Due to limitations inherent to the Audio Precision APx555 B Series analyzer, this graph should not be used to infer or extrapolate the MaiA DS3’s slew-rate performance. Rather, it should be seen as a qualitative representation of the MaiA DS3’s average bandwidth. An ideal squarewave can be represented as the sum of a sinewave and an infinite series of its odd-order harmonics (*e.g.*, 10kHz + 30kHz + 50kHz + 70kHz . . .). A limited bandwidth will show only the sum of the lower-order harmonics, which may result in noticeable undershoot and/or overshoot, and softening of the edges. Here we can see the 600kHz switching oscillator frequency used in the digital amplifier section visibly modulating the waveform.

**Square-wave response (10kHz, restricted 250kHz bandwidth)**

Above is the 10kHz squarewave response using the analog line-level input, at roughly 10W into 8 ohms, this time with a 250kHz input bandwidth on the analyzer to filter out the 600kHz switching frequency. We see more evidence here, in the overshoot and soft corners of the squarewave, of the MaiA DS3’s average bandwidth.

**FFT spectrum (1MHz bandwidth)**

The MaiA DS3’s class-D amplifier relies on a switching oscillator to convert the input signal to a pulse-width-modulated (PWM) squarewave (on/off) signal before sending the signal through a low-pass filter to generate an output signal. The MaiA DS3 oscillator switches at a rate of about 600kHz, and this graph plots a wide bandwidth FFT spectrum of the amplifier’s output at 10W into 8 ohms as it’s fed a 1kHz sinewave. We can see that the 600kHz peak is quite evident, and at -40dBrA. There is also a peak at 1.2MHz (the second harmonic of the 600kHz peak), at -80dBrA. Those peaks—the fundamental and its harmonic—are direct results of the switching oscillators in the MaiA DS3’s amp modules. The noise around those very-high-frequency signals are in the signal, but all that noise is far above the audioband—and therefore inaudible—and so high in frequency that any loudspeaker the amplifier is driving should filter it all out anyway.

**Damping factor vs. frequency (20Hz to 20kHz)**

The final graph above is the damping factor as a function of frequency. Both channels show a relatively constant damping factor from 20Hz to 2kHz, at around 86/80 (left/right). Above 2kHz, we see a steep decline in damping factor, as low as 10 at 20kHz, which is typical of this type of digital-amplifier technology.

*Diego Estan*

Electronics Measurement Specialist

- Details
- Parent Category: Products
- Category: Amplifier Measurements

Link: reviewed by Dennis Burger on *SoundStage! Access* on March 1, 2023

**General Information**

All measurements taken using an Audio Precision APx555 B Series analyzer.

Note: The latest firmware (released February 25, 2023) was applied to the C 3050 LE by NAD because an issue was discovered with the original firmware. The C 3050 LE preamp section is intended to provide a maximum of 12dB of gain; however, with the original firmware, a maximum of 0dB of gain (unity gain) was measured. Dennis Burger’s review sample would have had this issue, and explains his experience of having to turn the volume up higher than normal.

The C 3050 LE was conditioned for 1 hour at 1/8th full rated power (~12W into 8 ohms) before any measurements were taken. All measurements were taken with both channels driven, using a 120V/20A dedicated circuit, unless otherwise stated.

The C 3050 LE offers one unbalanced line-level analog input (RCA), one unbalanced moving-magnet (MM) phono input (RCA), one coaxial (RCA) and one optical (TosLink) S/PDIF digital input, Bluetooth connectivity, HDMI and Ethernet connections for streaming (using the included MDC BluOS module), one line-level subwoofer output (RCA), one set of line-level pre-out and main-in (both RCA) inputs and outputs, and two pairs of speaker-level outputs. On the front of the unit is a 1/4″ TRS headphone output. For the purposes of these measurements, the following inputs were evaluated: digital coaxial, and the analog line-level and MM unbalanced inputs.

Most measurements were made with a 2Vrms line-level analog input, 5mVrms MM input, and 0dBFS digital input. The C 3050 LE digitizes all incoming analog signals (line-level and phono) using a 48kHz sample rate. The signal-to-noise ratio (SNR) measurements were made with the same input signal values but with the volume set to achieve the rated output power of 100W (8 ohms). For comparison, on the line-level input, a SNR measurement was also made with the volume at maximum, but with a lower input voltage to achieve the same 100W output.

Based on the accuracy and reasonably repeatable results at various volume levels of the left/right channel matching (see table below), the C 3050 LE volume control is likely operating fully in the digital domain. The volume control offers a total range from -51dB to + 41dB between the line-level analog input and the speaker outputs, in 0.5dB increments.

The analyzer’s input bandwidth filter was set to 10Hz–22.4kHz for all measurements, except for frequency response and FFTs. Because the C 3050 LE is a digital amplifier technology that exhibits considerable noise above 20kHz (see FFTs below), the 22.4kHz bandwidth setting was maintained for THD versus frequency sweeps as well. For these sweeps, the highest frequency was 6kHz, to adequately capture the second and third signal harmonics with the restricted-bandwidth setting.

**Volume-control accuracy (measured at speaker outputs): left-right channel tracking**

Volume position | Channel deviation |

min | 0.150dB |

10% | 0.135dB |

20% | 0.116dB |

30% | 0.113dB |

40% | 0.123dB |

50% | 0.180dB |

70% | 0.168dB |

80% | 0.148dB |

max | 0.125dB |

**Published specifications vs. our primary measurements**

The table below summarizes the measurements published by NAD for the C 3050 LE compared directly against our own. The published specifications are sourced from NAD’s website, either directly or from the manual available for download, or a combination thereof. With the exception of frequency response, where the Audio Precision bandwidth was extended from DC to 250kHz, assume, unless otherwise stated, 10W into 8ohms and a measurement input bandwidth of 10Hz to 22.4kHz, and the worst-case measured result between the left and right channels.

Parameter | Manufacturer | SoundStage! Lab |

Rated output power into 8 ohms (0.03% THD, 20Hz to 6.5kHz) | 100W | 92W (at 0.03% THD) |

Rated output power into 4 ohms (0.03% THD, 20Hz to 6.5kHz) | 100W | 158W (at 0.03% THD) |

THD (20Hz-6.5kHz, 0.25 to 100W, 8 and 4 ohms) | <0.03% | <0.05% |

SNR (A-weighted, ref. 1W out in 8 ohms, 500mV input) | >95dB | 88dB |

Clipping power (1kHz, 8 ohms, 0.1%THD) | >115W | 108W |

IHF dynamic power (8 ohms) | 180W | 136.2W |

IHF dynamic power (4 ohms) | 250W | 246.8W |

Frequency response (20Hz-20kHz) | ±0.3dB | ±0.15dB |

Channel separation (1kHz, 1W) | >75dB | 91dB |

Channel separation (10kHz, 1W) | >70dB | 82dB |

Input sensitivity (analog) | 540mVrms | 250mVrms |

Input sensitivity (digital) | -6dBFS | -18.7dBFS |

Preamp out THD (20Hz-20kHz, 2Vrms) | <0.005% | <0.005% |

Preamp out SNR (A-weighted, ref. 500mV out, unity gain) | >95dB | 91dB |

Preamp out channel separation (1kHz) | >100dB | 108dB |

Preamp out channel separation (10kHz) | >90dB | 89dB |

Input impedance | 28k ohms | 31.8k ohms |

Maximum input signal (0.1% THD) | >4.5Vrms | 2.15Vrms |

Preamp output impedance | 440 ohms | 439 ohms |

Preamp input sensitivity (ref 0.5Vrms out, volume maximum) | 270mVrms | 220mVrms |

Maximum output signal (0.1% THD) | >2Vrms | 2.6Vrms |

Preamp out, phono in THD (20Hz-20kHz, 2Vrms) | <0.03% | <0.01% |

Preamp out, phono in SNR (A-weighted, ref. 500mV out) | >79dB | 79dB |

Input impedance (phono) | 46k ohms | 53.9k ohms |

Preamp phono input sensitivity (ref 0.5Vrms out, volume maximum) | 5.5mVrms | 5.1mVrms |

Preamp out, phono in frequency response (20Hz-20kHz) | ±0.3dB | ±0.15dB |

Maximum phono input signal (0.1% THD, 1kHz) | >80mVrms | 45mVrms |

Headphone out THD (20Hz-20kHz, 1Vrms, 300 ohm load) | <0.005% | <0.2% |

Headphone out SNR (A-weighted, ref. 2V out, unity gain, 32 ohm load) | >96dB | 103dB |

Headphone out channel separation (1kHz, 1V out, 300 ohm load) | >60dB | 69dB |

Our primary measurements revealed the following using the line-level analog input and digital coaxial input (unless specified, assume a 1kHz sinewave at 2Vrms or 0dBFS, 10W output, 8-ohm loading, 10Hz to 22.4kHz bandwidth):

Parameter | Left channel | Right channel |

Maximum output power into 8 ohms (1% THD+N, unweighted) | 111W | 109W |

Maximum output power into 4 ohms (1% THD+N, unweighted) | 167W | 164W |

Maximum burst output power (IHF, 8 ohms) | 136.2W | 137.9W |

Maximum burst output power (IHF, 4 ohms) | 246.8W | 246.8W |

Continuous dynamic power test (5 minutes, both channels driven) | passed | passed |

Crosstalk, one channel driven (10kHz) | -90.2dB | -82.7dB |

Damping factor | 201 | 242 |

Clipping no-load output voltage | 34Vrms | 34Vrms |

DC offset | <-0.1mV | <17mV |

Gain (pre-out) | 12.05dB | 11.92dB |

Gain (maximum volume) | 41.09dB | 40.96dB |

IMD ratio (CCIF, 18kHz + 19kHz stimulus tones, 1:1) | <-69dB | <-69dB |

IMD ratio (SMPTE, 60Hz + 7kHz stimulus tones, 4:1 ) | <-74dB | <-75dB |

Input impedance (line input, RCA) | 31.8k ohms | 31.3k ohms |

Input sensitivity (for rated power, maximum volume) | 250mVrms | 253mVrms |

Noise level (with signal, A-weighted) | <130uVrms | <132uVrms |

Noise level (with signal, 20Hz to 20kHz) | <166uVrms | <167uVrms |

Noise level (no signal, A-weighted) | <102uVrms | <97uVrms |

Noise level (no signal, 20Hz to 20kHz) | <130uVrms | <124uVrms |

Output impedance (pre-out) | 440 ohms | 439 ohms |

Signal-to-noise ratio (100W, A-weighted, 2Vrms in) | 102.3dB | 103.0dB |

Signal-to-noise ratio (100W, 20Hz to 20kHz, 2Vrms in) | 100.2dB | 100.8dB |

Signal-to-noise ratio (100W, A-weighted, max volume) | 84.7dB | 85.7dB |

Dynamic range (100W, A-weighted, digital 24/96) | 109.1dB | 109.1dB |

Dynamic range (100W A-weighted, digital 16/44.1) | 95.9dB | 95.9dB |

THD ratio (unweighted) | <0.0055% | <0.0050% |

THD ratio (unweighted, digital 24/96) | <0.0049% | <0.0051% |

THD ratio (unweighted, digital 16/44.1) | <0.0049% | <0.0051% |

THD+N ratio (A-weighted) | <0.0065% | <0.0059% |

THD+N ratio (A-weighted, digital 24/96) | <0.0057% | <0.0059% |

THD+N ratio (A-weighted, digital 16/44.1) | <0.0059% | <0.0062% |

THD+N ratio (unweighted) | <0.0058% | <0.0054% |

Minimum observed line AC voltage | 125VAC | 25VAC |

For the continuous dynamic power test, the C 3050 LE was able to sustain 171W into 4 ohms (~3% THD) using an 80Hz tone for 500ms, alternating with a signal at -10dB of the peak (17.1W) for 5 seconds, for 5 continuous minutes without inducing a fault or the initiation of a protective circuit. This test is meant to simulate sporadic dynamic bass peaks in music and movies. During the test, the top of the C 3050 LE was only slightly warm to the touch.

Our primary measurements revealed the following using the phono-level input, MM configuration (unless specified, assume a 1kHz 5mVrms sinewave input, 10W output, 8-ohm loading, 10Hz to 22.4kHz bandwidth):

Parameter | Left channel | Right channel |

Crosstalk, one channel driven (10kHz) | -84.3dB | -72.2dB |

DC offset | <-0.8mV | <16.8V |

Gain (default phono preamplifier) | 33.8dB | 33.8dB |

IMD ratio (CCIF, 18kHz + 19kHz stimulus tones, 1:1) | <-78dB | <-77dB |

IMD ratio (CCIF, 3kHz + 4kHz stimulus tones, 1:1) | <-82dB | <-82dB |

Input impedance | 52.3k ohms | 53.9k ohms |

Input sensitivity (to max power with max volume) | 5.1mVrms | 5.2mVrms |

Noise level (with signal, A-weighted) | <980uVrms | <950uVrms |

Noise level (with signal, 20Hz to 20kHz) | <3000uVrms | <3000uVrms |

Noise level (no signal, A-weighted) | <1100Vrms | <1100uVrms |

Noise level (no signal, 20Hz to 20kHz) | <3000uVrms | <3000uVrms |

Overload margin (relative 5mVrms input, 1kHz) | 19.1dB | 19.1dB |

Signal-to-noise ratio (100W, A-weighted, 5.2mVrms in) | 79.2dB | 79.3dB |

Signal-to-noise ratio (100W, 20Hz to 20kHz, 5.2mVrms in) | 70.7dB | 70.0dB |

Signal-to-noise ratio (100W, A-weighted, max volume) | 79.2dB | 79.3dB |

THD (unweighted) | <0.0045% | <0.0045% |

THD+N (A-weighted) | <0.012% | <0.012% |

THD+N (unweighted) | <0.032% | <0.032% |

Our primary measurements revealed the following using the analog input at the headphone output (unless specified, assume a 1kHz sinewave, 2Vrms output, 300 ohms loading, 10Hz to 22.4kHz bandwidth):

Parameter | Left channel | Right channel |

Maximum output power into 600 ohms (1% THD+N, unweighted) | 93mW | 93mW |

Maximum output power into 300 ohms (1% THD+N, unweighted) | 183mW | 183mW |

Maximum output power into 32 ohms (1% THD+N, unweighted) | 238mW | 238mW |

Gain | 16.1dB | 15.9dB |

Output impedance | 3.2 ohms | 2.9 ohms |

Noise level (no signal, A-weighted) | <17uVrms | <15uVrms |

Noise level (no signal, 20Hz to 20kHz) | <21uVrms | <20uVrms |

Signal-to-noise ratio (Max Output, A-weighted, 2Vrms in) | 102.8dB | 103.6dB |

Signal-to-noise ratio (Max Output, 20Hz to 20kHz, 2Vrms in) | 100.4dB | 101.5dB |

THD ratio (unweighted) | *<0.33% | *<0.35% |

THD+N ratio (A-weighted) | <0.37% | <0.40% |

THD+N ratio (unweighted) | <0.33% | <0.35% |

*THD into 32 ohm load = 0.004%

**Frequency response (8-ohm loading, line-level input)**

In our measured frequency response chart above, the C 3050 LE is essentially flat within the audioband (20Hz to 20kHz), corroborating NAD’s claim of ±0.3dB. At the extremes the C 3050 LE is about 0.1dB down at 20Hz, and 0.15dB down at 20kHz. It is clear that the C 3050 LE digitizes the incoming analog signals because of the brickwall-type behavior just past 22kHz. The FFTs below also show that analog signals are sampled at 48kHz. In the graph above and most of the graphs below, only a single trace may be visible. This is because the left channel (blue or purple trace) is performing identically to the right channel (red or green trace), so they perfectly overlap, indicating that the two channels are ideally matched.

**Frequency response (8-ohm loading, line-level input, bass and treble controls)**

Above are frequency response plots measured at the speaker-level outputs into 8 ohms, with the bass and treble controls set to maximum (blue/red plots) and minimum (purple/green plots). We see that for the bass and treble controls, roughly +/-6dB and +/-5.5dB, respectively, of gain/cut are available at 20Hz and 20kHz.

**Frequency response vs. input type (8-ohm loading, left channel only)**

The chart above shows the C 3050 LE’s frequency response as a function of input type measured across the speaker outputs at 10W into 8 ohms. The green trace is the same analog input data from the previous graph. The blue trace is for a 16-bit/44.1kHz dithered digital input signal from 5Hz to 22kHz using the coaxial digital input, and the purple trace is for a 24/96 dithered digital input signal from 5Hz to 48kHz, while the pink trace is for a 24/192 dithered digital input signal from 5Hz to 96kHz. The 16/44.1 data exhibits brick-wall-type filtering, with a -3dB at 21.0kHz. The 24/96 and 24/192 kHz data yielded -3dB points at 46.1kHz and 71.8kHz, respectively. The analog input data yields a -3dB point at 22.9kHz, in line with a 48kHz sample rate.

**Frequency response with subwoofer-crossover engaged (120Hz, 8-ohm loading)**

Above are two frequency-response plots for the analog input, measured at 10W (8 ohms) at the speaker outputs, and at the line-level subwoofer output, with the crossover set at 120Hz and the subwoofer option enabled in the BluOS app. The C 3050 LE DSP crossover uses a slope of 18dB/octave.

**Frequency response (8-ohm loading, MM phono input)**

The chart above shows the frequency response for the MM phono input. What is shown is the deviation from the RIAA curve, where the input signal sweep is EQ’d with an inverted RIAA curve supplied by Audio Precision (*i.e.*, zero deviation would yield a flat line at 0dB). Here again we find sharp attenuating just past 22kHz, meaning the phono input is also digitized with a 48kHz sample rate. The very strict adherence to the RIAA curve likely means that EQ is applied in the digital domain.

**Phase response (MM input)**

Above is the phase-response plot from 20Hz to 20kHz for the MM phono input, measured across the speaker outputs at 10W into 8 ohms. The C 3050 LE does not invert polarity. For the phono input, since the RIAA equalization curve must be implemented, which ranges from +19.9dB (20Hz) to -32.6dB (90kHz), phase shift at the output is inevitable. Here we find a worst case of about -60 degrees at 200Hz and -40 degrees at 3kHz, and +40 degrees at 20Hz.

**Digital linearity (16/44.1 and 24/96 data)**

The chart above shows the results of a linearity test for the coaxial digital input for both 16/44.1 (blue/red) and 24/96 (purple/green) input data, measured at the line-level pre-outs of the C 3050 LE for a 1Vrms (at 0dBFS) output signal. The digital input is swept with a dithered 1kHz input signal from -120dBFS to 0dBFS, and the output is analyzed by the APx555. The ideal response would be a straight flat line at 0dB. In these tests, both data were essentially perfect as of -100dBFS down to 0dBFS. At -120dBFS, the 16/44.1 data were about +1.5/1dB (left/right) above reference, while the 24/96 data were within +1dB above reference. This is a good linearity test result.

**Impulse response (24/44.1 data)**

The graph above shows the impulse response for a looped 24/44.1 test file that moves from digital silence to full 0dBFS (all “1”s) for one sample period then back to digital silence, measured at the line-level pre-outs of C 3050 LE. We can see that the C 3050 LE utilizes a typical symmetrical sinc function reconstruction filter.

**J-Test (coaxial)**

The chart above shows the results of the J-Test test for the coaxial digital input measured at the line level pre-outs of the C 3050 LE. J-Test was developed by Julian Dunn in the 1990s. It is a test signal—specifically, a -3dBFS undithered 12kHz squarewave sampled (in this case) at 48kHz (24 bits). Since even the first odd harmonic (*i.e.*, 36kHz) of the 12kHz squarewave is removed by the bandwidth limitation of the sampling rate, we are left with a 12kHz sinewave (the main peak). In addition, an undithered 250Hz squarewave at -144dBFS is mixed with the signal. This test file causes the 22 least significant bits to constantly toggle, which produces strong jitter spectral components at the 250Hz rate and its odd harmonics. The test file shows how susceptible the DAC and delivery interface are to jitter, which would manifest as peaks above the noise floor at 500Hz intervals (*e.g.*, 250Hz, 750Hz, 1250Hz, etc.). Note that the alternating peaks are in the test file itself, but at levels of -144dBrA and below. The test file can also be used in conjunction with artificially injected sinewave jitter by the Audio Precision, to show how well the DAC rejects jitter.

The coaxial input exhibits low-level peaks in the audioband, around 6kHz and 18kHz on either side of the primary signal peak, at -125dBrA. This is a reasonably good J-Test result, indicating that the C 3050 LE DAC should yield good jitter immunity.

**J-Test (optical)**

The chart above shows the results of the J-Test test for the optical digital input measured at the line level pre-outs of the C 3050 LE. The optical input exhibits low-level peaks in the audioband, around 6kHz and 18kHz on either side of the primary signal peak, at -125dBrA. This is a reasonably good J-Test result, indicating that the C 3050 LE DAC should yield good jitter immunity.

**J-Test with 500ns of injected jitter (coaxial)**

Both the coaxial and optical inputs were also tested for jitter immunity by injecting 500ns of artificial sinewave jitter at 2kHz, which would manifest as sidebands at 10kHz and 14kHz without any jitter rejection. Jitter immunity proved exceptional, with no visible sidebands at a relatively high 500ns jitter level. The C 3050 LE DAC did lose sync with the signal when jitter was increased beyond 500ns. The optical input jitter result was very similar to the coaxial input result shown above.

**Wideband FFT spectrum of white noise and 19.1kHz sinewave tone (coaxial input)**

The plot above shows a fast Fourier transform (FFT) of the C 3050 LE’s line-level pre-outs with white noise at -4 dBFS (blue/red) and a 19.1 kHz sinewave at 0dBFS fed to the coaxial digital input, sampled at 16/44.1. The sharp roll-off above 20kHz in the white-noise spectrum shows the implementation of a brick-wall-type reconstruction filter. There are low-level aliased image peaks in the audioband at the -115dBrA and below level. The main 25kHz alias peak is near -60dBrA. The second, third and fourth distortion harmonics (38.2, 57.3, 76.4kHz) of the 19.1kHz tone are between -70dBrA and -90dBrA.

**RMS level vs. frequency vs. load impedance (1W, left channel only)**

The chart above shows RMS level (relative to 0dBrA, which is 1W into 8 ohms or 2.83Vrms) as a function of frequency, for the analog line-level input swept from 5Hz to 100kHz. The blue plot is into an 8-ohm load, the purple is into a 4-ohm load, the pink plot is an actual speaker (Focal Chora 806, measurements can be found here), and the cyan plot is no load connected. The chart below . . .

. . . is the same but zoomed in to highlight differences. Here we can see a maximum deviation within the audioband of a little more than 0.1dB from 4 ohms to no load, which is an indication of a mid-level damping factor, or mid to low output impedance. The maximum variation in RMS level when a real speaker was used is even less, deviating by just under 0.08dB.

**THD ratio (unweighted) vs. frequency vs. output power**

The chart above shows THD ratios at the output into 8 ohms as a function of frequency for a sinewave stimulus at the analog line-level input. The blue and red plots are for left and right channels at 1W output into 8 ohms, purple/green at 10W, and pink/orange near the rated 100W (about 95W). The power was varied using the volume control. At 1W and 10W, THD ratios were relatively flat and low at around 0.005%. The 95W THD values are higher and constant, just below 0.04%. These data did not quite corroborate NAD’s claim of 100W at 0.03% THD. We found that the 0.03% THD threshold was crossed at 92W.

**THD ratio (unweighted) vs. frequency at 10W (MM input)**

The chart above shows THD ratios as a function of frequency plots for the MM phono input measured across an 8-ohm load at 10W. The input sweep is EQ’d with an inverted RIAA curve. The THD values for the MM configuration vary from around 0.02% (20Hz) down to 0.003% at 6kHz.

**THD ratio (unweighted) vs. output power at 1kHz into 4 and 8 ohms**

The chart above shows THD ratios measured at the output of the C 3050 LE as a function of output power for the analog line-level input, for an 8-ohm load (blue/red for left/right channels) and a 4-ohm load (purple/green for left/right channels). Both data sets track fairly closely up to 20W or so, ranging from 0.002% to 0.005%. With an 8-ohm load, the “knee” occurs at about 100W, while the 4-ohm “knee” occurs at around 160W. The 1% THD values are reached at 111W (8 ohms) and 167W (4 ohms).

**THD+N ratio (unweighted) vs. output power at 1kHz into 4 and 8 ohms**

The chart above shows THD+N ratios measured at the output of the C 3050 LE as a function of output power for the analog line-level-input, for an 8-ohm load (blue/red for left/right channels) and a 4-ohm load (purple/green for left/right channels). Overall, THD+N values for both loads were similar, ranging from 0.01% down to 0.005%, with the 8-ohm data outperforming the 4-ohm data by about 2-5dB.

**THD ratio (unweighted) vs. frequency at 8, 4, and 2 ohms (left channel only)**

The chart above shows THD ratios measured at the output of the C 3050 LE as a function of frequency into three different loads (8/4/2 ohms) for a constant input voltage that yields 10W at the output into 8 ohms (and roughly 20W into 4 ohms, and 40W into 2 ohms) for the analog line-level input. The 8-ohm load is the blue trace, the 4-ohm load the purple trace, and the 2-ohm load the pink trace. We find roughly the same THD values of 0.02% to 0.01% for the 4- and 2-ohm data. This is a strong result and shows the C 3050 LE is stable into 2- ohms loads. For the 8-ohm data, THD ratios are lower, and also fairly constant at around 0.01-0.005%.

**THD ratio (unweighted) vs. frequency into 8 ohms and real speakers (left channel only)**

The chart above shows THD ratios measured at the output of the C 3050 LE as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). From 400Hz to 6kHz, all three loads yield identical 0.005% THD ratios. At lower frequencies, the two-way speaker yielded the highest THD ratios, as high as 0.07% at 20Hz, but as low as 0.002% at 50Hz. The three-way speaker ranged from a high of 0.01% at 30Hz, down to 0.002% at 40Hz.

**IMD ratio (CCIF) vs. frequency into 8 ohms and real speakers (left channel only)**

The chart above shows intermodulation distortion (IMD) ratios measured at the output of the C 3050 LE as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. Here the CCIF IMD method is used, where the primary frequency is swept from 20kHz (F1) down to 2.5kHz, and the secondary frequency (F2) is always 1kHz lower than the primary, with a 1:1 ratio. The CCIF IMD analysis results are the sum of the second (F1-F2 or 1kHz) and third modulation products (F1+1kHz, F2-1kHz). The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). All three results are similar, with IMD ratios from as low as 0.005% up to 0.04% at 20kHz.

**IMD ratio (SMPTE) vs. frequency into 8 ohms and real speakers (left channel only)**

The chart above shows IMD ratios measured at the output of the C 3050 LE as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. Here, the SMPTE IMD method is used, where the primary frequency (F1) is swept from 250Hz down to 40Hz, and the secondary frequency (F2) is held at 7kHz with a 4:1 ratio. The SMPTE IMD analysis results consider the second (F2 ± F1) through the fifth (F2 ± 4xF1) modulation products. The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a two-way speaker (Paradigm Founder Series 100F, measurements can be found here). All three results are nearly identical, with flat IMD results just over 0.01%.

**FFT spectrum – 1kHz (line-level input)**

Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the analog line-level input. We see that the signal’s second and third harmonics, at 2 and 3kHz, are around -90dBrA, or 0.003%. The subsequent signal harmonics are around or below -110dBrA, or 0.0003%. There are low-level power supply related noise peaks (60Hz, 180Hz, 300Hz) on the left side of the main 1kHz peak, at -120dBrA, or 0.0001%. There is also a rise in the noise above 20kHz, characteristic of digital amplifiers. Also visible are the IMD products between the 48kHz sample rate used to digitize the analog signal and the 1kHz signal, at 47kHz and 49kHz.

**FFT spectrum – 1kHz (digital input, 16/44.1 data at 0dBFS)**

Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the coaxial digital input, sampled at 16/44.1. The second (2kHz) signal harmonic is at -105dBrA, or 0.0006%, while the third (3kHz) signal harmonic is at -85dBrA, or 0.006%. Noise-related peaks are the same as the analog FFT above.

**FFT spectrum – 1kHz (digital input, 24/96 data at 0dBFS)**

Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the coaxial digital input, sampled at 24/96. Within the audioband, the FFT is essentially identical as the 16/44.1 FFT above, except for a slightly lower noise floor due to higher bit depth.

**FFT spectrum – 1kHz (digital input, 16/44.1 data at -90dBFS)**

Shown above is the FFT for a 1kHz, -90dBFS, dithered, 16/44.1 input sinewave stimulus at the coaxial digital input, measured at the output across an 8-ohm load. We see the 1kHz primary signal peak, at the correct amplitude, and a signal harmonic at 6kHz. The noise floor on the right channel is much higher, at -130dBrA, than the left channel, at just above -160dBrA.

**FFT spectrum – 1kHz (digital input, 24/96 data at -90dBFS)**

Shown above is the FFT for a 1kHz, -90dBFS, dithered, 24/96 input sinewave stimulus at the coaxial digital input, measured at the output across an 8-ohm load. We see the 1kHz primary signal peak, at the correct amplitude, and a signal harmonic at 6kHz. As with the chart above, the noise floor on the right channel is much higher, at -130dBrA, than the left channel, at -160dBrA.

**FFT spectrum – 1kHz (MM phono input)**

Shown above is the FFT for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the MM phono input. The second (2kHz) signal harmonic is at -100dBrA, or 0.001%, while the third (3kHz) signal harmonic is at -90dBrA, or 0.003%. We see the primary (60Hz) power-supply related peak at -80dBrA, or 0.01%, and subsequent odd-order power-supply related peaks (180, 300, 420Hz, etc.) extending beyond the 1kHz signal peak, at -80 down to -120dBrA, or 0.01 down to 0.0001%.

**FFT spectrum – 50Hz (line-level input)**

Shown above is the FFT for a 50Hz input sinewave stimulus measured at the output across an 8-ohm load at 10W for the analog line-level input. The X axis is zoomed in from 40Hz to 1kHz, so that peaks from noise artifacts can be directly compared against peaks from the harmonics of the signal. The second (100Hz) and third (150Hz) signal harmonics are at -90dBrA, or 0.003%. We also see odd harmonics of the 60Hz power-supply-related peak (180Hz, 300Hz, 420Hz) at -115dBrA, or 0.0002%, and below.

**FFT spectrum – 50Hz (MM phono input)**

Shown above is the FFT for a 50Hz input sinewave stimulus measured at the output across an 8-ohm load at 10W for the MM phono input. The X axis is zoomed in from 40 Hz to 1kHz, so that peaks from noise artifacts can be directly compared against peaks from the harmonics of the signal. The most predominant (non-signal) peaks are from the 60Hz power-supply fundamental and its third harmonic at -80dBrA, or 0.01%. The signal’s second harmonic (100Hz) is at -100/-95dBrA (left/right), or 0.001/0.002%.

**Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, line-level input)**

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the output across an 8-ohm load at 10W for the analog line-level input. The input RMS values are set at -6.02dBrA so that, if summed for a mean frequency of 18.5kHz, would yield 10W (0dBrA) into 8 ohms at the output. We find that the second-order modulation product (*i.e.*, the difference signal of 1kHz) is at -100/-110dBrA (left/right channels), or 0.001/0.0003%. The third-order modulation products, at 17kHz and 20kHz, are around -80dBrA, or 0.01%. There are also a multitude of peaks throughout the FFT, at -100dBrA and below. This could certainly not be described as a clean IMD FFT. We also see the main aliased peaks at 29kHz and 30kHz around -70dBrA due to the 48kHz sample rate (48kHz-19kHz = 29kHz).

**Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, coaxial digital input, 16/44.1)**

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the output across an 8-ohm load at 10W for the digital coaxial input at 16/44.1. We find that the second-order modulation product (*i.e.*, the difference signal of 1kHz) is at -100/-110dBrA (left/right channels), or 0.001/0.0003%. The third-order modulation products, at 17kHz and 20kHz, are around -80dBrA, or 0.01%. We also see the main aliased peaks at 25.1kHz and 26.1kHz around -70dBrA due to the 44.1kHz sample rate (44.1kHz-19kHz = 25.1kHz).

**Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, coaxial digital input, 24/96)**

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the output across an 8-ohm load at 10W for the digital coaxial input at 24/96. We find that the second-order modulation product (*i.e.*, the difference signal of 1kHz) is at -100/-110dBrA (left/right channels), or 0.001/0.0003%. The third-order modulation products, at 17kHz and 20kHz, are around -80dBrA, or 0.01%. There are also many peaks throughout the FFT, at -100dBrA and below. This could certainly not be described as a clean IMD FFT.

**Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, MM phono input)**

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the output across an 8-ohm load at 10W for the MM phono input. We find that the second-order modulation product (*i.e.*, the difference signal of 1kHz) is at around -105dBRa, or 0.0006%, while the third-order modulation products, at 17kHz and 20kHz, are around -90dBrA, or 0.003%.

**Square-wave response (10kHz)**

Above is the 10kHz squarewave response using the analog line-level input, at roughly 10W into 8 ohms. Due to limitations inherent to the Audio Precision APx555 B Series analyzer, this graph should not be used to infer or extrapolate the C 3050 LE’s slew-rate performance. Rather, it should be seen as a qualitative representation of the C 3050 LE’s very restricted bandwidth. An ideal squarewave can be represented as the sum of a sinewave and an infinite series of its odd-order harmonics (*e.g.*, 10kHz + 30kHz + 50kHz + 70kHz . . .). A limited bandwidth will show only the sum of the lower-order harmonics, which may result in noticeable undershoot and/or overshoot, and softening of the edges. Here we can see only the 10kHz fundamental (due to the digitization of the incoming signal with a 48kHz sample rate resulting in a 22kHz bandwidth), plus the 400kHz switching oscillator frequency used in the digital amplifier section, which is visibly modulating the waveform.

**Square-wave response (1kHz, restricted 250kHz bandwidth)**

Above is the 1kHz squarewave response using the analog line-level input, at roughly 10W into 8 ohms, this time with a 250kHz input bandwidth on the analyzer to filter out the 400kHz switching frequency. We see more evidence here, in the over/undershoot and soft corners of the squarewave, of the C 3050 LE’s low bandwidth with an analog input.

**FFT spectrum (1MHz bandwidth)**

The C 3050 LE’s class-D amplifier relies on a switching oscillator to convert the input signal to a pulse-width modulated (PWM) squarewave (on/off) signal before sending the signal through a low-pass filter to generate an output signal. The C 3050 LE oscillator switches at a rate of about 400kHz, and this graph plots a wide bandwidth FFT spectrum of the amplifier’s output at 10W into 8 ohms as it’s fed a 1kHz sinewave. We can see that the 400kHz peak is quite evident, and at -35dBrA. There are also two peaks at 800kHz and 1.2MHz (the second and third harmonic of the 400kHz peak), at -60 and -90dBrA. Those peaks—the fundamental and its harmonics—are direct results of the switching oscillators in the C 3050 LE amp modules. The noise around those very-high-frequency signals are in the signal, but all that noise is far above the audio band—and therefore inaudible—and so high in frequency that any loudspeaker the amplifier is driving should filter it all out anyway.

**Damping factor vs. frequency (20Hz to 20kHz)**

The final graph above is the damping factor as a function of frequency. Both channels show a relatively constant damping factor from 20Hz to 20kHz, ranging from 200/244 (left/right channels) up to 213/266 (left/right channels) at 20kHz. This is a mid-tier-level damping-factor result.

*Diego Estan*

Electronics Measurement Specialist

- Details
- Parent Category: Products
- Category: Amplifier Measurements

Link: reviewed by Roger Kanno on *SoundStage! Hi-Fi* on February 1, 2023

**General Information**

All measurements taken using an Audio Precision APx555 B Series analyzer.

The Rotel Diamond Series RA-6000 was conditioned for 1 hour at 1/8th full rated power (~25W into 8 ohms) before any measurements were taken. All measurements were taken with both channels driven, using a 120V/20A dedicated circuit, unless otherwise stated.

The Rotel RA-6000 offers three line-level analog inputs (RCA), one balanced line-level analog input (XLR), one phono input for moving magnet (MM) cartridges (RCA), pre-outs and sub-outs that operate identically (both RCA), three S/PDIF coaxial inputs (RCA), two S/PDIF optical inputs (TosLink), one USB input, one Bluetooth input, two separate (A and B) speaker-level outputs, and one headphone output (1/8″ TRS).

For the purposes of these measurements, the following inputs were evaluated: S/PDIF digital coaxial (RCA), analog line-level (XLR), and MM phono (RCA). Unless otherwise stated, the tone controls were bypassed. The only difference between the analog RCA and XLR inputs is 6dB less gain over the balanced XLR inputs. That is to say, to achieve the same output power at the speaker outputs using a 2Vrms input over then RCA input, 4Vrms is required over the balanced inputs.

Most measurements were made with a 4Vrms line-level signal at the analog input, 5mVrms at the MM input, and 0dBFS at the digital input. The volume display is variable between 0 and 96. To achieve 10W at the speaker outputs with the input values stipulated, the volume position required for the XLR input was 67, but 65 for the digital input and 70 for the phono input. The signal-to-noise ratio (SNR) measurements were made with the same input signal values but with the volume set to achieve the rated output power of 200W into 8 ohms. For comparison, on the line-level input, a SNR measurement was also made with the volume at maximum, where only 0.219Vrms was required to achieve 70W into 8 ohms.

Based on the high accuracy and low variability of the left/right volume channel matching (see table below), the RA-6000 volume control is likely digitally controlled but operating in the analog domain. The RA-6000 offers between 5 and 2dB volume steps between volume positions 1 and 7, and then 1dB steps up to position 76, then 0.5dB stepss up to the maximum level (96). Overall range is -52dB to +27.9dB (line-level RCA input, speaker output). Note that throughout the volume range, many volume steps were unused. For example, step 7 and step 8 had the same level of attenuation.

**Volume-control accuracy (measured at speaker outputs): left-right channel tracking**

Volume position | Channel deviation |

1 | 0.388dB |

10 | 0.269dB |

30 | 0.216dB |

50 | 0.217dB |

70 | 0.134dB |

80 | 0.083dB |

96 | 0.068dB |

**Published specifications vs. our primary measurements**

The table below summarizes the measurements published by Rotel for the RA-6000 compared directly against our own. The published specifications are sourced from Rotel’s website, either directly or from the manual available for download, or a combination thereof. With the exception of frequency response, where the Audio Precision bandwidth was extended to 500kHz, assume, unless otherwise stated, 10W into 8 ohms and a measurement input bandwidth of 10Hz to 90kHz, and the worst-case measured result between the left and right channels.

Parameter | Manufacturer | SoundStage! Lab |

Rated output power into 8 ohms (1% THD, 1kHz) | 200W | 225W |

Rated output power into 4 ohms (1% THD, 1kHz) | 350W | 374W |

THD (1kHz, 10W, 8 ohms) | <0.0075% | <0.0026% |

SNR (A-weighted, 8 ohms, line-level input) | 103dB | 101dB |

SNR (A-weighted, 8 ohms, digital input 24/96) | 102dB | 101dB |

SNR (A-weighted, 8 ohms, phono input) | 80dB | 86dB |

Damping factor (ref. 8 ohms 1kHz) | 600 | 637 |

Frequency response (line-level input) | 10Hz-100kHz, ±0.5dB | 10Hz-100kHz, -0.4,+0.2dB |

Frequency response (digital input, 24/192) | 10Hz-90kHz, ±2dB | 10Hz-90kHz, -1.8,-1.5dB |

Frequency response (phono input) | 20Hz-20kHz, ±0.5dB | 20Hz-20kHz, ±0.5dB |

Intermodulation distortion (60Hz:7kHz, 4:1, 10W into 8ohms) | <0.03% | <0.015% |

Input sensitivity (line-level, RCA) | 340mVrms | 1.6Vrms |

Input sensitivity (line-level, XLR) | 540mVrms | 3.1Vrms |

Input sensitivity (digital) | 0dBFS | -4.1dBFS |

Input sensitivity (phono) | 5.2mVrms | 6.2mVrms |

Input impedance (line-level, RCA) | 5.6k ohms | 6.6k ohms |

Input impedance (line-level, XLR) | 100k ohms | 117k ohms |

Input impedance (phono) | 47k ohms | 54.9k ohms |

Input overload (line-level, RCA) | 3.5Vrms | 4.0Vrms |

Input overload (line-level, XLR) | 4.5Vrms | 4.9Vrms |

Input overload (phono, 1kHz) | 52mVrms | 72mVrms |

Output impedance (pre-out) | 100 ohms | 101 ohms |

Our primary measurements revealed the following using the balanced line-level analog input and digital coaxial input (unless specified, assume a 1kHz sinewave at 2Vrms or 0dBFS, 10W output, 8-ohm loading, 10Hz to 90kHz bandwidth):

Parameter | Left channel | Right channel |

Maximum output power into 8 ohms (1% THD+N, unweighted) | 225W | 225W |

Maximum output power into 4 ohms (1% THD+N, unweighted) | 374W | 374W |

Maximum burst output power (IHF, 8 ohms) | 253.8W | 253.8W |

Maximum burst output power (IHF, 4 ohms) | 453.0W | 453.0W |

Continuous dynamic power test (5 minutes, both channels driven) | passed | passed |

Crosstalk, one channel driven (10kHz) | -75.6dB | -65.3dB |

Damping factor | 637 | 737 |

Clipping no-load output voltage (instantaneous power into 8 ohms) | 50Vrms | 50Vrms |

DC offset | <1mV | <5.7mV |

Gain (pre-amp section) | 1.3dB | 1.3dB |

Gain (maximum volume) | 27.9dB | 27.9dB |

IMD ratio (CCIF, 18kHz + 19kHz stimulus tones, 1:1) | <-92dB | <-92dB |

IMD ratio (SMPTE, 60Hz + 7kHz stimulus tones, 4:1 ) | <-82dB | <-82dB |

Input impedance (line input, RCA) | 6.6k ohms | 6.6k ohms |

Input impedance (line input, XLR) | 112k ohms | 117k ohms |

Input sensitivity (for rated power, maximum volume) | 3.1Vrms | 3.1Vrms |

Noise level (A-weighted) | <0.37mVrms | <0.37mVrms |

Noise level (unweighted) | <0.9mVrms | <0.9mVrms |

Output impedance (pre-out) | 100 ohms | 101 ohms |

Signal-to-noise ratio (full power, A-weighted, 4Vrms in) | 100.8dB | 100.9dB |

Signal-to-noise ratio (full power, unweighted, 4Vrms in) | 92.8dB | 92.9dB |

Signal-to-noise ratio (full power, A-weighted, max volume) | 100.6dB | 100.8dB |

Dynamic range (full power, A-weighted, digital 24/96) | 100.8dB | 100.7dB |

Dynamic range (full power, A-weighted, digital 16/44.1) | 94.6dB | 94.7dB |

THD ratio (unweighted) | <0.0019% | <0.0026% |

THD ratio (unweighted, digital 24/96) | <0.0023% | <0.0031% |

THD ratio (unweighted, digital 16/44.1) | <0.0023% | <0.0031% |

THD+N ratio (A-weighted) | <0.0045% | <0.0049% |

THD+N ratio (A-weighted, digital 24/96) | <0.0048% | <0.0053% |

THD+N ratio (A-weighted, digital 16/44.1) | <0.0072% | <0.0075% |

THD+N ratio (unweighted) | <0.011% | <0.011% |

Minimum observed line AC voltage | 124VAC | 124VAC |

For the continuous dynamic power test, the RA-6000 was able to sustain 400W into 4 ohms (~3% THD) using an 80Hz tone for 500ms, alternating with a signal at -10dB of the peak (40W) for 5 seconds, for 5 continuous minutes without inducing a fault or the initiation of a protective circuit. This test is meant to simulate sporadic dynamic bass peaks in music and movies. During the test, the top of the RA-6000 was hot the touch, causing discomfort.

Our primary measurements revealed the following using the phono-level input, MM configuration (unless specified, assume a 1kHz 5mVrms sinewave input, 10W output, 8-ohm loading, 10Hz to 90kHz bandwidth):

Parameter | Left channel | Right channel |

Crosstalk, one channel driven (10kHz) | -75.9dB | -59.5dB |

DC offset | <1m | mV |

Gain (default phono preamplifier) | 48.3dB | 48.3dB |

IMD ratio (CCIF, 18kHz + 19kHz stimulus tones, 1:1) | <-88dB | <-88dB |

IMD ratio (CCIF, 3kHz + 4kHz stimulus tones, 1:1) | <-86dB | <-86dB |

Input impedance | 54.9k ohms | 53.6k ohms |

Input sensitivity (to max power with max volume) | 6.2mVrms | 6.25mVrms |

Noise level (A-weighted) | <0.9mVrms | <0.9mVrms |

Noise level (unweighted) | <2.8mVrms | <2.8mVrms |

Overload margin (relative 5mVrms input, 1kHz) | 23.2dB | 23.2dB |

Signal-to-noise ratio (full rated power, A-weighted) | 85.9dB | 86.0dB |

Signal-to-noise ratio (full rated power, unweighted) | 78.8dB | 78.5dB |

THD (unweighted) | <0.0019% | <0.0018% |

THD+N (A-weighted) | <0.01% | <0.01% |

THD+N (unweighted) | <0.03% | <0.03% |

Our primary measurements revealed the following using the analog input at the headphone output (unless specified, assume a 1kHz 2Vrms sinewave input (RCA), 2Vrms output, 300 ohms loading, 10Hz to 90kHz bandwidth):

Parameter | Left channel | Right channel |

Maximum output power into 600 ohms (1% THD+N, unweighted) | 871mW | 871mW |

Maximum output power into 300 ohms (1% THD+N, unweighted) | 750mW | 750mW |

Maximum output power into 32 ohms (1% THD+N, unweighted) | 133mW | 133mW |

Gain | 27.8dB | 27.9dB |

Output impedance | 673 ohms | 673 ohms |

Noise level (A-weighted) | <103uVrms | <103uVrms |

Noise level (unweighted) | <363uVrms | <341uVrms |

Signal-to-noise ratio (A-weighted, ref. max output voltage) | 102.5dB | 102.8dB |

Signal-to-noise ratio (unweighted, ref. max output voltage) | 92.1dB | 92.6dB |

THD ratio (unweighted) | <0.0018% | <0.0018% |

THD+N ratio (A-weighted) | <0.0053% | <0.0053% |

THD+N ratio (unweighted) | <0.018% | <0.016% |

**Frequency response (8-ohm loading, line-level input)**

In our frequency response plots above, measured across the speaker outputs at 10W into 8 ohms, the RA-6000 is near perfectly flat within the audioband (-0.2/0dB, 20Hz/20kHz). At the extremes, the RA-6000 is at -1.5dB at 5Hz and +0.7dB at 200kHz, making “wide bandwidth audio amplifier” an apt descriptor for the RA-6000. Rotel’s claim of 10Hz-100kHz, ±0.5dB, is not quite corroborated, as we measured -0.5dB at 10Hz and about +0.2dB at 100kHz. In the graph above and most of the graphs below, only a single trace may be visible. This is because the left channel (blue or purple trace) is performing identically to the right channel (red or green trace), and so they perfectly overlap, indicating that the two channels are ideally matched.

**Frequency response (8-ohm loading, line-level input, bass and treble controls)**

Above is a frequency response plot measured at the speaker-level outputs into 8 ohms, with the bass and treble controls set to maximum (blue/red plots) and minimum (purple/green plots). We see that for the bass and treble controls, roughly +/-12dB of gain/cut is available at 20Hz and roughly +/-9dB of gain/cut at 20kHz.

**Phase response (8-ohm loading, line-level input)**

Above are the phase response plots from 20Hz to 20kHz for the line-level input, measured across the speaker outputs at 10W into 8 ohms. The RA-6000 does not invert polarity and exhibits, at worst, about 30 degrees (at 20kHz) of phase shift within the audioband.

**Frequency response vs. input type (8-ohm loading, left channel only)**

The chart above shows the RA-6000’s frequency response as a function of input type measured across the speaker outputs at 10W into 8 ohms. The green trace is the same analog input data from the previous graph (but limited to 80kHz). The blue trace is for a 16-bit/44.1kHz dithered digital input signal from 5Hz to 22kHz using the coaxial input, the purple trace is for a 24/96 dithered digital input signal from 5Hz to 48kHz, while the pink trace is for a 24/192 dithered digital input signal from 5Hz to 96kHz. At low frequencies, the analog input exhibits a more extended response, measuring -0.5dB at 10Hz, whereas the digital inputs are at -1.7dB at 10Hz. At high frequencies, the 16/44.1 data exhibits brickwall-type filtering, with a -3dB point at 21.0kHz. The 24/96 and 24/192 kHz data yielded -3dB points at 46.3kHz and 92kHz, respectively.

**Frequency response (8-ohm loading, MM phono input)**

The chart above shows the frequency response for the phono input (MM). What is shown is the deviation from the RIAA curve, where the input signal sweep is EQ’d with an inverted RIAA curve supplied by Audio Precision (*i.e.*, zero deviation would yield a flat line at 0dB). We see a maximum deviation within the audioband of about +0.5dB at 40kHz.

**Phase response (MM input)**

Above is the phase response plot from 20Hz to 20kHz for the phono input (MM), measured across the speaker outputs at 10W into 8 ohms. The RA-6000 does not invert polarity. For the phono input, since the RIAA equalization curve must be implemented, which ranges from +19.9dB (20Hz) to -32.6dB (90kHz), phase shift at the output is inevitable. Here we find a worst case of about -60 degrees at 200Hz and 5kHz.

**Digital linearity (16/44.1 and 24/96 data)**

The chart above shows the results of a linearity test for the coaxial digital input for both 16/44.1 (blue/red) and 24/96 (purple/green) input data, measured at the line-level output of the RA-6000. The digital input is swept with a dithered 1kHz input signal from -120dBFS to 0dBFS, and the output is analyzed by the APx555. The ideal response would be a straight flat line at 0dB. Both data were essentially perfect as of -90dBFS down to 0dBFS. At -120dBFS, the 16/44.1 data were +4dB above reference, while the 24/96 data were +1/+7.5dB (left/right) above reference. This is a relatively poor linearity test result.

**Impulse response (24/44.1 data)**

The graph above shows the impulse responses for the RA-6000, fed to the coaxial digital input, measured at the line-level output, for a looped 24/44.1 test file that moves from digital silence to full 0dBFS (all “1”s), for one sample period then back to digital silence. We find a symmetrical sinc function type of impulse response.

**J-Test (coaxial)**

The chart above shows the results of the J-Test test for the coaxial digital input measured at the line-level output of the RA-6000. J-Test was developed by Julian Dunn in the 1990s. It is a test signal: specifically, a -3dBFS undithered 12kHz squarewave sampled (in this case) at 48kHz (24 bits). Since even the first odd harmonic (*i.e.*, 36kHz) of the 12kHz squarewave is removed by the bandwidth limitation of the sampling rate, we are left with a 12kHz sinewave (the main peak). In addition, an undithered 250Hz squarewave at -144dBFS is mixed with the signal. This test file causes the 22 least significant bits to constantly toggle, which produces strong jitter spectral components at the 250Hz rate and its odd harmonics. The test file shows how susceptible the DAC and delivery interface are to jitter, which would manifest as peaks above the noise floor at 500Hz intervals (*e.g,*, 250Hz, 750Hz, 1250Hz, etc.). Note that the alternating peaks are in the test file itself, but at levels of -144dBrA and below. The test file can also be used in conjunction with artificially injected sinewave jitter by the Audio Precision, to show how well the DAC rejects jitter.

The coaxial input exhibits obvious peaks throughout the audioband, as high as -95dBrA on both sides of the 12kHz fundamental. This is a relatively poor J-Test result, indicating that RA-6000 DAC may be susceptible to jitter through this input.

**J-Test (optical)**

The chart above shows the results of the J-Test test for the optical digital input measured at the line-level output of the RA-6000. The result is much cleaner than for the coaxial input. The highest peaks are just below -110dBrA, on both sides of the 12kHz fundamental. This input may be less susceptible to jitter.

**J-Test with 10ns of injected jitter (coaxial)**

The coaxial input was also tested for jitter immunity by injecting artificial sinewave jitter at 2kHz, which would manifest as sidebands at 10kHz and 14kHz without any jitter rejection. Jitter immunity proved poor, as predicted because of the above J-Test result, with visible sidebands at only the 10ns jitter level, at -70dBrA.

**J-Test with 100ns of injected jitter (coaxial)**

The coaxial input was also tested for jitter immunity by injecting artificial sinewave jitter at 2kHz, which would manifest as sidebands at 10kHz and 14kHz without any jitter rejection. Jitter immunity proved poor, as predicted because of the other results, with visible sidebands at the 100ns jitter level, at -50dBrA. The optical input (not shown) performed similarly with the same 100ns jitter level injected.

**Wideband FFT spectrum of white noise and 19.1kHz sine-wave tone (coaxial input)**

The chart above shows a fast Fourier transform (FFT) of the RA-6000’s line-level output with white noise at -4dBFS (blue/red) and a 19.1kHz sinewave at 0dBFS fed to the coaxial digital input, sampled at 16/44.1. The steep roll-off around 20kHz in the white-noise spectrum shows the behavior of the RA-6000’s reconstruction filter. There are no aliased image peaks within the audioband visible above the -120dBrA noise floor. The primary aliasing signal at 25kHz is at -60dBrA, while the second and third distortion harmonics (38.2, 57.3kHz) of the 19.1kHz tone are at -75dBrA and below.

**RMS level vs. frequency vs. load impedance (1W, left channel only)**

The chart above shows RMS level (relative to 0dBrA, which is 1W into 8ohms or 2.83Vrms) as a function of frequency, for the analog line-level input swept from 5Hz to 100kHz. The blue plot is into an 8-ohm load, the purple is into a 4-ohm load, the pink plot is an actual speaker (Focal Chora 806, measurements can be found here), and the cyan plot is no load connected. The chart below . . .

. . . is the same but zoomed in to highlight differences. Here we find that the maximum deviation between no-load and a 4-ohm load is very small, at just below 0.04dB. This is an indication of a very high damping factor, or low output impedance. With a real speaker, maximum deviations in RMS level were slightly smaller.

**THD ratio (unweighted) vs. frequency vs. output power**

The chart above shows THD ratios at the output into 8 ohms as a function of frequency for a sinewave stimulus at the analog line-level input. The blue and red plots are for left and right channels at 1W output into 8 ohms, purple/green at 10W, and pink/orange at 200W. Power was varied using the volume control. We find exceptionally consistent THD ratios at all power levels. THD ratios ranged from 0.005-0.01% at 20Hz, down to 0.002% between 100 and 500Hz, then up to 0.02-0.03% at 20Hz. Between all three power levels, a worst case of about 5dB of THD difference was observed.

**THD ratio (unweighted) vs. frequency at 10W (MM input)**

The chart above shows THD ratios as a function of frequency plots for the phono input measured across an 8-ohm load at 10W. The input sweep is EQ’d with an inverted RIAA curve. THD values vary from around 0.05% (20Hz), down to 0.001% (1kHz), then up to 0.03% (20kHz).

**THD ratio (unweighted) vs. output power at 1kHz into 4 and 8 ohms**

The chart above shows THD ratios measured at the output of the RA-6000 as a function of output power for the analog line-level input, for an 8-ohm load (blue/red for left/right channels) and a 4-ohm load (purple/green for left/right channels). The 8-ohm data ranged from about 0.01% at 50mW, down to 0.0015% at 50W, to the “knee,” which is just shy of 200W. The 4-ohm data yielded THD ratios roughly 5dB higher, and hit the “knee” at just over 300W. The 1% THD marks were hit at 225W (8 ohms) and 374W (4 ohms).

**THD+N ratio (unweighted) vs. output power at 1kHz into 4 and 8 ohms**

The chart above shows THD+N ratios measured at the output of the RA-6000 as a function of output power for the analog line-level input, for an 8-ohm load (blue/red for left/right channels) and a 4-ohm load (purple/green for left/right channels). THD+N values for the 8-ohm data ranged from 0.015%, down to 0.003% at the “knee.” The 8-ohm data outperformed the 4-ohm data by 3-4dB.

**THD ratio (unweighted) vs. frequency at 8, 4, and 2 ohms (left channel only)**

The chart above shows THD ratios measured at the output of the RA-6000 as a function of frequency into three different loads (8/4/2 ohms) for a constant input voltage that yields 20W at the output into 8 ohms (and roughly 40W into 4 ohms, and 80W into 2 ohms) for the analog line-level input. The 8-ohm load is the blue trace, the 4-ohm load the purple trace, and the 2-ohm load the pink trace. We see increasing levels (5-10dB) of THD from 8 to 4 to 2 ohms. Even into 2 ohms, however, THD ratios ranged from 0.05% down to 0.007%. Overall, this is a good result and shows how stable the RA-6000 is into low impedances.

**THD ratio (unweighted) vs. frequency into 8 ohms and real speakers (left channel only)**

The chart above shows THD ratios measured at the output of the RA-6000 as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the balanced analog line-level input. The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). There are deviations in THD ratios above 6kHz, where the three-way speaker yielded the highest results (0.02% at 20Hz), the two-way speaker the lowest results (0.005% at 20kHz), and the 8-ohm dummy load in between (0.01% at 20kHz). For the rest of the audioband, all three THD results are fairly close to another, ranging from 0.01-0.02% at 20Hz, down to 0.002% around 1kHz. This is a testament to the RA-6000’s robust power supply and high damping factor.

**IMD ratio (CCIF) vs. frequency into 8 ohms and real speakers (left channel only)**

The chart above shows intermodulation distortion (IMD) ratios measured at the output of the RA-6000 as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. Here the CCIF IMD method is used, where the primary frequency is swept from 20kHz (F1) down to 2.5kHz, and the secondary frequency (F2) is always 1kHz lower than the primary, with a 1:1 ratio. The CCIF IMD analysis results are the sum of the second (F1-F2 or 1kHz) and third modulation products (F1+1kHz, F2-1kHz). The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). All three data sets track fairly closely, with the expection of the three-way speaker showing higher IMD values above 10kHz, differing by about 5dB at 20kHz. Overall, IMD ratios were hovering around 0.002 to 0.003%.

**IMD ratio (SMPTE) vs. frequency into 8 ohms and real speakers (left channel only)**

The chart above shows IMD ratios measured at the output of the RA-6000 as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. Here, the SMPTE IMD method is used, where the primary frequency (F1) is swept from 250Hz down to 40Hz, and the secondary frequency (F2) is held at 7kHz with a 4:1 ratio. The SMPTE IMD analysis results consider the second (F2 ± F1) through the fifth (F2 ± 4xF1) modulation products. The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). All three data sets are close enough to be judged as identical, hovering just below the 0.032% mark.

**FFT spectrum – 1kHz (line-level input)**

Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the analog line-level input. We see that the signal’s second harmonic, at 2kHz, is at -95dBrA, or 0.002%, while all subsequent harmonics are below the -105dBrA level, or 0.0006% mark. Power-supply-related noise at the fundamental frequency (60Hz), as well as both even and odd harmonics, are evident, at -100dBrA, or 0.001%, levels and below.

**FFT spectrum – 1kHz (digital input, 16/44.1 data at 0dBFS)**

Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the coaxial digital input, sampled at 16/44.1. Signal harmonics and power-supply-related noise peaks are very similar in level to the analog input FFT above, with the exception of the large peaks just below 50 and 100kHz, which are IMD products of the 44.1kHz sample rate and signal (43.1kHz and 45.1kHz), and their resultant second harmonics.

**FFT spectrum – 1kHz (digital input, 24/96 data at 0dBFS)**

Shown above is the fast Fourier transform (FFT) for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the coaxial digital input, sampled at 24/96. Signal harmonics and power supply related noise peaks are very similar in level to the analog input FFT above, except here the IMD products of the 96kHz sample rate and signal (95kHz and 97kHz) are visible.

**FFT spectrum – 1kHz (digital input, 16/44.1 data at -90dBFS)**

Shown above is the FFT for a 1kHz -90dBFS dithered 16/44.1 input sinewave stimulus at the coaxial digital input, measured at the output across an 8-ohm load. We see the 1kHz primary signal peak, at the correct amplitude, and low-level power-supply-related noise harmonics at -110dBrA, or 0.0003%, and below.

**FFT spectrum – 1kHz (digital input, 24/96 data at -90dBFS)**

Shown above is the FFT for a 1kHz -90dBFS dithered 24/96 input sinewave stimulus at the coaxial digital input, measured at the output across an 8-ohm load. We see the 1kHz primary signal peak, at the correct amplitude, and power-supply-related noise harmonics at -110dBrA, or 0.0003%, and below.

**FFT spectrum – 1kHz (MM phono input)**

Shown above is the FFT for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the MM phono input. We see the second (2kHz) signal harmonics at -100/105dBrA (left/right), or 0.001% and 0.0006%. Higher-order signal harmonics are below the -110dBrA level, or 0.0003%, and difficult to distinguish amongst the high-order power-supply-related noise peaks. Power-supply-related peaks can be seen throughout, with the highest at the third harmonic (180Hz) at -85/-90dBrA (left/right channels), or 0.006/0.003%.

**FFT spectrum – 50Hz (line-level input)**

Shown above is the FFT for a 50Hz input sinewave stimulus measured at the output across an 8-ohm load at 10W for the analog line-level input. The X axis is zoomed in from 40Hz to 1kHz, so that peaks from noise artifacts can be directly compared against peaks from the harmonics of the signal. Power-supply-related and signal-related peaks can be seen at and below -100dBrA, or 0.001%.

**FFT spectrum – 50Hz (MM phono input)**

Shown above is the FFT for a 50Hz input sinewave stimulus measured at the output across an 8-ohm load at 10W for the MM phono input. The X axis is zoomed in from 40 Hz to 1kHz, so that peaks from noise artifacts can be directly compared against peaks from the harmonics of the signal. The most predominant (non-signal) peak is an IMD product at 70Hz at -75dBrA, or 0.02%, between the signal and a power-supply noise peak. The highest signal harmonic is at 100Hz, at -90dBrA, or 0.0003%.

**Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, line-level input)**

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the output across an 8-ohm load at 10W for the analog line-level input. The input RMS values are set at -6.02dBrA so that, if summed for a mean frequency of 18.5kHz, would yield 10W (0dBrA) into 8 ohms at the output. We find that the second-order modulation product (*i.e.*, the difference signal of 1kHz) is at -100dBrA, or 0.001%, while the third-order modulation products, at 17kHz and 20kHz are just below -110dBrA, or 0.0003%.

**Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, coaxial digital input, 16/44.1)**

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the output across an 8-ohm load at 10W for the digital coaxial input at 16/44.1. We find that the second-order modulation product (*i.e.*, the difference signal of 1kHz) is at -100/-95dBrA, or 0.001/0.002%, while the third-order modulation products, at 17kHz and 20kHz, are at -85dBrA, or 0.006%.

**Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, coaxial digital input, 24/96)**

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the output across an 8-ohm load at 10W for the digital coaxial input at 24/96. We find that the second-order modulation product (*i.e.*, the difference signal of 1kHz) is at -100/-95dBrA, or 0.001/0.002%, while the third-order modulation products, at 17kHz and 20kHz, are at -85dBrA, or 0.006%.

**Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, MM phono input)**

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the output across an 8-ohm load at 10W for the MM phono input. We find that the second-order modulation product (*i.e.*, the difference signal of 1kHz) is at -95dBrA, or 0.002%, while the third-order modulation products, at 17kHz and 20kHz, are right around the -120dBrA noise floor.

**Square-wave response (10kHz)**

Above is the 10kHz squarewave response using the balanced analog line-level input, at roughly 10W into 8 ohms. Due to limitations inherent to the Audio Precision APx555 B Series analyzer, this graph should not be used to infer or extrapolate the RA-6000’s slew-rate performance. Rather, it should be seen as a qualitative representation of the RA-6000’s extended bandwidth. An ideal squarewave can be represented as the sum of a sinewave and an infinite series of its odd-order harmonics (*e.g.*, 10kHz + 30kHz + 50kHz + 70kHz . . .). A limited bandwidth will show only the sum of the lower-order harmonics, which may result in noticeable undershoot and/or overshoot, and softening of the edges. The RA-6000’s squarewave response is superb, showing only slight over/undershoot, or ringing near the sharp corners.

**Damping factor vs. frequency (20Hz to 20kHz)**

The final graph above is the damping factor as a function of frequency. For the left channel, we see a damping factor as high as 800 (20Hz), down to 630 from 30Hz to 4kHz, then down to 440 at 20kHz. For the right channel, we see a damping factor as high as 1000 (20Hz), down to 750 from 30Hz to 2kHz, then down to 400 at 20kHz. These are very high damping factors for an integrated amplifier.

*Diego Estan*

Electronics Measurement Specialist

- Details
- Parent Category: Products
- Category: Amplifier Measurements

Link: reviewed by Dennis Burger on *SoundStage! Access* on January 15, 2023

**General Information**

All measurements taken using an Audio Precision APx555 B Series analyzer.

The SVS Prime Wireless Pro Soundbase was conditioned for 1 hour at 1/8th full rated power (~9W into 8 ohms) before any measurements were taken. All measurements were taken with both channels driven, using a 120V/20A dedicated circuit, unless otherwise stated.

The Soundbase offers one RCA line-level analog input, RCA pre-amp outputs, one RCA sub-out (no bass management), one S/PDIF TosLink optical input, one HDMI input, one Bluetooth input, built-in streaming via ethernet or Wi-Fi, two pairs of speaker-level outputs, and one headphone output over a 1/8″ TRS connector. For the purposes of these measurements, the following inputs were evaluated: TosLink optical, RCA analog.

Most measurements were made with a 0.9Vrms line-level analog input and 0dBFS digital input. Our standard 2Vrms analog input needed to be reduced because of excessive distortion at the Soundbase’s input. The Soundbase digitizes incoming analog signals with an 88.2kHz sample rate, and even an analog signal at 1Vrms caused significant distortion. The signal-to-noise-ratio (SNR) measurements were made with the same input signal values, but with the volume set to achieve the 1% THD output power of 88W (8 ohms). For comparison, on the line-level input, a signal-to-noise-ratio measurement was also made with the volume at maximum, where only 0.517Vrms was required to achieve 88W into 8ohms.

The volume control does not offer a numerical display. Based on the high accuracy and repeatability of the left/right volume channel matching (see table below), the Soundbase volume control operates in the digital domain. The Soundbase offers 6dB to 2dB volume steps for the first five steps. Most of the volume range yields volume steps between 0.5dB and 1.5dB, randomly distributed across the range. Overall range is -34.4dB to +34.3dB (line-level input, speaker output).

Although the Soundbase uses a digital amplifier technology, a rise in the noise floor was only apparent at and above 100kHz or so, with the exception of the 88.2kHz sample-rate clock (see FFTs below). For this reason, our typical bandwidth filter setting of 10Hz-90kHz was maintained, with the exception of noise and THD+N measurements, where a 10Hz-80kHz was used, to ignore the 87.2kHz and 89.2kHz IMD peaks between the 1kHz signal and the 88.2kHz sample rate.

**Volume-control accuracy (measured at speaker outputs): left-right channel tracking**

Volume position | Channel deviation |

1 | 0.060dB |

20% | 0.061dB |

40% | 0.061dB |

60% | 0.060dB |

80% | 0.061dB |

Max | 0.061dB |

**Published specifications vs. our primary measurements**

The table below summarizes the measurements published by SVS for the Soundbase compared directly against our own. The published specifications are sourced from SVS’s website, either directly or from the manual available for download, or a combination thereof. With the exception of frequency response, where the Audio Precision bandwidth was extended to 500kHz, assume, unless otherwise stated, 10W into 8 ohms and a measurement input bandwidth of 10Hz to 80kHz, and the worst-case measured result between the left and right channels.

Parameter | Manufacturer | SoundStage! Lab |

Amplifier rated output power into 4 ohms (1% THD) | 150W | 151W |

Frequency response | 10Hz-20kHz (±1dB) | 10Hz-20kHz (-1.5,-0.4dB) |

Signal-to-noise ratio (full rated power, A-weighted) | 90dB | 101.2dB |

RCA input impedance | 20k ohms | 15.7k ohms |

RCA line-level and sub-out max output | 2Vrms | 4Vrms |

Headphone output max output (into 32 ohms) | 1Vrms | 0.9Vrms |

Our primary measurements revealed the following using the line-level analog input and digital optical input (unless specified, assume a 1kHz sine wave at 0.9Vrms or 0dBFS, 10W output, 8-ohm loading, 10Hz to 80kHz bandwidth):

Parameter | Left channel | Right channel |

Maximum output power into 8 ohms (1% THD+N, unweighted) | 88W | 88W |

Maximum output power into 4 ohms (1% THD+N, unweighted) | 151W | 151W |

Maximum burst output power (IHF, 8 ohms) | 95.6W | 95.6W |

Maximum burst output power (IHF, 4 ohms) | 166.9W | 166.9W |

Continuous dynamic power test (5 minutes, both channels driven) | passed | passed |

Crosstalk, one channel driven (10kHz) | -67.3dB | -66.7dB |

Damping factor | 131 | 99 |

Clipping no-load output voltage | 29.7Vrms | 29.7Vrms |

DC offset | <0.8mV | <0.5mV |

Gain (pre-out) | 12.6dB | 12.5dB |

Gain (maximum volume) | 34.3dB | 34.3dB |

IMD ratio (CCIF, 18kHz + 19kHz stimulus tones, 1:1) | <-73dB | <-75dB |

IMD ratio (SMPTE, 60Hz + 7kHz stimulus tones, 4:1 ) | <-74dB | <-78dB |

Input impedance (line input, RCA) | 15.8k ohms | 15.7k ohms |

Input sensitivity (for 1% THD, maximum volume) | 517mVrms | 518mVrms |

Noise level (A-weighted) | <0.75mVrms | <0.75mVrms |

Noise level (unweighted) | <1.9mVrms | <1.9mVrms |

Output impedance (pre-out) | 200 ohms | 201 ohms |

Signal-to-noise ratio (88W, A-weighted, 0.9Vrms in) | 101.2dB | 101.2dB |

Signal-to-noise ratio (88W, unweighted, 0.9Vrms in) | 93.4dB | 93.4dB |

Signal-to-noise ratio (88W, A-weighted, max volume) | 97.5dB | 97.8dB |

Dynamic range (full power, A-weighted, digital 24/96) | 102.2dB | 102.5dB |

Dynamic range (full power, A-weighted, digital 16/44.1) | 95.1dB | 95.1dB |

THD ratio (unweighted) | <0.005% | <0.005% |

THD ratio (unweighted, digital 24/96) | <0.004% | <0.005% |

THD ratio (unweighted, digital 16/44.1) | <0.004% | <0.005% |

THD+N ratio (A-weighted) | <0.01% | <0.01% |

THD+N ratio (A-weighted, digital 24/96) | <0.01% | <0.01% |

THD+N ratio (A-weighted, digital 16/44.1) | <0.01% | <0.01% |

THD+N ratio (unweighted) | <0.023% | <0.023% |

Minimum observed line AC voltage | 124VAC | 124VAC |

For the continuous dynamic power test, the Soundbase was able to sustain 148W into 4 ohms (~1.5% THD) using an 80Hz tone for 500ms, alternating with a signal at -10dB of the peak (14.8W) for 5 seconds, for 5 continuous minutes without inducing a fault or the initiation of a protective circuit. This test is meant to simulate sporadic dynamic bass peaks in music and movies. During the test, the top of the Soundbase was only slightly warm to the touch.

Our primary measurements revealed the following using the analog input at the headphone output (unless specified, assume a 1kHz sine wave, 0.9Vrms output, 300 ohms loading, 10Hz to 80kHz bandwidth):

Parameter | Left channel | Right channel |

Maximum output power into 600 ohms (1% THD+N, unweighted) | 37mW | 37mW |

Maximum output power into 300 ohms (1% THD+N, unweighted) | 73mW | 73mW |

Maximum output power into 32 ohms (1% THD+N, unweighted) | 24mW | 24mW |

Gain | 18.5dB | 18.5dB |

Output impedance | 96 ohms | 96 ohms |

Noise level (A-weighted) | <20uVrms | <20uVrms |

Noise level (unweighted) | <90uVrms | <90uVrms |

Signal-to-noise ratio (A-weighted, ref. max output voltage) | 102.4dB | 102.6dB |

Signal-to-noise ratio (unweighted, ref. max output voltage) | 93.3dB | 93.3dB |

THD ratio (unweighted) | <0.0026% | <0.0028% |

THD+N ratio (A-weighted) | <0.0032% | <0.0034% |

THD+N ratio (unweighted) | <0.0053% | <0.0053% |

**Frequency response (8-ohm loading, line-level input)**

In our frequency-response plots above, measured across the speaker outputs at 10W into 8 ohms, the Soundbase is within 0.5dB of flat in the audioband (20Hz to 20kHz). The Soundbase is -1.5dB at 10Hz and -0.4dB at 20kHz, not quite corroborating SVS’s claim of 10Hz-20kHz (±1dB), but it’s very close. There is also a brickwall-type attenuation behavior around 44kHz, indicating that the Soundbase is digitizing incoming analog signals with a 88.2kHz sample rate (further evidence of this is provided in the FFTs below). In the graph above and most of the graphs below, only a single trace may be visible. This is because the left channel (blue or purple trace) is performing identically to the right channel (red or green trace), and so they perfectly overlap, indicating that the two channels are ideally matched.

**Phase response (8-ohm loading, line-level input)**

Above are the phase response plots from 20Hz to 20kHz for the line-level input, measured across the speaker outputs at 10W into 8 ohms. The Soundbase does not invert polarity and exhibits, at worst, 40 degrees of phase shift (at 20kHz) within the audioband.

**Frequency response vs. input type (analog and 16/44.1, 24/96, and 24/192 inputs with 8-ohm loading, left channel only)**

The chart above shows the Soundbase’s frequency response as a function of input type measured across the speaker outputs at 10W into 8 ohms. The green trace is the same analog input data from the previous graph. The blue trace is for a 16-bit/44.1kHz dithered digital input signal from 5Hz to 22kHz using the optical input, and the purple trace is for a 24/96 dithered digital input signal from 5Hz to 48kHz, while the pink trace is for a 24/192 dithered digital input signal from 5Hz to 96kHz. It appears that the Soundbase’s optical input resamples all incoming digital data at 44.1kHz, which is why all three digital input frequency response curves perfectly overlap and look as one. The -3dB point for the optical input is at 20.9kHz, with brickwall-type attenuation.

**Digital linearity (16/44.1 and 24/96 data)**

The chart above shows the results of a linearity test for the optical digital input for both 16/44.1 (blue/red) and 24/96 (purple/green) input data, measured at the line level output of the Soundbase. The digital input is swept with a dithered 1kHz input signal from -120dBFS to 0dBFS, and the output is analyzed by the APx555. The ideal response would be a straight flat line at 0dB. Both data were essentially perfect as of -105dBFS down to 0dBFS. At -120dBFS, all data are roughly +6dB above reference.

**Impulse response (24/44.1 data)**

The graph above shows the impulse response for the Soundbase, fed to the optical digital input, measured at the line-level output, for a looped 24/44.1 test file that moves from digital silence to full 0dBFS (all “1”s) for one sample period, then back to digital silence. We find a non-symmetrical response with no pre-ringing but significant post-ringing.

**J-Test (optical input)**

The chart above shows the results of the J-Test test for the coaxial digital input measured at the line level output of the Soundbase. J-Test was developed by Julian Dunn the 1990s. It is a test signal: specifically, a -3dBFS undithered 12kHz squarewave sampled (in this case) at 48kHz (24 bits). Since even the first odd harmonic (*i.e.*, 36kHz) of the 12kHz squarewave is removed by the bandwidth limitation of the sampling rate, we are left with a 12kHz sine wave (the main peak). In addition, an undithered 250Hz squarewave at -144dBFS is mixed with the signal. This test file causes the 22 least significant bits to constantly toggle, which produces strong jitter spectral components at the 250Hz rate and its odd harmonics. The test file shows how susceptible the DAC and delivery interface are to jitter, which would manifest as peaks above the noise floor at 500Hz intervals (*e.g.*, 250Hz, 750Hz, 1250Hz, etc.). Note that the alternating peaks are in the test file itself, but at levels of -144dBrA and below. The test file can also be used in conjunction with artificially injected sine-wave jitter by the Audio Precision, to show how well the DAC rejects jitter.

The optical input exhibits low-level peaks at low frequencies, at -100dBrA and below. This is a good J-Test result, indicating that Soundbase DAC should yield good jitter immunity.

**J-Test with 100ns of injected jitter (optical input)**

The optical input was also tested for jitter immunity by injecting artificial sine-wave jitter at 2kHz, which would manifest as sidebands at 10kHz and 14kHz without any jitter rejection. Jitter immunity proved exceptional, with no visible sidebands at the 100ns jitter level.

**J-Test with 500ns of injected jitter (optical input)**

The optical input was also tested for jitter immunity by injecting artificial jitter sine-wave jitter at 2kHz, which would manifest as sidebands at 10kHz and 14kHz without any jitter rejection. Jitter immunity proved exceptional, with no visible sidebands at a very high 500ns of injected jitter. Above this level of jitter, the Soundbase DAC lost sync with the signal.

**Wideband FFT spectrum of white noise and 19.1kHz sine-wave tone (coaxial input)**

The chart above shows a fast Fourier transform (FFT) of the Soundbase’s line-level output with white noise at -4dBFS (blue/red) and a 19.1 kHz sinewave at 0dBFS fed to the optical digital input, sampled at 16/44.1. The steep roll-off around 20kHz in the white-noise spectrum shows the behavior of the Soundbase’s reconstruction filter. There are no aliased image peaks within the audioband. The primary aliasing signal at 25kHz is at -100dBrA, while the second and third distortion harmonics (38.2, 57.3kHz) of the 19.1kHz tone are at -115 and -85dBrA.

**RMS level vs. frequency vs. load impedance (1W, left channel only)**

The chart above shows RMS level (relative to 0dBrA, which is 1W into 8 ohms, or 2.83Vrms) as a function of frequency, for the analog line-level input swept from 5Hz to 100kHz. The blue plot is into an 8-ohm load, the purple is into a 4-ohm load, the pink plot is an actual speaker (Focal Chora 806, measurements can be found here), and the cyan plot is no load connected. The chart below . . .

. . . is the same but zoomed in to highlight differences. Here we find the deviations between no load and 4 ohms to be almost 0.2dB, which is an indication of a mid-level damping factor, or fairly low output impedance. When a real speaker is used, deviations are within about 0.15dB.

**THD ratio (unweighted) vs. frequency vs. output power**

The chart above shows THD ratios at the output into 8 ohms as a function of frequency for a sine-wave stimulus at the analog line-level input. The blue and red plots are for left and right channels at 1W output into 8 ohms, purple/green at 10W, and pink/orange at 60W. The power was varied using the volume control. At 1W, THD ratios ranged from 0.1% at 20Hz, down to 0.004-0.005% between 200Hz and 5kHz, then up to 0.01% at 20kHz. At 10W, THD ratios ranged from 0.05% at 20Hz, down to 0.004-0.005% between 200Hz and 2kHz, then up to 0.02% at 20kHz. At 60W, THD ratios ranged from 0.2% at 20Hz, then a slow decrease down to 0.03% at 20kHz.

**THD ratio (unweighted) vs. output power at 1kHz into 4 and 8 ohms**

The chart above shows THD ratios measured at the output of the Soundbase as a function of output power for the analog line-level input for an 8-ohm load (blue/red for left/right channels) and a 4-ohm load (purple/green for left/right channels). THD ratios were lower into 8 ohms (compared to 4 ohms) at around 0.003-0.004% from 50mW up to 10W, then a steady rise up to the 1% THD value at 88W. THD ratios into 4 ohms ranged from 0.005% at 50mW up to 0.01-0.02% between 3W and the “knee” at 100W, then up to the 1% mark at 151W.

**THD+N ratio (unweighted) vs. output power at 1kHz into 4 and 8 ohms**

The chart above shows THD+N ratios measured at the output of the Soundbase as a function of output power for the analog line level-input, for an 8-ohm load (blue/red for left/right channels) and a 4-ohm load (purple/green for left/right channels). Overall, THD+N values for both loads were similar up to 50W, ranging from 0.05% to 0.02%.

**THD ratio (unweighted) vs. frequency at 8, 4, and 2 ohms (left channel only)**

The chart above shows THD ratios measured at the output of the Soundbase as a function of frequency into three different loads (8/4/2 ohms) for a constant input voltage that yields 10W at the output into 8 ohms (and roughly 20W into 4 ohms, and 40W into 2 ohms) for the analog line-level input. The 8-ohm load is the blue trace, the 4-ohm load the purple trace, and the 2-ohm load the pink trace. We find similar THD values of roughly 0.05% at low (20-50Hz) and high (5-20kHz) frequencies across all three loads. Between 200Hz and 3kHz, the 8-ohm data (at 0.005%) is roughly 10dB lower than the 4-ohm data, which, in turn, is roughly 5dB lower than the 2-ohm data. This is a very good result for such a small, affordable integrated amp, and shows good stability even into 2-ohm loads.

**THD ratio (unweighted) vs. frequency into 8 ohms and real speakers (left channel only)**

The chart above shows THD ratios measured at the output of the Soundbase as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). All THD data are roughly the same across all three loads. Starting at 0.1% at 20Hz, down to nearly 0.003% from 200Hz to 3kHz, then up to 0.01% at 20kHz (nearly 0.02% for the three-way speaker). This is another strong result, showing how the Soundbase will yield consistent THD results for different real-world loads.

**IMD ratio (CCIF) vs. frequency into 8 ohms and real speakers (left channel only)**

The chart above shows intermodulation distortion (IMD) ratios measured at the output of the Soundbase as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. Here the CCIF IMD method is used, where the primary frequency is swept from 20kHz (F1) down to 2.5kHz, and the secondary frequency (F2) is always 1kHz lower than the primary, with a 1:1 ratio. The CCIF IMD analysis results are the sum of the second (F1-F2 or 1kHz) and third modulation products (F1+1kHz, F2-1kHz). The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). At high frequencies (10-20kHz), there is roughly a 5dB differences in IMD values between both the dummy load and two-way speaker (-90 to -85dB) and the three-way speaker (-85 to -80dB). Otherwise, all three plots are very similar below 7-8kHz, at -90 to -85dB, or 0.003 to 0.005%.

**IMD ratio (SMPTE) vs. frequency into 8 ohms and real speakers (left channel only)**

The chart above shows IMD ratios measured at the output of the Soundbase as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. Here, the SMPTE IMD method is used, where the primary frequency (F1) is swept from 250Hz down to 40Hz, and the secondary frequency (F2) is held at 7kHz with a 4:1 ratio. The SMPTE IMD analysis results consider the second (F2 ± F1) through the fifth (F2 ± 4xF1) modulation products. The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). All three plots yielded roughly the same IMD values, between 0.02% to 0.03% up to 500Hz, then a drop to 0.01%.

**FFT spectrum – 1kHz (line-level input)**

Shown above is the fast Fourier transform (FFT) for a 1kHz input sine-wave stimulus, measured at the output across an 8-ohm load at 10W for the analog line-level input. We see that the signal’s second harmonic, at 2kHz, is at -90/-100dBrA (left/right), or 0.003/0.001%, while the odd harmonics at 3 and 5kHz are at -65dBrA, or 0.002%. There are low level power-supply-related noise peaks at the fundamental (60Hz) at -105dBRa, or 0.0006%, and the third (180Hz), fifth (300Hz) and seventh (420Hz) harmonics at -110dBrA, or 0.0003%, and below. The peaks seen at high frequencies at 87.2kHz and 89.2kHz are the IMD results between the signal (1kHz) and the sampling frequency of 88.2kHz. This is more evidence that analog signals are digitized at 88.2kHz.

**FFT spectrum – 1kHz (digital input, 16/44.1 data at 0dBFS)**

Shown above is the fast Fourier transform (FFT) for a 1kHz input sine-wave stimulus, measured at the output across an 8-ohm load at 10W for the optical digital input, sampled at 16/44.1. Signal harmonics are very similar to the analog input FFT above, except for the left channel’s second signal harmonic (2kHz), which is 5dB lower here, and the right channel’s third signal harmonic (3kHz), which is 5dB higher here. Power-supply-related noise peaks are barely visible here, and are below -110dBrA, or 0.0006%.

**FFT spectrum – 1kHz (digital input, 24/96 data at 0dBFS)**

Shown above is the fast Fourier transform (FFT) for a 1kHz input sine-wave stimulus, measured at the output across an 8-ohm load at 10W for the optical digital input, sampled at 24/96. The FFT is essentially identical to 16/44.1 FFT above.

**FFT spectrum – 1kHz (digital input, 16/44.1 data at -90dBFS)**

Shown above is the FFT for a 1kHz -90dBFS dithered 16/44.1 input sine-wave stimulus at the optical digital input, measured at the output across an 8-ohm load. We see the 1kHz primary signal peak, at the correct amplitude, and extremely low level power-supply related peaks below -130dBrA.

**FFT spectrum – 1kHz (digital input, 24/96 data at -90dBFS)**

Shown above is the FFT for a 1kHz -90dBFS dithered 24/96 input sine-wave stimulus at the optical digital input, measured at the output across an 8-ohm load. We see the 1kHz primary signal peak, at the correct amplitude, and extremely low level power supply-related peaks below -130dBrA.

**FFT spectrum – 50Hz (line-level input)**

Shown above is the FFT for a 50Hz input sine-wave stimulus measured at the output across an 8-ohm load at 10W for the analog line-level input. The X axis is zoomed in from 40Hz to 1kHz, so that peaks from noise artifacts can be directly compared against peaks from the harmonics of the signal. The most significant non-signal peaks are from the signal’s second (100Hz) and third (150Hz) harmonics, at -80dBrA, or 0.01%, and -75dBrA, or 0.02%, respectively. Power-supply noise-related harmonics can be seen at the fundamental (60Hz), at -105dBrA, or 0.0006%, and higher-order harmonics and IMD products can be seen at and below -110dBrA, or 0.0003%.

**Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, line-level input)**

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sine-wave stimulus tone measured at the output across an 8-ohm load at 10W for the analog line-level input. The input RMS values are set at -6.02dBrA so that, if summed for a mean frequency of 18.5kHz, would yield 10W (0dBrA) into 8 ohms at the output. We find that the second-order modulation product (*i.e.*, the difference signal of 1kHz) is at -100/-110dBRa (left/right), or 0.001/0.0003%, while the third-order modulation products, at 17kHz and 20kHz, are just above -90dBrA, or 0.003%.

**Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, optical digital input, 16/44.1)**

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sine-wave stimulus tone measured at the output across an 8-ohm load at 10W for the digital optical input at 16/44.1. We find that the second-order modulation product (*i.e.*, the difference signal of 1kHz) is at -110/-100dBRa (left/right), or 0.0003/0.001%, while the third-order modulation products, at 17kHz and 20kHz, are just above -90dBrA, or 0.003%.

**Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, optical digital input, 24/96)**

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sine-wave stimulus tone measured at the output across an 8-ohm load at 10W for the digital optical input at 24/96. We find that the second-order modulation product (*i.e.*, the difference signal of 1kHz) is at -110/-100dBRa (left/right), or 0.0003/0.001%, while the third-order modulation products, at 17kHz and 20kHz, are just above -90dBrA, or 0.003%.

**Squarewave response (10kHz)**

Above is the 10kHz squarewave response using the analog line-level input, at roughly 10W into 8 ohms. Due to limitations inherent to the Audio Precision APx555 B Series analyzer, this graph should not be used to infer or extrapolate the Soundbase’s slew-rate performance. Rather, it should be seen as a qualitative representation of the Soundbase’s limited bandwidth. An ideal squarewave can be represented as the sum of a sine wave and an infinite series of its odd-order harmonics (*e.g.*, 10kHz + 30kHz + 50kHz + 70kHz . . .). A limited bandwidth will show only the sum of the lower-order harmonics, which may result in noticeable undershoot and/or overshoot, and softening of the edges. In this case, because of the digital nature of the amplifier, we see a 400kHz switching frequency (see 1MHz FFT below) riding on top of the squarewave.

**Squarewave response (10kHz, restricted 250kHz bandwidth)**

Above is the same 10kHz squarewave response using the analog line-level input, at roughly 10W into 8 ohms, this time with a 250kHz input bandwidth on the analyzer to filter out the 400kHz switching frequency. We can see significant over/undershoot and softening in the corners of the squarewave, a consequence of the Soundbase’s limited bandwidth, which is capped at half the sampling frequency (88.2kHz) used to digitize the incoming analog signals.

**FFT spectrum (1MHz bandwidth)**

Shown above is the fast Fourier transform (FFT) for a 1kHz input sine-wave stimulus, measured at the output across an 8-ohm load at 10W for the analog line-level input, with an extended 1MHz input bandwidth. This enables us to see the high-frequency noise above 100kHz reaching almost -90dBrA at 200kHz. We also see a clear peak at 400kHz, reaching -50dBrA, and its harmonics (800kHz, 1.2MHz). These peaks, as well as the noise, are a result of the digital amplifier technology used in the Soundbase; however, they are far above the audioband—and therefore inaudible—and so high in frequency that any loudspeaker the amplifier is driving should filter it all out anyway.

**Damping factor vs. frequency (20Hz to 20kHz)**

The final graph above is the damping factor as a function of frequency. We can see the left channel outperforming the right channel, with values ranging from 155 at 20Hz down to 90 at 20kHz. The right channel ranged from 112 at 20Hz down to 72 at 20kHz. These are good damping factor results for digital-amplifier-type technology, and do not show significant reductions in damping factor at high frequencies, which can be the case with other digital amplifiers.

*Diego Estan*

Electronics Measurement Specialist

- Details
- Parent Category: Products
- Category: Amplifier Measurements

Link: reviewed by Dennis Burger on *SoundStage! Access* on December 1, 2022

**General Information**

All measurements taken using an Audio Precision APx555 B Series analyzer.

The Technics SU-RG700M2 was conditioned for 1 hour at 1/8th full rated power (~9W into 8 ohms) before any measurements were taken. All measurements were taken with both channels driven, using a 120V/20A dedicated circuit, unless otherwise stated.

The SU-RG700M2 offers two line-level analog inputs (RCA); one pair of phono RCA inputs, configurable for moving-magnet (MM) or moving-coil (MC) operation, RCA pre-amp outputs, RCA main-in inputs, two coaxial (RCA) and two optical (TosLink) S/PDIF inputs, one USB digital input, two pair of speaker-level outputs, and one headphone output over a 1/4″ TRS connector. For the purposes of these measurements, the following inputs were evaluated: digital coaxial, analog line-level, as well as phono (MM and MC). Unless otherwise stated, Direct In mode was used with Attenuation and LAPC both off.

Most measurements were made with a 2Vrms line-level analog input, 5mVrms MM input, 0.5mVrms MC input, and 0dBFS digital input. The volume control is variable from -88dB to 0dB. The following volume settings yielded approximately 10W into 8 ohms: -29dB for analog line-level and digital, -14dB for MM and MC. The signal-to-noise ratio (SNR) measurements were made with the same input signal values but with the volume set to achieve the rated output power of 70W (8 ohms). For comparison, on the line-level input, a SNR measurement was also made with the volume at maximum, where only 0.188Vrms was required to achieve 70W into 8ohms.

Based on the accuracy and repeatability of the left/right volume channel matching (see table below), the SU-RG700M2 volume control operates in the digital domain. The SU-RG700M2 offers 5dB volume steps ranging from -88dB to -78dB, 4dB steps from -78dB to -70dB, 3dB steps from -70dB to -64dB, 2dB steps from -64dB to -56dB, 1dB steps from -56dB to -19dB, and 0.5dB steps from -19dB to 0dB. Overall range is -45.7dB to +42dB (line-level input, speaker output).

Because the SU-RG700M2 is a digital amplifier technology that exhibits considerable noise above 20kHz (see FFTs below), our typical input bandwidth filter setting of 10Hz-90kHz was necessarily changed to 10Hz-22.4kHz for all measurements, except for frequency response and for FFTs. In addition, THD versus frequency sweeps were limited to 6kHz to adequately capture the second and third signal harmonics with the restricted-bandwidth setting.

**Volume-control accuracy (measured at speaker outputs): left-right channel tracking**

Volume position | Channel deviation |

-88dB | 0.018dB |

-60dB | 0.055dB |

-50dB | 0.055dB |

-30dB | 0.057dB |

-20dB | 0.056dB |

-10dB | 0.057dB |

0dB | 0.058dB |

**Published specifications vs. our primary measurements**

The table below summarizes the measurements published by Technics for the SU-RG700M2 compared directly against our own. The published specifications are sourced from Technics’ website, either directly or from the manual available for download, or a combination thereof. With the exception of frequency response, where the Audio Precision bandwidth was extended to 250kHz, assume, unless otherwise stated, 10W into 8 ohms and a measurement input bandwidth of 10Hz to 22.4kHz, and the worst-case measured result between the left and right channels.

Parameter | Manufacturer | SoundStage! Lab |

Amplifier rated output power into 8 ohms (0.5% THD) | 70W | 81W |

Amplifier rated output power into 4 ohms (0.5% THD) | 140W | 152W |

Frequency response (analog line-level in, speaker out 8 ohms) | 5Hz-80kHz (-3dB) | 5Hz-80kHz (-1dB) |

Frequency response (digital in, 24/192, speaker out 8 ohms) | 5Hz-80kHz (-3dB) | 5Hz-80kHz (-0.4dB) |

Frequency response (phono MM, speaker out 8 ohms) | RIAA 20Hz-20kHz (±1dB) | RIAA 20Hz-20kHz (±0.5dB) |

Frequency response (phono MC, speaker out 8 ohms) | RIAA 20Hz-20kHz (±1dB) | RIAA 20Hz-20kHz (±1dB) |

Input sensitivity (analog line-level in) | 200mVrms | 188mVrms |

Input impedance (analog line-level in) | 22k ohms | 37.4k ohms |

Input sensitivity (phono MM) | 2.5mVrms | 2.85mVrms |

Input impedance (phono MM) | 47k ohms | 44.7k ohms |

Input sensitivity (phono MC) | 0.3mVrms | 0.25mVrms |

Input impedance (phono MC) | 100 ohms | 146 ohms |

Our primary measurements revealed the following using the line-level analog input and digital coaxial input (unless specified, assume a 1kHz sine wave at 2Vrms or 0dBFS, 10W output, 8-ohm loading, 10Hz to 22.4kHz bandwidth):

Parameter | Left channel | Right channel |

Maximum output power into 8 ohms (1% THD+N, unweighted) | 85W | 85W |

Maximum output power into 4 ohms (1% THD+N, unweighted) | 156W | 156W |

Maximum burst output power (IHF, 8 ohms) | 85W | 85W |

Maximum burst output power (IHF, 4 ohms) | 156W | 156W |

Continuous dynamic power test (5 minutes, both channels driven) | passed | passed |

Crosstalk, one channel driven (10kHz) | -73.6dB | -77.2dB |

Damping factor | 31.7 | 30.8 |

Clipping no-load output voltage | 27Vrms | 27Vrms |

DC offset | <-17mV | <20mV |

Gain (pre-out) | 15.3dB | 15.2dB |

Gain (maximum volume) | 42.04dB | 41.97dB |

IMD ratio (CCIF, 18kHz + 19kHz stimulus tones, 1:1) | <-60.5dB | <-64.3dB |

IMD ratio (SMPTE, 60Hz + 7kHz stimulus tones, 4:1 ) | <-51.3dB | <-53.2dB |

Input impedance (line input, RCA) | 37.4k ohms | 37.9k ohms |

Input sensitivity (for rated power, maximum volume) | 188mVrms | 188mVrms |

Noise level (A-weighted) | <1.26mVrms | <1.15mVrms |

Noise level (unweighted) | <1.72mVrms | <1.62mVrms |

Output impedance (pre-out) | 723 ohms | 723 ohms |

Signal-to-noise ratio (full power, A-weighted, 2Vrms in) | 104.4dB | 105.0dB |

Signal-to-noise ratio (full power, unweighted, 2Vrms in) | 101.5dB | 102.0dB |

Signal-to-noise ratio (full power, A-weighted, max volume) | 86.3dB | 86.0dB |

Dynamic range (full power, A-weighted, digital 24/96) | 109.4dB | 111.8dB |

Dynamic range (full power, A-weighted, digital 16/44.1) | 95.8dB | 95.8dB |

THD ratio (unweighted) | <0.057% | <0.063% |

THD ratio (unweighted, digital 24/96) | <0.059% | <0.064% |

THD ratio (unweighted, digital 16/44.1) | <0.060% | <0.064% |

THD+N ratio (A-weighted) | <0.064% | <0.071% |

THD+N ratio (A-weighted, digital 24/96) | <0.066% | <0.072% |

THD+N ratio (A-weighted, digital 16/44.1) | <0.067% | <0.073% |

THD+N ratio (unweighted) | <0.060% | <0.065% |

Minimum observed line AC voltage | 123VAC | 123VAC |

For the continuous dynamic power test, the SU-G700M2 was able to sustain 164W into 4 ohms (~4% THD) using an 80Hz tone for 500ms, alternating with a signal at -10dB of the peak (16.4W) for 5 seconds, for 5 continuous minutes without inducing a fault or the initiation of a protective circuit. This test is meant to simulate sporadic dynamic bass peaks in music and movies. During the test, the top of the SU-G700M2 was only slightly warm to the touch.

Our primary measurements revealed the following using the phono-level input, MM configuration (unless specified, assume a 1kHz 5mVrms sine-wave input, 10W output, 8-ohm loading, 10Hz to 22.4kHz bandwidth):

Parameter | Left channel | Right channel |

Crosstalk, one channel driven (10kHz) | -63.4dB | -64.8dB |

DC offset | <-1.6mV | <-1.8mV |

Gain (default phono preamplifier) | 42.4dB | 42.4dB |

IMD ratio (CCIF, 18kHz + 19kHz stimulus tones, 1:1) | <-59.1dB | <-62.2dB |

IMD ratio (CCIF, 3kHz + 4kHz stimulus tones, 1:1) | <-60.2dB | <-62.2dB |

Input impedance | 45.9k ohms | 44.7k ohms |

Input sensitivity (to max power with max volume) | 2.85mVrms | 2.85mVrms |

Noise level (A-weighted) | <1.3mVrms | <1.2mVrms |

Noise level (unweighted) | <1.9mVrms | <1.8mVrms |

Overload margin (relative 5mVrms input, 1kHz) | 19.8dB | 19.9dB |

Signal-to-noise ratio (full rated power, A-weighted) | 88.2dB | 88.1dB |

Signal-to-noise ratio (full rated power, unweighted) | 80.9dB | 80.6dB |

THD (unweighted) | <0.064% | <0.065% |

THD+N (A-weighted) | <0.073% | <0.074% |

THD+N (unweighted) | <0.068% | <0.069% |

Our primary measurements revealed the following using the phono-level input, MC configuration (unless specified, assume a 1kHz 0.5mVrms sine-wave input, 10W output, 8-ohm loading, 10Hz to 22.4kHz bandwidth):

Parameter | Left channel | Right channel |

Crosstalk, one channel driven (10kHz) | -47.8dB | -50.1dB |

DC offset | <-8mV | <-1mV |

Gain (default phono preamplifier) | 63.4dB | 63.4dB |

IMD ratio (CCIF, 18kHz + 19kHz stimulus tones, 1:1) | <-59dB | <-62dB |

IMD ratio (CCIF, 3kHz + 4kHz stimulus tones, 1:1) | <-60dB | <-63dB |

Input impedance | 146 ohms | 146 ohms |

Input sensitivity (to max power with max volume) | 250uVrms | 250uVrms |

Noise level (A-weighted) | <2mVrms | <2mVrms |

Noise level (unweighted) | <9mVrms | <9mVrms |

Overload margin (relative 0.5mVrms input, 1kHz) | 18.9dB | 18.9dB |

Signal-to-noise ratio (full rated power, A-weighted) | 73.6dB | 73.3dB |

Signal-to-noise ratio (full rated power, unweighted) | 62.3dB | 60.9dB |

THD (unweighted) | <0.071% | <0.069% |

THD+N (A-weighted) | <0.083% | <0.081% |

THD+N (unweighted) | <0.12% | <0.13% |

Our primary measurements revealed the following using the analog input at the headphone output (unless specified, assume a 1kHz sine wave, 2Vrms output, 300 ohms loading, 10Hz to 22.4kHz bandwidth):

Parameter | Left channel | Right channel |

Maximum output power into 600 ohms (1% THD+N, unweighted) | 27mW | 27mW |

Maximum output power into 300 ohms (1% THD+N, unweighted) | 45mW | 45mW |

Maximum output power into 32 ohms (1% THD+N, unweighted) | 61mW | 61mW |

Gain | 26.7dB | 26.6dB |

Output impedance | 67.4 ohms | 67.3 ohms |

Noise level (A-weighted) | <21uVrms | <22uVrms |

Noise level (unweighted) | <29uVrms | <32uVrms |

Signal-to-noise (A-weighted, ref. max output voltage) | 103.6dB | 103.7dB |

Signal-to-noise (unweighted, ref. max output voltage) | 100.9dB | 100.8dB |

THD ratio (unweighted) | <0.0090% | <0.0058% |

THD+N ratio (A-weighted) | <0.010% | <0.0065% |

THD+N ratio (unweighted) | <0.0091% | <0.0061% |

**Frequency response (8-ohm loading, line-level input)**

In our frequency response plots above, measured across the speaker outputs at 10W into 8 ohms, the SU-G700M2 is nearly flat within the audioband (20Hz to 20kHz). The SU-G700M2 is -0.2dB at 20Hz and +0.1dB at 20kHz. At the extremes, we are at -3.5dB at 5Hz and -1dB at 80kHz. These data essentially corroborate Technics’ claim of 5Hz to 80kHz (-3dB). There’s a rise in the frequency response above 20kHz, where we see +0.5dB at 50kHz, which is a result of the digital amplifier and its high output impedance at high frequencies. Into a 4-ohm load (see RMS level vs. frequency vs load impedance graph below), instead of a rise there is a significant dip at and above 20kHz. In the graph above and most of the graphs below, only a single trace may be visible. This is because the left channel (blue or purple trace) is performing identically to the right channel (red or green trace), and so they perfectly overlap, indicating that the two channels are ideally matched.

**Frequency response (8-ohm loading, line-level input, bass and treble controls)**

Above is a frequency-response plot measured at the speaker-level outputs into 8 ohms, with the bass and treble controls set to maximum (blue/red plots) and minimum (purple/green plots). We see that for the bass and treble controls, roughly +/-7dB of gain/cut is available.

**Frequency response (8-ohm loading, line-level input, midrange control)**

Above is a frequency response plot measured at the speaker-level outputs into 8 ohms, with the midrange control set to maximum (blue/red plots) and minimum (purple/green plots). We see that there is roughly +/-8dB of gain/cut available centered around 1kHz.

**Frequency response (8-ohm loading, line-level input, bass and treble and midrange controls)**

Above is a frequency-response plot measured at the speaker-level outputs into 8 ohms, with the bass, treble, and midrange controls set to maximum (blue/red plots) and minimum (purple/green plots). The levels are relative to 3kHz. We see that with all controls set to either minimum or maximum, there is a maximum deviation of no more than +/-5dB. When all the tone controls are at their maximum, there are two dips in the frequency response at roughly 300Hz and 3kHz. When the tone controls are at their minimum, we see troughs at 300Hz and 3kHz.

**Phase response (8-ohm loading, line-level input)**

Above are the phase-response plots from 20Hz to 20kHz for the line-level input, measured across the speaker outputs at 10W into 8 ohms. The SU-G700M2 does not invert polarity and exhibits, at worst, 40 degrees (at 20kHz) of phase shift within the audioband.

**Frequency response vs. input type (8-ohm loading, left channel only)**

The chart above shows the SU-G700M2’s frequency response as a function of input type measured across the speaker outputs at 10W into 8 ohms. The green trace is the same analog input data from the previous graph. The blue trace is for a 16-bit/44.1kHz dithered digital input signal from 5Hz to 22kHz using the coaxial input, and the purple trace is for a 24/96 dithered digital input signal from 5Hz to 48kHz, while the pink trace is for a 24/192 dithered digital input signal from 5Hz to 96kHz. The 16/44.1 data exhibits brickwall-type filtering, with a -3dB point at 21.1kHz. The 24/96 and 24/192 kHz data yielded -3dB points at 46.5kHz and 91.9kHz respectively. The analog data looks nearly identical to the 24/192 digital data, which is evidence for the SU-G700M2 sampling incoming analog signals at 192kHz.

**Frequency response (8-ohm loading, MM phono input)**

The chart above shows the frequency response for the phono input (MM configuration) without (blue/red) and with (purple/green) the subsonic filter enabled. What is shown is the deviation from the RIAA curve, where the input signal sweep is EQ’d with an inverted RIAA curve supplied by Audio Precision (*i.e.*, zero deviation would yield a flat line at 0dB). We see a maximum deviation of about +0.2/-0.5dB (30Hz/10kHz) from 20Hz to 20kHz. With the subsonic filter engaged, we find the -3dB point at 24Hz.

**Frequency response (8-ohm loading, MC phono input)**

The chart above shows the frequency response for the phono input (MC configuration) without (blue/red) and with (purple/green) the subsonic filter enabled. What is shown is the deviation from the RIAA curve, where the input signal sweep is EQ’d with an inverted RIAA curve supplied by Audio Precision (*i.e.*, zero deviation would yield a flat line at 0dB). We see a maximum deviation of about +0.2/-1dB (30Hz/20kHz) from 20Hz to 20kHz. With the subsonic filter engaged, we find the -3dB point at 24Hz.

**Phase response (MM input)**

Above is the phase response plot from 20Hz to 20kHz for the phono input (MM configuration), measured across the speaker outputs at 10W into 8 ohms. The SU-G700M2 does not invert polarity. For the phono input, since the RIAA equalization curve must be implemented, which ranges from +19.9dB (20Hz) to -32.6dB (90kHz), phase shift at the output is inevitable. Here we find a worst case of about -60 degrees at 200Hz and 5kHz.

**Phase response (MC input)**

Above is the phase response plot from 20Hz to 20kHz for the phono input (MC configuration), measured across the speaker outputs at 10W into 8 ohms. The SU-G700M2 does not invert polarity. Here we find a worst case of about -60 degrees at 200Hz and 5kHz.

**Digital linearity (16/44.1 and 24/96 data)**

The chart above shows the results of a linearity test for the coaxial digital input for both 16/44.1 (blue/red) and 24/96 (purple/green) input data, measured at the line level output of the SU-G700M2. The digital input is swept with a dithered 1kHz input signal from -120dBFS to 0dBFS, and the output is analyzed by the APx555. The ideal response would be a straight flat line at 0dB. Both data were essentially perfect as of -90dBFS down to 0dBFS. At -120dBFS, the 16/44.1 data were about 7dB above reference, while the 24/96 data were at +6dBFS. This is a mediocre linearity test result.

**Impulse response (24/44.1 data)**

The graph above shows the impulse response for the SU-G700M2, fed to the coaxial digital input, measured at the line level output, for a looped 24/44.1 test file that moves from digital silence to full 0dBFS (all “1”s), for one sample period then back to digital silence. We find a typical, symmetrical sinc function reconstruction filter.

**J-Test (coaxial)**

The chart above shows the results of the J-Test test for the coaxial digital input measured at the line level output of the SU-G700M2. J-Test was developed by Julian Dunn the 1990s. It is a test signal—specifically, a -3dBFS undithered 12kHz squarewave sampled (in this case) at 48kHz (24 bits). Since even the first odd harmonic (*i.e.*, 36kHz) of the 12kHz squarewave is removed by the bandwidth limitation of the sampling rate, we are left with a 12kHz sine wave (the main peak). In addition, an undithered 250Hz squarewave at -144dBFS is mixed with the signal. This test file causes the 22 least significant bits to constantly toggle, which produces strong jitter spectral components at the 250Hz rate and its odd harmonics. The test file shows how susceptible the DAC and delivery interface are to jitter, which would manifest as peaks above the noise floor at 500Hz intervals (*e.g.*, 250Hz, 750Hz, 1250Hz, etc.). Note that the alternating peaks are in the test file itself, but at levels of -144dBrA and below. The test file can also be used in conjunction with artificially injected sine-wave jitter by the Audio Precision, to show how well the DAC rejects jitter.

The coaxial input exhibits low-level peaks in the audioband, at -115dBrA and below, at 2kHz and below. This is a good J-test result, indicating that SU-G700M2 DAC should yield good jitter immunity.

**J-Test (optical)**

The chart above shows the results of the J-Test test for the optical digital input measured at the line level output of the SU-G700M2. The optical input exhibits low-level peaks in the audioband, at -115dBrA and below, at 2kHz and below. This result is essentially identical compared to the coaxial input.

**J-Test with 100ns of injected jitter (coaxial)**

Both the coaxial and optical inputs were also tested for jitter immunity by injecting artificial sine-wave jitter at 2kHz, which would manifest as sidebands at 10kHz and 14kHz without any jitter rejection. Jitter immunity proved exceptional—with essentially identical results for both inputs, so only the coaxial is shown—with no visible sidebands at the 100ns jitter level.

**J-Test with 500ns of injected jitter (coaxial)**

Both the coaxial and optical inputs were also tested for jitter immunity by injecting artificial jitter sine-wave jitter at 2kHz, which would manifest as sidebands at 10kHz and 14kHz without any jitter rejection. Jitter immunity proved exceptional, with no visible sidebands at a very high 500ns of injected jitter. The results were the same for both inputs, so only the coaxial is shown. Above this level of jitter, the SU-G700M2 DAC lost sync with the signal with both inputs.

**Wideband FFT spectrum of white noise and 19.1kHz sine-wave tone (coaxial input)**

The chart above shows a fast Fourier transform (FFT) of the SU-G700M2’s line-level output with white noise at -4dBFS (blue/red) and a 19.1 kHz sine wave at 0dBFS fed to the coaxial digital input, sampled at 16/44.1. The steep roll-off around 20kHz in the white-noise spectrum shows the behavior of the SU-G700M2’s reconstruction filter. There are no aliased image peaks within the audioband. The primary aliasing signal at 25kHz is at -95dBrA, while the second and third distortion harmonics (38.2, 57.3kHz) of the 19.1kHz tone are at -80 and -70dBrA.

**RMS level vs. frequency vs. load impedance (1W, left channel only)**

The chart above shows RMS level (relative to 0dBrA, which is 1W into 8 ohms or 2.83Vrms) as a function of frequency, for the analog line-level input swept from 5Hz to 100kHz. The blue plot is into an 8-ohm load, the purple is into a 4-ohm load, the pink plot is an actual speaker (Focal Chora 806, measurements can be found here), and the cyan plot is no load connected. The chart below . . .

. . . is the same but zoomed in to highlight differences. Here we find that at low frequencies (*i.e.*, around 20Hz), the deviations between no load and 4 ohms are at their lowest at 0.3dB, but at high frequencies, the differences are significant, at about 1.5dB at 20kHz. This is a result of the digital amplifier technology used, which exhibits a high damping factor at low frequencies, but a low damping factor at high frequencies (see the damping-factor chart at the end). When a real speaker is used, the major deviations appear once again at high frequencies, with a 0.45dB deviation between 5kHz and 20kHz.

**RMS level vs. frequency (1W, left channel only, real speaker, LPAC on and off)**

The chart above shows RMS level (relative to 0dBrA, which is 1W into 8 ohms or 2.83Vrms) as a function of frequency, for the analog line-level input swept from 20Hz to 20kHz. Both plots are for the Focal Chora 806 speaker, with (blue) and without (purple) LAPC enbaled. The SU-G700M2 provides a feature called Load Adaptive Phase Calibration (LAPC). This feature measures the outputs of the amplifier while the speakers are connected by using test tones to establish a correction curve to deal with the amplifier’s inherently high output impedance at high frequencies. The theoretical goal is to achieve a flat frequency response for the user’s speakers when LAPC is enabled. We can see here that the blue trace is not flat, but closer to ideal compared to when LAPC is disabled. When LAPC is disabled, we are at -0.3dB at 200kHz and 20kHz, compared to the -0.2dB with LAPC enabled.

**THD ratio (unweighted) vs. frequency vs. output power**

The chart above shows THD ratios at the output into 8 ohms as a function of frequency for a sine-wave stimulus at the analog line-level input. The blue and red plots are for the left and right channels at 1W output into 8 ohms, purple/green at 10W, and pink/orange at 63W. The power was varied using the volume control. At 1W, the right channel outperformed the left by about 5dB, and hovered around 0.01% throughout the measured audioband. At 10W, the THD ratios were constant around 0.06% for both channels. The 63W THD values were slightly higher, between 0.1% and 0.07%.

**THD ratio (unweighted) vs. frequency at 10W (MM and MC phono inputs)**

The chart above shows THD ratio as a function of frequency plots for the phono input measured across an 8-ohm load at 10W. The MM configuration is shown in blue/red (left/right) and MC in purple/green (left/right). The input sweep is EQ’d with an inverted RIAA curve. All THD ratios were fairly constant from 20Hz to 6kHz, hovering between 0.06 and 0.07%. The exception is at very low frequencies for the MC configuration, where THD ratios were as high as 0.15% at 30Hz.

**THD ratio (unweighted) vs. output power at 1kHz into 4 and 8 ohms**

The chart above shows THD ratios measured at the output of the SU-G700M2 as a function of output power for the analog line-level input, for an 8-ohm load (blue/red for left/right channels) and a 4-ohm load (purple/green for left/right channels). Both data sets track relatively closely, except for maximum power. There is a dip in THD, from 0.02% down to 0.005% in both data sets that occurs when the output voltage is around 1Vrms (0.1W into 8 ohms, 0.3W into 4 ohms). The “knees” occur at around 70W (8-ohm) and 120W (4-ohm), below which THD values range as low as 0.004% (below 1W) to 0.05% (above 10W). We find that the 8- and 4-ohm data reach the 1% THD mark at 85W and 156W.

**THD+N ratio (unweighted) vs. output power at 1kHz into 4 and 8 ohms**

The chart above shows THD+N ratios measured at the output of the SU-G700M2 as a function of output power for the analog line-level input, for an 8-ohm load (blue/red for left/right channels) and a 4-ohm load (purple/green for left/right channels). Overall, THD+N values for both loads were similar up to 50W, ranging from 0.5%, down to 0.02%, then up to 0.05%.

**THD ratio (unweighted) vs. frequency at 8, 4, and 2 ohms (left channel only)**

The chart above shows THD ratios measured at the output of the SU-G700M2 as a function of frequency into three different loads (8/4/2 ohms) for a constant input voltage that yields 10W at the output into 8 ohms (and roughly 20W into 4 ohms, and 40W into 2 ohms) for the analog line-level input. The 8-ohm load is the blue trace, the 4-ohm load the purple trace, and the 2-ohm load the pink trace. We find roughly the same constant THD values of just above and below 0.05% for the 8- and 4-ohm data, respectively. The 2-ohm data yielded higher THD ratios, hovering around 0.2% across the measured audioband.

**THD ratio (unweighted) vs. frequency into 8 ohms and real speakers (left channel only)**

The chart above shows THD ratios measured at the output of the SU-G700M2 as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). In general, the measured THD ratios for the real speakers were close to the 8-ohm resistive load. The worst-case diffrences were around 25dB at 20Hz (between the Focal and dummy load), and then about 10dB between 100Hz and 200Hz (between the Paradigm and dummy load). Above 500Hz, THD ratios were either very close, or lower with the real speakers compared to the dummy resistive load, hovering around the 0.02% mark.

**IMD ratio (CCIF) vs. frequency into 8 ohms and real speakers (left channel only)**

The chart above shows Intermodulation Distortion (IMD) ratios measured at the output of the SU-G700M2 as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the balanced analog line-level input. Here the CCIF IMD method is used, where the primary frequency is swept from 20kHz (F1) down to 2.5kHz, and the secondary frequency (F2) is always 1kHz lower than the primary, with a 1:1 ratio. The CCIF IMD analysis results are the sum of the second (F1-F2 or 1kHz) and third modulation products (F1+1kHz, F2-1kHz). The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). At high frequerncies, there is a 5-8dB difference between the dummy load (-75dB) and real speaker (-70dB) IMD values. Between 2.5 and 7kHz, IMD ratios were either very close, or lower with the real speakers comapred to the dummy resistive load, hovering around the -80 to -75dB (0.01-0.02%) mark.

**IMD ratio (SMPTE) vs. frequency into 8 ohms and real speakers (left channel only)**

The chart above shows IMD ratios measured at the output of the SU-G700M2 as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the balanced analog line-level input. Here, the SMPTE IMD method is used, where the primary frequency (F1) is swept from 250Hz down to 40Hz, and the secondary frequency (F2) is held at 7kHz with a 4:1 ratio. The SMPTE IMD analysis results consider the second (F2 ± F1) through the fifth (F2 ± 4xF1) modulation products. The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). All three plots yielded roughly the same IMD values, between 0.05% to 0.1% up to 500Hz, then a drop to 0.01%.

**FFT spectrum – 1kHz (line-level input)**

Shown above is the fast Fourier transform (FFT) for a 1kHz input sine-wave stimulus, measured at the output across an 8-ohm load at 10W for the analog line-level input. We see that the signal’s second harmonic, at 2kHz, is at -100/-70dBrA (left/right), or 0.001/0.03%, while the odd harmonics at 3 and 5kHz dominate at -65 and -75dBrA, or 0.06% and 0.03%. There are no power-supply related noise peaks to speak right of the signal peak. There is a rise in the noise above 20kHz, characteristic of digital amplifiers.

**FFT spectrum – 1kHz (digital input, 16/44.1 data at 0dBFS)**

Shown above is the fast Fourier transform (FFT) for a 1kHz input sine-wave stimulus, measured at the output across an 8-ohm load at 10W for the coaxial digital input, sampled at 16/44.1. Signal harmonics are very similar to the analog input FFT above. Here again, there are no power-supply related noise peaks to speak of.

**FFT spectrum – 1kHz (digital input, 24/96 data at 0dBFS)**

Shown above is the fast Fourier transform (FFT) for a 1kHz input sine-wave stimulus, measured at the output across an 8-ohm load at 10W for the coaxial digital input, sampled at 24/96. Signal harmonics are very similar to the analog input FFT above. Here again, there are no power-supply related noise peaks to speak of.

**FFT spectrum – 1kHz (digital input, 16/44.1 data at -90dBFS)**

Shown above is the FFT for a 1kHz -90dBFS dithered 16/44.1 input sine-wave stimulus at the coaxial digital input, measured at the output across an 8-ohm load. We see the 1kHz primary signal peak, at the correct amplitude, and no other peaks above the noise floor at -110dBrA.

**FFT spectrum – 1kHz (digital input, 24/96 data at -90dBFS)**

Shown above is the FFT for a 1kHz -90dBFS dithered 24/96 input sine-wave stimulus at the coaxial digital input, measured at the output across an 8-ohm load. We see the 1kHz primary signal peak, at the correct amplitude, and no other peaks above the noise floor at -110dBrA.

**FFT spectrum – 1kHz (MM phono input)**

Shown above is the FFT for a 1kHz input sine-wave stimulus, measured at the output across an 8-ohm load at 10W for the phono input, configured for MM. We see even and odd signal harmonics up to 20kHz, at -65dBrA, or 0.06%, and below. The most significant signal harmonic peak is at 3kHz. The most significant power-supply-related noise peaks can be seen at 60Hz at -80dBrA, or 0.01%. The second (120Hz) and third (180Hz) noise-related harmonics can also be seen at -105 and -95dBrA, or 0.0006% and 0.002%.

**FFT spectrum – 1kHz (MC phono input)**

Shown above is the FFT for a 1kHz input sine-wave stimulus, measured at the output across an 8-ohm load at 10W for the phono input, configured for MC. We see even and odd signal harmonics up to 20kHz, at -65dBrA, or 0.06%, and below. The most significant signal harmonic peak is at 3kHz. The most significant power-supply-related noise peaks can be seen at 60Hz at -60dBrA, or 0.1%. The second (120Hz), third (180Hz), fourth (240Hz), fifth (300Hz), seventh (420Hz), and ninth (540Hz) noise-related harmonics can also be seen at –70dBrA to -100dBrA, or 0.03% to 0.001%.

**FFT spectrum – 50Hz (line-level input)**

Shown above is the FFT for a 50Hz input sine-wave stimulus measured at the output across an 8-ohm load at 10W for the analog line-level input. The X axis is zoomed in from 40Hz to 1kHz, so that peaks from noise artifacts can be directly compared against peaks from the harmonics of the signal. Even (*e.g.*, 100Hz, 200Hz, etc.) and odd (*e.g.*, 150Hz, 250Hz, etc.) signal harmonics can be seen throughout, at -65dBrA (150Hz), or 0.06%, and below. There are no power-supply noise-related harmonics to be seen.

**FFT spectrum – 50Hz (MM phono input)**

Shown above is the FFT for a 50Hz input sine-wave stimulus measured at the output across an 8-ohm load at 10W for the phono input (MM configuration). The X axis is zoomed in from 40 Hz to 1kHz, so that peaks from noise artifacts can be directly compared against peaks from the harmonics of the signal. The most predominant signal-related harmonic is at 150Hz at -65dBrA, or 0.06%. Higher-order signal harmonics can also be seen at lower amplitudes. The most predominant power-supply noise-related peak is at the 60Hz fundamental at -80dBrA, or 0.01%.

**FFT spectrum – 50Hz (MC phono input)**

Shown above is the FFT for a 50Hz input sine-wave stimulus measured at the output across an 8-ohm load at 10W for the phono input (MC configuration). The X axis is zoomed in from 40 Hz to 1kHz, so that peaks from noise artifacts can be directly compared against peaks from the harmonics of the signal. The most predominant signal-related harmonic is at 100Hz at -65dBrA, or 0.06%. Higher-order signal harmonics can also be seen at lower amplitudes. The most predominant power-supply noise-related peak is at the 60Hz fundamental at -60dBrA, or 0.1%.

**Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, line-level input)**

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sine-wave stimulus tone measured at the output across an 8-ohm load at 10W for the analog line-level input. The input RMS values are set at -6.02dBrA so that, if summed for a mean frequency of 18.5kHz, would yield 10W (0dBrA) into 8 ohms at the output. We find that the second-order modulation product (*i.e.*, the difference signal of 1kHz) is at -80dBRa, or 0.01%, while the third-order modulation products, at 17kHz and 20kHz, are slightly higher at around -75dBrA, or 0.02%.

**Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, coaxial digital input, 16/44.1)**

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sine-wave stimulus tone measured at the output across an 8-ohm load at 10W for the digital coaxial input at 16/44.1. We find that the second-order modulation product (*i.e.*, the difference signal of 1kHz) is at -80dBRa, or 0.01%, while the third-order modulation products, at 17kHz and 20kHz, are slightly higher at around -75dBrA, or 0.02%.

**Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, coaxial digital input, 24/96)**

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sine-wave stimulus tone measured at the output across an 8-ohm load at 10W for the digital coaxial input at 24/96. We find that the second-order modulation product (*i.e.*, the difference signal of 1kHz) is at -80dBRa, or 0.01%, while the third-order modulation products, at 17kHz and 20kHz, are slightly higher at around -75dBrA, or 0.02%.

**Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, MM phono input)**

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sine-wave stimulus tone measured at the output across an 8-ohm load at 10W for the phono input configured for MM. We find that the second-order modulation product (*i.e.*, the difference signal of 1kHz) is at -80dBRa, or 0.01%, while the third-order modulation products, at 17kHz and 20kHz, are slightly higher at around -75dBrA, or 0.02%.

**Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, MC phono input)**

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sine-wave stimulus tone measured at the output across an 8-ohm load at 10W for the phono input configured for MC. We find that the second-order modulation product (*i.e.*, the difference signal of 1kHz) is at -85dBRa, or 0.006%, while the third-order modulation products, at 17kHz and 20kHz, are higher at around -75dBrA, or 0.02%.

**Square-wave response (10kHz)**

Above is the 10kHz squarewave response using the analog line-level input, at roughly 10W into 8 ohms. Due to limitations inherent to the Audio Precision APx555 B Series analyzer, this graph should not be used to infer or extrapolate the SU-G700M2’s slew-rate performance. Rather, it should be seen as a qualitative representation of the SU-G700M2’s mid-tier bandwidth. An ideal squarewave can be represented as the sum of a sine wave and an infinite series of its odd-order harmonics (*e.g.*, 10kHz + 30kHz + 50kHz + 70kHz . . .). A limited bandwidth will show only the sum of the lower-order harmonics, which may result in noticeable undershoot and/or overshoot, and softening of the edges. In this case, because of the digital nature of the amplifier, we see a 768kHz switching frequency (see 1MHz FFT below) riding on top of the squarewave.

**Square-wave response (10kHz, restricted 500kHz bandwidth)**

Above is the same 10kHz squarewave response using the analog line-level input, at roughly 10W into 8 ohms, this time with a 500kHz input bandwidth on the analyzer to filter out the 768kHz switching frequency. We can see significant over/undershoot in the corners of the squarewave, a consequence of the SU-G700M2’s mid-tier bandwidth.

**FFT spectrum (1MHz bandwidth)**

Shown above is the fast Fourier transform (FFT) for a 1kHz input sine-wave stimulus, measured at the output across an 8-ohm load at 10W for the analog line-level input, with an extended 1MHz input bandwidth. This enables us to see the high-frequency noise above 20kHz reaching almost -75dBrA at 300kHz. We also see a clear peak at 768kHz, reaching just past -35dBrA. The peak, as well as the noise, are a result of the digital amplifier technology used in the SU-G700M2, however, they are far above the audioband—and are therefore inaudible—and so high in frequency that any loudspeaker the amplifier is driving should filter it all out anyway.

**Damping factor vs. frequency (20Hz to 20kHz)**

The final graph above is the damping factor as a function of frequency. We can see here the clear trend of a higher damping factor at low frequencies—around 32 from 20Hz to 2000Hz—and then the steep decline down to 12 at 20kHz. This is a limitation of the digital amplifier technology used in the SU-G700M2, and the reason Technics has incorporated their clever Load Adaptive Phase Calibration (LAPC) feature, to compensate for losses into low impedances at high frequencies.

*Diego Estan*

Electronics Measurement Specialist

- Details
- Parent Category: Products
- Category: Amplifier Measurements

Link: reviewed by Dennis Burger on *SoundStage! Access* on November 1, 2022

**General Information**

All measurements taken using an Audio Precision APx555 B Series analyzer.

The PMA-1700NE was conditioned for 1 hour at 1/8th full rated power (~9W into 8 ohms) before any measurements were taken. All measurements were taken with both channels driven, using a 120V/20A dedicated circuit, unless otherwise stated.

The PMA-1700NE offers three line-level analog inputs (RCA); one pair of phono inputs (RCA), configurable for moving magnet (MM) or moving coil (MC), fixed line-level outputs (RCA), main-in inputs (RCA), one digital coaxial input (RCA), two digital optical inputs (TosLink), one digital USB input, two separate speaker-level outputs (A and B), and one headphone output over a 1/4″ TRS connector.

For the purposes of these measurements, the following inputs were evaluated: digital coaxial, analog line-level, as well as phono (MM and MC). Unless otherwise stated, Source Direct mode was engaged, which bypasses bass, treble, and balance functions, and Analog 2 Mode was used for the analog measurements, which disables both front panel display and the digital circuits.

Most measurements were made with a 2Vrms line-level at the analog input, 5mVrms at the MM input, 0.5mVrms at the MC input, and 0dBFS at the digital input. The volume control does not have a numerical display. The signal-to-noise ratio (SNR) measurements were made with the same input signal values but with the volume set to achieve the rated output power of 70W (8 ohms). For comparison, on the line-level input, a SNR measurement was also made with the volume at maximum, where only 0.219Vrms was required to achieve 70W into 8 ohms.

Based on the high accuracy and variability of the left/right volume channel matching (see table below), the PMA-1700NE volume control is likely digitally controlled but operates in the analog domain. The PMA-1700NE offers 5-3dB volume steps between the minimum and 8 o’clock position, and 0.5dB steps for the remainder of the volume range. Overall range is -53.1dB to +40.7dB (line-level input, speaker output).

**Volume-control accuracy (measured at speaker outputs): left-right channel tracking**

Volume position | Channel deviation |

min | 0.108dB |

9 o'clock | 0.052dB |

12 o'clock | 0.054dB |

3 o'clock | 0.071dB |

max | 0.077dB |

**Published specifications vs. our primary measurements**

The table below summarizes the measurements published by Denon for the PMA-1700NE compared directly against our own. The published specifications are sourced from Denon’s website, either directly or from the manual available for download, or a combination thereof. With the exception of frequency response, where the Audio Precision bandwidth was extended to 500kHz, assume, unless otherwise stated, 10W into 8ohms and a measurement input bandwidth of 10Hz to 90kHz, and the worst-case measured result between the left and right channels.

Parameter | Manufacturer | SoundStage! Lab |

Amplifier rated output power into 8 ohms (0.07% THD) | 70W | 89W |

Amplifier rated output power into 4 ohms (0.7% THD) | 140W | 148W |

Frequency response | 5Hz-100kHz (0,-3dB) | 5Hz-100kHz (-0.04,-0.18dB) |

THD (1kHz, 8 ohms, 35W) | 0.01% | 0.002% |

Damping factor (1kHz) | >100 | 376 |

Input sensivity (phono, MM) | 2.5mVrms | 2mVrms |

Input sensivity (phono, MC) | 0.2mVrms | 0.19mVrms |

Input impedance (phono, MM) | 47k ohms | 52.8k ohms |

RIAA deviation (20Hz-20kHz, MM/MC) | ±0.5dB | ±0.5dB |

Phono maximum input (1% THD, 1kHz, MM) | 130mVrms | 160mVrms |

Phono maximum input (1% THD, 1kHz, MC) | 10mVrms | 15.5mVrms |

Input sensitivity (line-level) | 125mVrms | 120mVrms |

Input impedance (line-level) | 19k ohms | 21.5k ohms |

Input sensitivity (ext. pre input) | 0.85Vrms | 0.83Vrms |

Input impedance (ext. pre input) | 47k ohms | 77.1k ohms |

Signal-to-noise ratio (phono, MM, A-weighted, rated output) | 89dB | 87.2dB |

Signal-to-noise ratio (phono, MC, A-weighted, rated output) | 74dB | 67.8dB |

Signal-to-noise ratio (line-level, A-weighted, rated output) | 107dB | 112.1dB |

Our primary measurements revealed the following using the line-level analog input and digital coaxial input (unless specified, assume a 1kHz sine wave at 2Vrms or 0dBFS, 10W output, 8-ohm loading, 10Hz to 90kHz bandwidth):

Parameter | Left channel | Right channel |

Maximum output power into 8 ohms (1% THD+N, unweighted) | 96W | 96W |

Maximum output power into 4 ohms (1% THD+N, unweighted) | 160W | 160W |

Maximum burst output power (IHF, 8 ohms) | 96W | 96W |

Maximum burst output power (IHF, 4 ohms) | 173W | 173W |

Continuous dynamic power test (5 minutes, both channels driven) | passed | passed |

Crosstalk, one channel driven (10kHz) | -81.7dB | -81.2dB |

Damping factor | 377 | 391 |

Clipping no-load output voltage (instantaneous power into 8 ohms) | 29Vrms | 29Vrms |

DC offset | <-4mV | <-7mV |

Gain (preamp section) | 16.7dB | 16.8dB |

Gain (maximum volume) | 45.8dB | 45.9dB |

IMD ratio (CCIF, 18kHz + 19kHz stimulus tones, 1:1) | <-92dB | <-92dB |

IMD ratio (SMPTE, 60Hz + 7kHz stimulus tones, 4:1 ) | <-92dB | <-84dB |

Input impedance (line input) | 21.5k ohms | 21.6k ohms |

Input sensitivity (for rated power, maximum volume) | 122mVrms | 120mVrms |

Noise level (A-weighted) | <88uVmrs | <92uVmrs |

Noise level (unweighted) | <306uVmrs | <320uVmrs |

Output impedance (line-out) | 683 ohms | 693 ohms |

Signal-to-noise ratio (full power, A-weighted, 2Vrms in) | 112.3dB | 112.1dB |

Signal-to-noise ratio (full power, unweighted, 2Vrms in) | 103.8dB | 103.8dB |

Signal-to-noise ratio (full power, A-weighted, max volume) | 97.5dB | 97.4dB |

Dynamic range (full power, A-weighted, digital 24/96) | 110.5dB | 110.4dB |

Dynamic range (full power, A-weighted, digital 16/44.1) | 95.8dB | 96.0dB |

THD ratio (unweighted) | <0.0008% | <0.0020% |

THD ratio (unweighted, digital 24/96) | <0.0006% | <0.0011% |

THD ratio (unweighted, digital 16/44.1) | <0.0008% | <0.0013% |

THD+N ratio (A-weighted) | <0.0013% | <0.0025% |

THD+N ratio (A-weighted, digital 24/96) | <0.0012% | <0.0016% |

THD+N ratio (A-weighted, digital 16/44.1) | <0.0020% | <0.0023% |

THD+N ratio (unweighted) | <0.0035% | <0.0020% |

Minimum observed line AC voltage | 122VAC | 122VAC |

For the continuous dynamic power test, the PMA-1700NE was able to sustain 155W into 4 ohms (~2% THD) using an 80Hz tone for 500ms, alternating with a signal at -10dB of the peak (15.5W) for 5 seconds, for 5 continuous minutes without inducing a fault or the initiation of a protective circuit. This test is meant to simulate sporadic dynamic bass peaks in music and movies. During the test, the top of the PMA-1700NE was warm to the touch, but did not cause discomfort.

Our primary measurements revealed the following using the phono-level input, MM configuration (unless specified, assume a 1kHz 5mVrms sine-wave input, 10W output, 8-ohm loading, 10Hz to 90kHz bandwidth):

Parameter | Left channel | Right channel |

Crosstalk, one channel driven (10kHz) | -69.6dB | -68.9dB |

DC offset | <-4mV | <-7mV |

Gain (default phono preamplifier) | 35.6dB | 35.8dB |

IMD ratio (CCIF, 18kHz + 19kHz stimulus tones, 1:1) | <-86dB | <-87dB |

IMD ratio (CCIF, 3kHz + 4kHz stimulus tones, 1:1) | <-94dB | <-90dB |

Input impedance | 52.8k ohms | 52.0k ohms |

Input sensitivity (to max power with max volume) | 2mVrms | 2mVrms |

Noise level (A-weighted) | <450uVrms | <622uVrms |

Noise level (unweighted) | <1.4mVrms | <1.8mVrms |

Overload margin (relative 5mVrms input, 1kHz) | 30.1dB | 30.1dB |

Signal-to-noise ratio (full rated power, A-weighted) | 89.0dB | 87.2dB |

Signal-to-noise ratio (full rated power, unweighted) | 77.0dB | 77.3dB |

THD (unweighted) | <0.0012% | <0.0018% |

THD+N (A-weighted) | <0.0052% | <0.0070% |

THD+N (unweighted) | <0.016% | <0.019% |

Our primary measurements revealed the following using the phono-level input, MC configuration (unless specified, assume a 1kHz 0.5mVrms sine-wave input, 10W output, 8-ohm loading, 10Hz to 90kHz bandwidth):

Parameter | Left channel | Right channel |

Crosstalk, one channel driven (10kHz) | -63.8dB | -45.9dB |

DC offset | <-4mV | <-7mV |

Gain (default phono preamplifier) | 56.0dB | 56.1dB |

IMD ratio (CCIF, 18kHz + 19kHz stimulus tones, 1:1) | <-78dB | <-75dB |

IMD ratio (CCIF, 3kHz + 4kHz stimulus tones, 1:1) | <-78dB | <-75dB |

Input impedance | 141 ohms | 141 ohms |

Input sensitivity (to max power with max volume) | 193uVrms | 189uVrms |

Noise level (A-weighted) | <4.5mVrms | <6mVrms |

Noise level (unweighted) | <14mVrms | <17mVrms |

Overload margin (relative 5mVrms input, 1kHz) | 29.8dB | 29.8dB |

Signal-to-noise ratio (full rated power, A-weighted) | 69.4dB | 67.8dB |

Signal-to-noise ratio (full rated power, unweighted) | 56.8dB | 56.9dB |

THD (unweighted) | <0.004% | <0.005% |

THD+N (A-weighted) | <0.05% | <0.07% |

THD+N (unweighted) | <0.16% | <0.18% |

Our primary measurements revealed the following using the analog input at the headphone output (unless specified, assume a 1kHz sine wave, 2Vrms output, 300 ohms loading, 10Hz to 90kHz bandwidth):

Parameter | Left channel | Right channel |

Maximum output power into 600 ohms (1% THD+N, unweighted) | 454mW | 454mW |

Maximum output power into 300 ohms (1% THD+N, unweighted) | 449mW | 449mW |

Maximum output power into 32 ohms (1% THD+N, unweighted) | 105mW | 105mW |

Gain | 45.8dB | 45.9dB |

Output impedance | 440 ohms | 441 ohms |

Noise level (A-weighted) | <23uVrms | <23uVrms |

Noise level (unweighted) | <63uVrms | <63uVrms |

Signal-to-noise (A-weighted, ref. max output voltage) | 113.2dB | 113.2dB |

Signal-to-noise (unweighted, ref. max output voltage) | 104.5dB | 104.6dB |

THD ratio (unweighted) | <0.0006% | <0.0006% |

THD+N ratio (A-weighted) | <0.0013% | <0.0013% |

THD+N ratio (unweighted) | <0.0031% | <0.0031% |

**Frequency response (8-ohm loading, line-level input)**

In our frequency-response plots above, measured across the speaker outputs at 10W into 8 ohms, the PMA-1700NE is perfectly flat within the audioband (20Hz to 20kHz) and well beyond. At the extremes, the PMA-1700NE is essentially at 0dB at 5Hz and just below -0.5dB at 200kHz, making “wide bandwidth audio amplifier” an apt descriptor for the PMA-1700NE. In the chart above and most of the charts below, only a single trace may be visible. This is because the left channel (blue or purple trace) is performing identically to the right channel (red or green trace), and so they perfectly overlap, indicating that the two channels are ideally matched.

**Frequency response (8-ohm loading, line-level input, bass and treble controls)**

Above are frequency-response plots measured at the speaker-level outputs into 8 ohms, with the bass and treble controls set to maximum (blue/red plots) and minimum (purple/green plots). We see that for the bass and treble controls, roughly +/-7dB of gain/cut is available at 20Hz and 20kHz.

**Phase response (8-ohm loading, line-level input)**

Above are the phase response plots from 20Hz to 20kHz for the line-level input measured across the speaker outputs at 10W into 8 ohms. The tone controls were not engaged. The PMA-1700NE does not invert polarity and exhibits, at worst, about 30 degrees (at 20kHz) of phase shift within the audioband.

**Frequency response vs. input type (analog and 16/44.1, 24/96, and 24/192 inputs with 8-ohm loading, left channel only)**

The chart above shows the PMA-1700NE’s frequency response as a function of input type measured across the speaker outputs at 10W into 8 ohms. The green trace is the same analog input data from the previous chart (but limited to 80kHz). The blue trace is for a 16-bit/44.1kHz dithered digital input signal from 5Hz to 22kHz using the coaxial input, the purple trace is for a 24/96 dithered digital input signal from 5Hz to 48kHz, and the pink trace is for a 24/192 dithered digital input signal from 5Hz to 96kHz. The 16/44.1 data exhibits brickwall-type filtering, with a -3dB point at 20.9kHz. The 24/96 and 24/192 kHz data yielded -3dB points at 45.4kHz and 59.8kHz, respectively. There is no evidence to suggest that the PMA-1700NE digitizes incoming analog signals.

**Frequency response (8-ohm loading, MM phono input)**

The chart above shows the frequency response for the phono input (MM). What is shown is the deviation from the RIAA curve, where the input signal sweep is EQ’d with an inverted RIAA curve supplied by Audio Precision (*i.e.*, zero deviation would yield a flat line at 0dB). With the PMA-1700NE, we see a maximum deviation within the audioband of about +0.5dB at 20kHz.

**Frequency response (8-ohm loading, MC phono input)**

The chart above shows the frequency response for the phono input (MM). Like the MM chart above, what is shown is the deviation from the RIAA curve, where the input signal sweep is EQ’d with an inverted RIAA curve supplied by Audio Precision (*i.e.*, zero deviation would yield a flat line at 0dB). We see a maximum deviation within the audioband of about +0.4dB between 10kHz and 20kHz.

**Phase response (MM input)**

Above is the phase-response plot from 20Hz to 20kHz for the phono input (MM), measured across the speaker outputs at 10W into 8 ohms. For the phono input, since the RIAA equalization curve must be implemented, which ranges from +19.9dB (20Hz) to -32.6dB (90kHz), phase shift at the output is inevitable. Here we find a worst case of about -60 degrees at 200Hz and 5kHz. The PMA-1700NE does not invert polarity.

**Phase response (MC input)**

Above is the phase-response plot from 20Hz to 20kHz for the phono input (MC), measured across the speaker outputs at 10W into 8 ohms. For the phono input, since the RIAA equalization curve must be implemented, which ranges from +19.9dB (20Hz) to -32.6dB (90kHz), phase shift at the output is inevitable. Here we find a worst case of about -60 degrees at 200Hz and 5kHz. The PMA-1700NE does not invert polarity.

**Digital linearity (16/44.1 and 24/96 data)**

The chart above shows the results of a linearity test for the coaxial digital input for both 16/44.1 (blue/red) and 24/96 (purple/green) input data, measured at the line level output of the PMA-1700NE. The digital input is swept with a dithered 1kHz input signal from -120dBFS to 0dBFS, and the output is analyzed by the APx555. The ideal response would be a straight, flat line at 0dB. Both data were essentially perfect as of -100dBFS down to 0dBFS. At -120dBFS, the 16/44.1 data were only +2 to 2.5dB above reference, while the 24/96 data were within 1dB of reference.

**Impulse response (24/44.1 data)**

The chart above shows the impulse responses for the PMA-1700NE, fed to the coaxial digital input, measured at the line-level output, for a looped 24/44.1 test file that moves from digital silence to full 0dBFS (all “1”s), for one sample period, then back to digital silence. Here we find a symmetrical impulse response with minimal pre- and post-ringing.

**J-Test (coaxial)**

The chart above shows the results of the J-Test test for the coaxial digital input measured at the line-level output of the PMA-1700NE. The J-Test was developed by Julian Dunn in the 1990s. It is a test signal—specifically, a -3dBFS undithered 12kHz squarewave sampled (in this case) at 48kHz (24 bits). Since even the first odd harmonic (*i.e.*, 36kHz) of the 12kHz squarewave is removed by the bandwidth limitation of the sampling rate, we are left with a 12kHz sinewave (the main peak). In addition, an undithered 250Hz squarewave at -144dBFS is mixed with the signal. This test file causes the 22 least-significant bits to constantly toggle, which produces strong jitter spectral components at the 250Hz rate and its odd harmonics. The test file shows how susceptible the DAC and delivery interface are to jitter, which would manifest as peaks above the noise floor at 500Hz intervals (*e.g.*, 250Hz, 750Hz, 1250Hz, etc.). Note that the alternating peaks are in the test file itself, but at levels of -144dBrA and below. The test file can also be used in conjunction with artificially injected sine-wave jitter by the Audio Precision, to show how well the DAC rejects jitter.

The coaxial input exhibits obvious peaks throughout the audioband, as high as -100dBrA on both sides of the 12kHz fundamental. This is a relatively poor J-Test result, indicating that PMA-1700NE DAC may be susceptible to jitter.

**J-Test (optical)**

The chart above shows the results of the J-Test test for the optical digital input measured at the line-level output of the PMA-1700NE. The result is similar but slightly worse than for the coaxial input. The highest peaks are just above -90dBrA, on both sides of the 12kHz fundamental. This is a relatively poor J-Test result, indicating that PMA-1700NE DAC may be susceptible to jitter.

**J-Test with 10ns of injected jitter (coaxial)**

The coaxial input was also tested for jitter immunity by injecting artificial sine-wave jitter at 2kHz, which would manifest as sidebands at 10kHz and 14kHz without any jitter rejection. Jitter immunity proved poor, as predicted based on the previous results, with visible sidebands at only the 10ns jitter level, at -70dBrA.

**J-Test with 100ns of injected jitter (coaxial)**

The coaxial input was also tested for jitter immunity by injecting artificial sine-wave jitter at 2kHz, which would manifest as sidebands at 10kHz and 14kHz without any jitter rejection. Jitter immunity proved poor as predicted, based on the other results, with visible sidebands at the 100ns jitter level, at -50dBrA. The optical input (not shown) performed similarly with the same 100ns jitter level injected.

**Wideband FFT spectrum of white noise and 19.1kHz sine-wave tone (coaxial input)**

The chart above shows a fast Fourier transform (FFT) of the PMA-1700NE’s line-level output with white noise at -4dBFS (blue/red) and a 19.1 kHz sine wave at 0dBFS fed to the coaxial digital input, sampled at 16/44.1. The fairly steep roll-off around 20kHz in the white-noise spectrum shows the behavior of the PMA-1700NE’s reconstruction filter. There are no aliased image peaks within the audioband visible above the -125dBrA noise floor. The primary aliasing signal at 25kHz is highly suppressed at -105dBrA, while the second and third distortion harmonics (38.2, 57.3kHz) of the 19.1kHz tone are at -80dBrA and below.

**RMS level vs. frequency vs. load impedance (1W, left channel only)**

The chart above shows RMS level (relative to 0dBrA, which is 1W into 8ohms or 2.83Vrms) as a function of frequency, for the analog line-level input swept from 5Hz to 100kHz. The blue plot is into an 8-ohm load, the purple is into a 4-ohm load, the pink plot is an actual speaker (Focal Chora 806, measurements can be found here), and the cyan plot is no load connected. The chart below . . .

. . . is the same but zoomed in to highlight differences. Here we find that maximum deviation between no load and a 4-ohm load is very small, at just over 0.04dB. This is an indication of a very high damping factor, or low output impedance. With a real speaker, maximum deviations in RMS level were smaller, at about 0.035dB.

**THD ratio (unweighted) vs. frequency vs. output power**

The chart above shows THD ratios at the output into 8 ohms as a function of frequency for a sine-wave stimulus at the analog line-level input. The blue and red plots are for left and right channels at 1W output into 8 ohms, purple/green at 10W, and pink/orange at 63W. Power was varied using the volume control. The left channel consistently outperformed the right channel by as much as 5dB at all power levels. The 1W and 10W data are nearly identical, ranging between 0.005% at 20Hz, down to 0.0007% from 200Hz to 1kHz, then up to 0.01% at 20kHz for the left channel. The 63W THD values were only slightly higher, from a low of 0.0015% in the midrange frequencies, up to 0.02% at 20kHz for the left channel.

**THD ratio (unweighted) vs. frequency at 10W (MM and MC phono inputs)**

The chart above shows THD ratios as a function of frequency plots for the phono input measured across an 8-ohm load at 10W. The blue and red plots are for left and right channels with the MM configuration, purple/green for MC. The input sweep is EQ’d with an inverted RIAA curve. For the MM configuration, the THD values vary from around 0.02% (20Hz) down to 0.001% (200Hz-1kHz), then up to 0.006% (20kHz), once again for the left channel, which outperformed the right channel by as much as 5dB. For the MC configurationm, the THD values vary from around 0.2% (20Hz) down to 0.003% (1kHz-2kHz), then up to 0.006% (20kHz), once again for the left channel. For the MM input, the left channel outperformed the right channel only between 1kHz to 20kHz.

**THD ratio (unweighted) vs. output power at 1kHz into 4 and 8 ohms**

The chart above shows THD ratios measured at the output of the PMA-1700NE as a function of output power for the analog line-level input, for an 8-ohm load (blue/red for left/right channels) and a 4-ohm load (purple/green for left/right channels). The right channel into 4 ohms exhibited much higher THD ratios (20-30dB) than the left channel between 0.5W and 100W. The test was repeated to rule out any anomalies, and the results were repeatable. Into 8 ohms, the left channel outperformed the right channel by 10dB or less. Both the left channel data (8 and 4 ohms) are quite similar, a testament to the PMA-1700NE’s high damping factor. These ranged from about 0.002% at 50mW, down to nearly 0.0005% at 5-50W, then a small rise to the knees (near 70W into 8 ohms, near 100W into 4 ohms). The 1% THD marks were hit at 96W (8 ohm) and 160W (4 ohm).

**THD+N ratio (unweighted) vs. output power at 1kHz into 4 and 8 ohms**

The chart above shows THD+N ratios measured at the output of the PMA-1700NE as a function of output power for the analog line-level input, for an 8-ohm load (blue/red for left/right channels) and a 4-ohm load (purple/green for left/right channels). Aside from the right channel into 4 ohms (described above), overall, THD+N values for both loads were similar up to 60W. The 8-ohm data ranged from 0.02% down to just below 0.003%. The 8-ohm data outperformed the 4-ohm data by 3-4dB.

**THD ratio (unweighted) vs. frequency at 8, 4, and 2 ohms (left channel only)**

The chart above shows THD ratios measured at the output of the PMA-1700NE as a function of frequency into three different loads (8/4/2 ohms) for a constant input voltage that yields 10W at the output into 8 ohms (and roughly 20W into 4 ohms, and 40W into 2 ohms) for the analog line-level input. The 8-ohm load is the blue trace, the 4-ohm load the purple trace, and the 2-ohm load the pink trace. The 8-ohm and 4-ohm track very closely throughout the audioband, between 0.001% and 0.01%. The 2-ohm data yielded higher distortion, hovering between 0.003% and 0.015% from 20Hz to 20kHz. Overall, this is a good result and shows how stable the PMA-1700NE is into low impedances.

**THD ratio (unweighted) vs. frequency into 8 ohms and real speakers (left channel only)**

The chart above shows THD ratios measured at the output of the PMA-1700NE as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). Aside from an increase in THD ratios for the two-way speaker below 40Hz, rising as high as 0.03% at 20Hz, all three plots are remarkebly close. This is yet another example showing how impervious the PMA-1700NE is to various loads due to its very high damping factor. Overall, THD ratios varied from 0.0005% to 0.01%.

**IMD ratio (CCIF) vs. frequency into 8 ohms and real speakers (left channel only)**

The chart above shows intermodulation distortion (IMD) ratios measured at the output of the PMA-1700NE as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. Here the CCIF IMD method is used, where the primary frequency is swept from 20kHz (F1) down to 2.5kHz, and the secondary frequency (F2) is always 1kHz lower than the primary, with a 1:1 ratio. The CCIF IMD analysis results are the sum of the second (F1-F2 or 1kHz) and third modulation products (F1+1kHz, F2-1kHz). The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). All three data sets track fairly closely, with the expection of the three-way speaker showing higher IMD values above 10kHz, differing by almost 10dB at 20kHz. Overall IMD ratios were hovering around 0.001%.

**IMD ratio (SMPTE) vs. frequency into 8 ohms and real speakers (left channel only)**

The chart above shows IMD ratios measured at the output of the PMA-1700NE as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. Here, the SMPTE IMD method is used, where the primary frequency (F1) is swept from 250Hz down to 40Hz, and the secondary frequency (F2) is held at 7kHz with a 4:1 ratio. The SMPTE IMD analysis results consider the second (F2 ± F1) through the fifth (F2 ± 4xF1) modulation products. The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). All three data sets are close enough to be judged as identical, hovering around the 0.003% mark.

**FFT spectrum – 1kHz (line-level input, Analog Mode turned on)**

Shown above is the fast Fourier transform (FFT) for a 1kHz input sine-wave stimulus, measured at the output across an 8-ohm load at 10W for the analog line-level input. We see that the signal’s second harmonic, at 2kHz, is at -100/95dBrA (left/right), or 0.001/0.002%, while all subsequent harmonics are below the -110dBrA, or 0.0003% mark. Power-supply-related noise at the fundamental (60Hz) frequency, as well as both even and odd harmonics, are evident, at -100dBrA, or 0.001%, levels and below.

**FFT spectrum – 1kHz (line-level input, Analog Mode turned off)**

Shown above is the fast Fourier transform (FFT) for a 1kHz input sine-wave stimulus, measured at the output across an 8-ohm load at 10W for the analog line-level input, with Analog 2 Mode turned off (*i.e.*, with the front display and digital electronics turned on). We see effectively no difference when compared with the FFT above with Analog Mode engaged.

**FFT spectrum – 1kHz (digital input, 16/44.1 data at 0dBFS)**

Shown above is the fast Fourier transform (FFT) for a 1kHz input sine-wave stimulus, measured at the output across an 8-ohm load at 10W for the coaxial digital input, sampled at 16/44.1. Signal harmonics and power-supply-related noise peaks are very similar in level to the analog input FFT above, although with a higher noise floor due to the limitations of the 16-bit depth.

**FFT spectrum – 1kHz (digital input, 24/96 data at 0dBFS)**

Shown above is the fast Fourier transform (FFT) for a 1kHz input sine-wave stimulus, measured at the output across an 8-ohm load at 10W for the coaxial digital input, sampled at 24/96. Signal harmonics and power-supply-related noise peaks are very similar in level to the analog input FFT above.

**FFT spectrum – 1kHz (digital input, 16/44.1 data at -90dBFS)**

Shown above is the FFT for a 1kHz -90dBFS dithered 16/44.1 input sine-wave stimulus at the coaxial digital input, measured at the output across an 8-ohm load. We see the 1kHz primary signal peak, at the correct amplitude, and low-level power-supply-related noise harmonics at -105dBrA, or 0.0006%, and below.

**FFT spectrum – 1kHz (digital input, 24/96 data at -90dBFS)**

Shown above is the FFT for a 1kHz -90dBFS dithered 24/96 input sine-wave stimulus at the coaxial digital input, measured at the output across an 8-ohm load. We see the 1kHz primary signal peak, at the correct amplitude, and power-supply-related noise harmonics at -105dBrA, or 0.0006%, and below.

**FFT spectrum – 1kHz (MM phono input)**

Shown above is the FFT for a 1kHz input sine-wave stimulus, measured at the output across an 8-ohm load at 10W for the MM phono configuration. We see the second (2kHz) and third (3kHz) signal harmonics at low levels: -100 and -110dBrA, respectively, or 0.001% and 0.0003%. Power-supply-related odd harmonics, and the fundamental, can be seen at 60, 180 and 300Hz at -80dBrA, or 0.01%. Even-order power-supply-related peaks (120, 240, 360Hz, etc) can also be seen but at lower amplitudes.

**FFT spectrum – 1kHz (MC phono input)**

Shown above is the FFT for a 1kHz input sine-wave stimulus, measured at the output across an 8-ohm load at 10W for the MC phono configuration. Signal related harmonics are difficult to distinguish from the high-order power-supply-related noise harmonics that dominate the FFT. These range from -60dBrA, or 0.1%, at low frequencies (60/180/300Hz), down to -100dBrA, or 0.001%, at high frequencies.

**FFT spectrum – 50Hz (line-level input)**

Shown above is the FFT for a 50Hz input sine-wave stimulus measured at the output across an 8-ohm load at 10W for the analog line-level input. The X axis is zoomed in from 40Hz to 1kHz, so that peaks from noise artifacts can be directly compared against peaks from the harmonics of the signal. The most dominant (non-signal) peaks are the second signal harmonic (100Hz) at -95dBrA (right), or 0.002%, and the second power-supply-related harmonic (120Hz), also at -95dBrA.

**FFT spectrum – 50Hz (MM phono input)**

Shown above is the FFT for a 50Hz input sine-wave stimulus measured at the output across an 8-ohm load at 10W for the MM phono configuration. The X axis is zoomed in from 40 Hz to 1kHz, so that peaks from noise artifacts can be directly compared against peaks from the harmonics of the signal. The most predominant (non-signal) peaks are from the 60Hz power supply fundamental at -80dBrA, or 0.01%, and its third and fifth harmonics (180/300Hz) at the same level. The highest signal related harmonic is at 100Hz, at -100/95dBrA (left/right), or 0.001/0.002%.

**FFT spectrum – 50Hz (MC phono input)**

Shown above is the FFT for a 50Hz input sine-wave stimulus measured at the output across an 8-ohm load at 10W for the MC phono configuration. The X axis is zoomed in from 40 Hz to 1kHz, so that peaks from noise artifacts can be directly compared against peaks from the harmonics of the signal. The most predominant (non-signal) peaks are from the 60Hz power supply fundamental at -60dBrA, or 0.1%, and its third and fifth harmonics (180/300Hz) at the same level. The highest signal related harmonic is at 100Hz, at -90dBrA, or 0.003%.

**Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, line-level input)**

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sine-wave stimulus tone measured at the output across an 8-ohm load at 10W for the analog line-level input. The input RMS values are set at -6.02dBrA so that, if summed for a mean frequency of 18.5kHz, would yield 10W (0dBrA) into 8 ohms at the output. We find that the second-order modulation product (*i.e.*, the difference signal of 1kHz) is at -110/100dBrA (left/right), or 0.0003/0.001%, while the third-order modulation products, at 17kHz and 20kHz, are just above (left) and below (right) -110dBrA, or 0.0003%.

**Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, coaxial digital input, 16/44.1)**

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sine-wave stimulus tone measured at the output across an 8-ohm load at 10W for the digital coaxial input at 16/44.1. We find that the second-order modulation product (*i.e.*, the difference signal of 1kHz) is at -110/100dBrA (left/right), or 0.0003/0.001%, while the third-order modulation products, at 17kHz and 20kHz, are just below -110dBrA, or 0.0003%.

**Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, coaxial digital input, 24/96)**

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the output across an 8-ohm load at 10W for the digital coaxial input at 24/96. We find that the second-order modulation product (*i.e.*, the difference signal of 1kHz) is at -110/100dBrA (left/right), or 0.0003/0.001%, while the third-order modulation products, at 17kHz and 20kHz, are just below -110dBrA, or 0.0003%.

**Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, MM phono input)**

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sine-wave stimulus tone measured at the output across an 8-ohm load at 10W for the MM phono input. We find that the second-order modulation product (*i.e.*, the difference signal of 1kHz) is at -110/100dBrA (left/right), or 0.0003/0.001%, while the third-order modulation products, at 17kHz and 20kHz, are just below -100dBrA, or 0.001%.

**Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, MC phono input)**

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sine-wave stimulus tone measured at the output across an 8-ohm load at 10W for the MC phono configuration. We find that the second-order modulation product (*i.e.*, the difference signal of 1kHz), while difficult to spot below the power-supply-related high-order noise harmonics, is at -100/90dBrA (left/right), or 0.001/0.003%, while the third-order modulation products, at 17kHz and 20kHz, are just below -100dBrA, or 0.001%.

**Squarewave response (10kHz)**

Above is the 10kHz squarewave response using the analog line-level input, at roughly 10W into 8 ohms. Due to limitations inherent to the Audio Precision APx555 B Series analyzer, this graph should not be used to infer or extrapolate the PMA-1700NE ’s slew-rate performance. Rather, it should be seen as a qualitative representation of the PMA-1700NE ’s extended bandwidth. An ideal squarewave can be represented as the sum of a sine wave and an infinite series of its odd-order harmonics (*e.g.*, 10kHz + 30kHz + 50kHz + 70kHz . . .). A limited bandwidth will show only the sum of the lower-order harmonics, which may result in noticeable undershoot and/or overshoot, and softening of the edges. The PMA-1700NE’s squarewave response is superb, showing no visible over/undershoot, or ringing near the sharp corners.

**Damping factor vs. frequency (20Hz to 20kHz)**

The final graph above is the damping factor as a function of frequency. We see a relatively constant and very high damping factor, and both channels tracking closely, between 400 and 350 from 20Hz to 20kHz. This is an exceptional result for an integrated amplifier.

*Diego Estan*

Electronics Measurement Specialist

- Details
- Parent Category: Products
- Category: Amplifier Measurements

Link: reviewed by Vince Hanada on *SoundStage! Simplifi* on September 15, 2022

**General Information**

All measurements taken using an Audio Precision APx555 B Series analyzer.

The Roksan Attessa streaming integrated amplifier was conditioned for 1 hour at 1/8th full rated power (~10W into 8 ohms) before any measurements were taken. All measurements were taken with both channels driven, using a 120V/20A dedicated circuit, unless otherwise stated.

The Attessa offers two unbalanced line-level analog inputs (RCA), one unbalanced moving-magnet (MM) phono input, two coaxial (RCA) and two optical (TosLink) S/PDIF digital inputs, one pair of line-level pre-outs (RCA), and two pairs of speaker-level outputs. On the front of the unit is a 1/8″ TRS headphone output. For the purposes of these measurements, the following inputs were evaluated: digital coaxial, and the analog line-level and MM unbalanced inputs.

The Atessa offers different gain settings (Low, Mid, High) for both the line-level and phono analog inputs. Unless otherwise stated, the default settings of Low for the line-level input and Mid for the phono input were used.

Most measurements were made with a standard 2Vrms line-level analog input, 5mVrms MM input, and 0dBFS digital input. The signal-to-noise ratio (SNR) measurements were made with the same input signal values, but with the volume set to achieve the rated output power of 80W (8 ohms). For comparison, on the line-level input, a SNR measurement was also made with the volume at maximum, where only 0.45Vrms was required to achieve 80W into 8ohms.

Based on the accuracy and non-repeatable results at various volume levels of the left/right channel matching (see table below), the Attessa volume control is likely digitally controlled but operating in the analog domain. The volume control offers a total of 40 steps using 20 LEDs as indicators for positioning. These indicators will either glow dimly or brightly, depending on voluem position. The volume range measured from -40.1dB (position 1) to +34.9dB (maximum) measured between the line-level analog input and the speaker outputs, in increments of 3dB below step 6, 2dB from 6 to 28, 1dB from 29 to 36, then back to 2dB increments from 37 to 40.

**Volume-control accuracy (measured at speaker outputs): left-right channel tracking**

Volume position | Channel deviation |

min | 0.076dB |

25% | 0.081dB |

50% | 0.002dB |

75% | 0.002dB |

100% | 0.006dB |

**Published specifications vs. our primary measurements**

The table below summarizes the measurements published by Roskan for the Attessa compared directly against our own. The published specifications are sourced from Roskan’s website, either directly or from the manual available for download, or a combination thereof.

Parameter | Manufacturer | SoundStage! Lab |

Rated output power into 8 ohms (0.1% THD, 1kHz) | 80W | 81.5W |

Rated output power into 4 ohms (0.1% THD, 1kHz) | 130W | 132W |

Our primary measurements revealed the following using the line-level analog input and digital coaxial input (unless specified, assume a 1kHz sine wave at 2Vrms or 0dBFS, 10W output, 8-ohm loading, 10Hz to 90kHz bandwidth):

Parameter | Left channel | Right channel |

Maximum output power into 8 ohms (1% THD+N, unweighted) | 83W | 83W |

Maximum output power into 4 ohms (1% THD+N, unweighted) | 134W | 134W |

Maximum burst output power (IHF, 8 ohms) | 90.1W | 90.1W |

Maximum burst output power (IHF, 4 ohms) | 156.6W | 156.6W |

Continuous dynamic power test (5 minutes, both channels driven) | passed | passed |

Crosstalk, one channel driven (10kHz) | 80.9dB | 77.2dB |

Damping factor | 196 | 205 |

Clipping no-load output voltage | 29.13Vrms | 29.13Vrms |

DC offset | <11mV | <-13mV |

Gain (pre-out) | 5.8dB | 5.8dB |

Gain (Low, maximum volume) | 34.9dB | 34.9dB |

Gain (Mid, maximum volume) | 40.9dB | 41.0dB |

Gain (High, maximum volume) | 46.9dB | 47.0dB |

IMD ratio (CCIF, 18kHz + 19kHz stimulus tones, 1:1) | <-79.5dB | <-84.5dB |

IMD ratio (SMPTE, 60Hz + 7kHz stimulus tones, 4:1 ) | <-72.5dB | <-83.0dB |

Input impedance (line input, RCA) | 29.5k ohms | 29.3k ohms |

Input sensitivity (Low, for rated power, maximum volume) | 452mVrms | 452mVrms |

Noise level (A-weighted) | <265uVrms | <935uVrms |

Noise level (unweighted) | <520uVrms | <1740uVrms |

Output impedance (pre-out) | 23.0 ohms | 23.2 ohms |

Signal-to-noise ratio (full rated power, A-weighted, 2Vrms in) | 101.4dB | 93.1dB |

Signal-to-noise ratio (full rated power, unweighted, 2Vrms in) | 95.8dB | 90.1dB |

Signal-to-noise ratio (full rated power, A-weighted, max volume) | 93.0dB | 90.3dB |

Dynamic range (full rated power, A-weighted, digital 24/96) | 103.6dB | 95.1dB |

Dynamic range (full rated power, A-weighted, digital 16/44.1) | 95.5dB | 92.7dB |

THD ratio (unweighted) | <0.0076% | <0.0029% |

THD ratio (unweighted, digital 24/96) | <0.0087% | <0.0041% |

THD ratio (unweighted, digital 16/44.1) | <0.0086% | <0.0039% |

THD+N ratio (A-weighted) | <0.0093% | <0.0115% |

THD+N ratio (A-weighted, digital 24/96) | <0.0105% | <0.0121% |

THD+N ratio (A-weighted, digital 16/44.1) | <0.0163% | <0.0173% |

THD+N ratio (unweighted) | <0.0097% | <0.0197% |

Minimum observed line AC voltage | 122VAC | 122VAC |

For the continuous dynamic power test, the Attessa was able to sustain 139W into 4 ohms (~1% THD) using an 80Hz tone for 500ms, alternating with a signal at -10dB of the peak (13.9W) for 5 seconds, for 5 continuous minutes without the protection circuit shutting down the unit. This test is meant to simulate sporadic dynamic bass peaks in music and movies. During the test, the top of the Attessa was warm to the touch, but not enough to induce pain.

Our primary measurements revealed the following using the phono-level input, MM configuration (unless specified, assume a 1kHz 5mVrms sine wave input, 10W output, 8-ohm loading, 10Hz to 90kHz bandwidth):

Parameter | Left channel | Right channel |

Crosstalk, one channel driven (10kHz) | 62.5dB | 57.6dB |

DC offset | <13mV | <-14mV |

Gain (Low - default phono preamplifier) | 43.7dB | 43.6dB |

Gain (Mid - default phono preamplifier) | 49.6dB | 49.7dB |

Gain (High - default phono preamplifier) | 55.7dB | 55.7dB |

IMD ratio (CCIF, 18kHz + 19kHz stimulus tones, 1:1) | <-72dB | <-76dB |

IMD ratio (CCIF, 3kHz + 4kHz stimulus tones, 1:1) | <-76dB | <-84dB |

Input impedance | 52.6k ohms | 51.8k ohms |

Input sensitivity (Mid - to max power with max volume) | 1.47mVrms | 1.49mVrms |

Noise level (A-weighted) | <0.65mVrms | <1.05mVrms |

Noise level (unweighted) | <3.5mVrms | <3.5mVrms |

Overload margin (relative 5mVrms input, 1kHz) | 23.9dB | 23.9dB |

Signal-to-noise ratio (full rated power, A-weighted) | 83.0dB | 82.6dB |

Signal-to-noise ratio (full rated power, unweighted) | 69.9dB | 69.7dV |

THD (unweighted) | <0.0095% | <0.0031% |

THD+N (A-weighted) | <0.013% | <0.013% |

THD+N (unweighted) | <0.04% | <0.04% |

Our primary measurements revealed the following using the analog input at the headphone output (unless specified, assume a 1kHz sine wave, 2Vrms output, 300 ohms loading, 10Hz to 90kHz bandwidth):

Parameter | Left channel | Right channel |

Maximum output power into 600 ohms (1% THD+N, unweighted) | 102mW | 102mW |

Maximum output power into 300 ohms (1% THD+N, unweighted) | 168mW | 168mW |

Maximum output power into 32 ohms (1% THD+N, unweighted) | 40mW | 40mW |

Gain | 17.8dB | 17.9dB |

Output impedance | 6.3 ohms | 6.5 ohms |

Noise level (A-weighted) | <9.5uVrms | <9.5uVrms |

Noise level (unweighted) | <22uVrms | <22uVrms |

Signal-to-noise ratio (A-weighted, ref. max output voltage) | 106.6dB | 106.5dB |

Signal-to-noise ratio (unweighted, ref. max output voltage) | 99.7dB | 99.66dB |

THD ratio (unweighted) | <0.00023% | <0.00023% |

THD+N ratio (A-weighted) | <0.00055% | <0.00055% |

THD+N ratio (unweighted) | <0.00118% | <0.00118% |

**Frequency response (8-ohm loading, line-level input)**

In our measured frequency-response chart above, the Attessa is nearly flat within the audioband (+0.16dB at 20Hz, -0.44dB at 20kHz). At the extremes, the Attessa is +3dB at 5Hz and -6.3dB at 80kHz. The -3dB point was measured around 54kHz. In the graph above and most of the graphs below, only a single trace may be visible. This is because the left channel (blue or purple trace) is performing identically to the right channel (red or green trace), and so they perfectly overlap, indicating that the two channels are ideally matched.

**Phase response (8-ohm loading, line-level input)**

Above are the phase response plots from 20Hz to 20kHz for the line level input, measured across the speaker outputs at 10W into 8 ohms. The Attessa does not invert polarity and exhibits, at worst, less than 30 degrees (at 20kHz) of phase shift within the audioband.

**Frequency response vs. input type (analog and 16/44.1, 24/96, and 24/192 inputs with 8-ohm loading, left channel only)**

The chart above shows the Attessa‘s frequency response as a function of input type measured across the speaker outputs at 10W into 8 ohms. The green trace is the same analog input data from the previous graph. The blue trace is for a 16-bit/44.1kHz dithered digital input signal from 5Hz to 22kHz using the coaxial digital input, and the purple trace is for a 24/96 dithered digital input signal from 5Hz to 48kHz, while the pink trace is for a 24/192 dithered digital input signal from 5Hz to 96kHz. The 16/44.1 data does not exhibit brick-wall type filtering, with a -3dB point at 20.5kHz. The 24/96 and 24/192 kHz data both yielded -3dB points at 31.1kHz. The analog input shows more extended response at high frequencies than the 24/192 input. There’s no evidence that the Attessa digitizes incoming analog signals.

**Frequency response (8-ohm loading, MM phono input)**

The chart above shows the frequency response for the MM phono input. What is shown is the deviation from the RIAA curve, where the input signal sweep is EQ’d with an inverted RIAA curve supplied by Audio Precision (*i.e.*, zero deviation would yield a flat line at 0dB). We see a maximum deviation of about +1dB at 20Hz and -0.5dB at 20kHz, from 20Hz to 20kHz.

**Phase response (MM input)**

Above is the phase response plot from 20Hz to 20kHz for the MM phono input, measured across the speaker outputs at 10W into 8 ohms. The Attessa does not invert polarity. For the phono input, since the RIAA equalization curve must be implemented, which ranges from +19.9dB (20Hz) to -32.6dB (90kHz), phase shift at the output is inevitable. Here we find a worst case of about -60 degrees at 200Hz and 5kHz.

**Digital linearity (16/44.1 and 24/96 data)**

The chart above shows the results of a linearity test for the coaxial digital input for both 16/44.1 (blue/red) and 24/96 (purple/green) input data, measured at the line level pre-outs of the Attessa for a 1Vrms (at 0dBFS) output signal. The digital input is swept with a dithered 1kHz input signal from -120dBFS to 0dBFS, and the output is analyzed by the APx555. The ideal response would be a straight flat line at 0dB. Both data were essentially perfect as of -100dBFS up to 0dBFS. At -120dBFS, the 16/44.1 data were about +2dB above reference, while the 24/96 data were within 1dB of reference. This is a good linearity test result.

**Impulse response (24/44.1 data)**

The graph above shows the impulse response for a looped 24/44.1 test file that moves from digital silence to full 0dBFS (all “1”s) for one sample period then back to digital silence, measured at the line-level pre-outs of the Attessa. We can see that the Attessa DAC utilizes a reconstruction filter that has less pre-ringing than post-ringing.

**J-Test (coaxial)**

The chart above shows the results of the J-Test test for the coaxial digital input measured at the line level pre-outs of the Attessa. J-Test was developed by Julian Dunn in the 1990s. It is a test signal—specifically a -3dBFS undithered 12kHz square wave sampled (in this case) at 48kHz (24 bits). Since even the first odd harmonic (*i.e.*, 36kHz) of the 12kHz square wave is removed by the bandwidth limitation of the sampling rate, we are left with a 12kHz sine wave (the main peak). In addition, an undithered 250Hz square wave at -144dBFS is mixed with the signal. This test file causes the 22 least-significant bits to constantly toggle, which produces strong jitter spectral components at the 250Hz rate and its odd harmonics. The test file shows how susceptible the DAC and delivery interface are to jitter, which would manifest as peaks above the noise floor at 500Hz intervals (*e.g.*, 250Hz, 750Hz, 1250Hz, etc.). Note that the alternating peaks are in the test file itself, but at levels of -144dBrA and below. The test file can also be used in conjunction with artificially injected sine-wave jitter by the Audio Precision, to show how well the DAC rejects jitter.

The coaxial input exhibits peaks within the audioband as high as -110dBrA near the 12kHz fundamental. This is an average J-test result, indicating that the Attessa DAC may be susceptible to jitter.

**J-Test (optical)**

The optical input peformed worse than the coaxial input, exhibiting peaks within the audioband as high as -100dBrA near the 12kHz fundamental.

**J-Test with 10ns of injected jitter (coaxial)**

The coaxial input was also tested for jitter immunity by injecting artificial sine-wave jitter at 2kHz, which would manifest as sidebands at 10kHz and 14kHz without any jitter rejection. Jitter immunity proved poor here, with visible sidebands at -70dBrA with only 10ns of jitter level.

**J-Test with 100ns of injected jitter (coaxial)**

The coaxial input was also tested for jitter immunity by injecting artificial sine-wave jitter at 2kHz, which would manifest as sidebands at 10kHz and 14kHz without any jitter rejection. Jitter immunity proved poor, with visible sidebands at -50dBrA with 100ns of jitter level.

**J-Test with 100ns of injected jitter (optical)**

The optical input was also tested for jitter immunity by injecting artificial sine-wave jitter at 2kHz, which would manifest as sidebands at 10kHz and 14kHz without any jitter rejection. Jitter immunity proved poor again, with visible sidebands at -50dBrA with 100ns of jitter level.

**Wideband FFT spectrum of white noise and 19.1kHz sine-wave tone (coaxial input)**

The plot above shows a fast Fourier transform (FFT) of the Attessa’s line-level pre-outs with white noise at -4 dBFS (blue/red) and a 19.1 kHz sine wave at -3dBFS (at 0dBFS, or 1Vrms, visible distortion was visible) fed to the coaxial digital input, sampled at 16/44.1. The slow roll-off above 20kHz in the white-noise spectrum shows that a brick-wall type reconstruction filter is not used. As a consequence, there are clear aliased image peaks in the audioband at -95dBrA at 13.2kHz, and at -110dBrA between 5 and 10kHz. The main 25kHz alias peak is just below -10dBrA.

**RMS level vs. frequency vs. load impedance (1W, left channel only)**

The chart above shows RMS level (relative to 0dBrA, which is 1W into 8 ohms, or 2.83Vrms) as a function of frequency, for the analog line-level input swept from 5Hz to 100kHz. The blue plot is into an 8-ohm load, the purple is into a 4-ohm load, the pink plot is an actual speaker (Focal Chora 806, measurements can be found here), and the cyan plot is no load connected. The chart below . . .

. . . is the same but zoomed in to highlight differences. Here we can see a maximum deviation within the audioband of about 0.1dB from 4 ohms to no load, which is an indication of a relatively high damping factor, or low output impedance. The maximum variation in RMS level when a real speaker is roughly the same, deviating by about 0.1dB within the flat portion of the curve (50Hz to 10kHz). Note that the dip in RMS level at higher frequencies, and rise at lower frequencies, is a result of the frequency response of the Attessa, and not a damping factor issue.

**THD ratio (unweighted) vs. frequency vs. output power**

The chart above shows THD ratios at the output into 8 ohms as a function of frequency for a sine-wave stimulus at the analog line-level input. The blue and red plots are for left and right channels at 1W output into 8 ohms, purple/green at 10W, and pink/orange at 77W. The power was varied using the volume control. At 1 and 10W, THD ratios are similar, with the right channel out-performing the left channel between 200Hz and 5kHz by as much as 5dB. Left channel THD ratios were roughly flat from 20Hz to 20kHz at 1 and 10W, hovering around 0.006-0.007%. At 77W, THD ratios varied wildly, starting above 1% at 20Hz, then down to 0.008% between 50 and 100Hz, then peaking again at nearly 1% at 3-4kHz, then back down to 0.01% at 20kHz.

**THD ratio (unweighted) vs. frequency at 10W (MM phono input)**

The chart above shows THD ratios as a function of frequency plots for the MM phono input measured across an 8-ohm load at 10W. The input sweep is EQ’d with an inverted RIAA curve. The THD values for the MM configuration vary from around 0.03% (20Hz) down to 0.002% for the right channel at 1.5kHz. The left channel was flat around 0.01% THD from 50Hz to 20kHz.

**THD ratio (unweighted) vs. output power at 1kHz into 4 and 8 ohms**

The chart above shows THD ratios measured at the output of the Attessa as a function of output power for the analog line-level input, for an 8-ohm load (blue/red for left/right channels) and a 4-ohm load (purple/green for left/right channels). The 8-ohm data out-performed the 4-data by about 5dB, and the right channel outperformed the left channel by about the same amount. THD ratios ranged from 0.02% down to 0.002% before the “knees,” which are seen at just below 80W into 8 ohms, and around 130W into 4 ohms. The 1% THD marks were seen at 83W and 134W into 8 and 4 ohms, respectively.

**THD+N ratio (unweighted) vs. output power at 1kHz into 4 and 8 ohms**

The chart above shows THD+N ratios measured at the output of the Attessa as a function of output power for the line-level input, for an 8-ohm load (blue/red for left/right channels) and a 4-ohm load (purple/green for left/right channels). While THD ratios were lower for the right channel compared to the left, noise levels were the opposite, with the right channel exhibiting nearly 10dB more noise (also see FFTs below) than the left channel. Overall, THD+N values for both loads ranged from 0.2% down to 0.01% before the “knees.”

**THD ratio (unweighted) vs. frequency at 8, 4, and 2 ohms (left channel only)**

The chart above shows THD ratios measured at the output of the Attessa as a function of frequency into three different loads (8/4/2 ohms) for a constant input voltage that yields 10W at the output into 8 ohms (and roughly 20W into 4 ohms, and 40W into 2 ohms) for the analog line-level input. The 8-ohm load is the blue trace, the 4-ohm load the purple trace, and the 2-ohm load the pink trace. The 8-ohm data clearly yielded the lowest THD ratios, from 0.007% at 20Hz, down to 0.005% at 3kHz, then up to 0.01% at 20kHz. The 4-ohm data was roughly 5dB higher in THD compared to the 8-ohm data, while the 2-ohm data was nearly 10dB higher than the 4-ohm data between 20Hz and 1kHz, then as much as 20dB higher at 20kHz.

**THD ratio (unweighted) vs. frequency into 8 ohms and real speakers (left channel only)**

The chart above shows THD ratios measured at the output of the Attessa as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). Both speaker THD plots show signficant differences compared to the 8-ohm resistve load, which ranged from 0.005% to just over 0.01%. The 2-way Focal presented the most difficult load for the Attessa in terms of THD, with ratios fluctuating from as high as 0.07% at 20Hz, down to 0.001% at 2kHz. The three-way Paradigm yielded flatter results, with THD peaks at 0.02% at 100Hz and 20kHz, and dipping down to 0.003% at 4kHz.

**IMD ratio (CCIF) vs. frequency into 8 ohms and real speakers (left channel only)**

The chart above shows intermodulation distortion (IMD) ratios measured at the output of the Attessa as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. Here the CCIF IMD method is used, where the primary frequency is swept from 20kHz (F1) down to 2.5kHz, and the secondary frequency (F2) is always 1kHz lower than the primary, with a 1:1 ratio. The CCIF IMD analysis results are the sum of the second (F1-F2 or 1kHz) and third modulation products (F1+1kHz, F2-1kHz). The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). The 8-ohm resistive load yielded flat IMD results across the measurement range, around 0.006-0.007%. The two-way Focal yielded lower IMD results at low frequencies (0.0015% at 2.5kHz), rising up to 0.008% at 20kHz. The three-way Paradigm yiedled IMD results as low as 0.003% at 3kHz, and as high as 0.02% at 20kHz.

**IMD ratio (SMPTE) vs. frequency into 8 ohms and real speakers (left channel only)**

The chart above shows IMD ratios measured at the output of the Attessa as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. Here, the SMPTE IMD method is used, where the primary frequency (F1) is swept from 250Hz down to 40Hz, and the secondary frequency (F2) is held at 7kHz with a 4:1 ratio. The SMPTE IMD analysis results consider the second (F2 ± F1) through the fifth (F2 ± 4xF1) modulation products. The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). All three results are nearly identical, with flat IMD results howevering around 0.015%.

**FFT spectrum – 1kHz (line-level input)**

Shown above is the fast Fourier transform (FFT) for a 1kHz input sine-wave stimulus, measured at the output across an 8-ohm load at 10W for the analog line-level input. We find the second and fourth signal harmonics (2/4kHz) dominate at -80/-90dBrA (left/right), or 0.01/0.003%, and at -100/-110dBrA (left/right), or 0.001/0.0003%. On the left side of the main signal peak, we find the odd harmonics (180/300/420Hz) of the power-supply fundamental dominating with levels around -90/-80dBrA (left/right) and below, or 0.003/0.01%. As was seen in the THD and THD+N versus Output Power graphs above, the left channel exhibits higher THD while the right channel exhibits higher noise.

**FFT spectrum – 1kHz (digital input, 16/44.1 data at 0dBFS)**

Shown above is the fast Fourier transform (FFT) for a 1kHz input sine-wave stimulus, measured at the output across an 8-ohm load at 10W for the coaxial digital input, sampled at 16/44.1. We find roughly the same signal and noise-related harmonics dominating within the audioband, and at the same levels, as seen in the analog FFT above. The significant peaks at 43.1 and 45.1kHz are IMD products between the 1kHz signal and the 44.1kHz sample rate.

**FFT spectrum – 1kHz (digital input, 24/96 data at 0dBFS)**

Shown above is the fast Fourier transform (FFT) for a 1kHz input sine-wave stimulus, measured at the output across an 8-ohm load at 10W for the coaxial digital input, sampled at 24/96. We find roughly the same signal and noise-related harmonics dominating and at the same levels as seen in the 16/44.1 FFT above.

**FFT spectrum – 1kHz (digital input, 16/44.1 data at -90dBFS)**

Shown above is the FFT for a 1kHz -90dBFS dithered 16/44.1 input sine-wave stimulus at the coaxial digital input, measured at the output across an 8-ohm load. We see the 1kHz primary signal peak, at the correct amplitude, and noise harmonics from the right channel at near and slightly above the signal level.

**FFT spectrum – 1kHz (digital input, 24/96 data at -90dBFS)**

Shown above is the FFT for a 1kHz -90dBFS dithered 24/96 input sine-wave stimulus at the coaxial digital input, measured at the output across an 8-ohm load. We see the 1kHz primary signal peak, at the correct amplitude, and noise harmonics from the right channel at near and slightly above the signal level.

**FFT spectrum – 1kHz (MM phono input)**

Shown above is the FFT for a 1kHz input sine-wave stimulus, measured at the output across an 8-ohm load at 10W for the MM phono input. The second (2kHz), third (3kHz), and fourth (4kHz) signal harmonics from the left channel dominate at around -80dBrA (2kHz), or 0.01%, and -95dBrA (3/4kHz), or 0.002%. On the left side of the main signal peak, we find the fundamental (60Hz) and its odd harmonics (180/300/420Hz) dominating with levels from -75dBrA, or 0.02%, down to -90dBrA, or 0.003%.

**FFT spectrum – 50Hz (line-level input)**

Shown above is the FFT for a 50Hz input sine-wave stimulus measured at the output across an 8-ohm load at 10W for the analog line-level input. The X axis is zoomed in from 40Hz to 1kHz, so that peaks from noise artifacts can be directly compared against peaks from the harmonics of the signal. The second (100Hz) signal harmonic dominates at -85dBrA, or 0.006%. We also see the odd 60Hz power-supply related harmonics at -90/80dBrA (left/right), or 0.003/0.01%, and below. Also evident are IMD product between the signal and noise harmonic peaks.

**FFT spectrum – 50Hz (MM phono input)**

Shown above is the FFT for a 50Hz input sine-wave stimulus measured at the output across an 8-ohm load at 10W for the MM phono input. The X axis is zoomed in from 40Hz to 1kHz, so that peaks from noise artifacts can be directly compared against peaks from the harmonics of the signal. The most predominant (non-signal) peak is from the 60Hz power-supply fundamental at -75dBrA, or 0.02%. The second (100Hz) signal harmonic peak is below this level at around -85dBrA, or 0.006%.

**Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, line-level input)**

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sine-wave stimulus tone measured at the output across an 8-ohm load at 10W for the analog line-level input. The input RMS values are set at -6.02dBrA so that, if summed for a mean frequency of 18.5kHz, would yield 10W (0dBrA) into 8 ohms at the output. We find that the second-order modulation product (*i.e.*, the difference signal of 1kHz) is just above (left) and below (right) -90dBrA, or 0.003%. The third-order modulation products, at 17kHz and 20kHz, are lower at around -100dBrA, or 0.001%.

**Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, coaxial digital input, 16/44.1)**

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sine-wave stimulus tone measured at the output across an 8-ohm load at 10W for the digital coaxial input at 16/44.1. We find that the second-order modulation product (*i.e.*, the difference signal of 1kHz) is just below -90dBrA, or 0.003%. The third-order modulation products, at 17kHz and 20kHz, are lower at just above -100dBrA, or 0.001%. IMD products due to the 44.1kHz sampling frequency are also evident.

**Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, coaxial digital input, 24/96)**

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sine-wave stimulus tone measured at the output across an 8-ohm load at 10W for the digital coaxial input at 24/96. We find that the second-order modulation product (*i.e.*, the difference signal of 1kHz) is just below -90dBrA, or 0.003%. The third-order modulation products, at 17kHz and 20kHz, are lower at just below -100dBrA, or 0.001%.

**Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, MM phono input)**

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sine-wave stimulus tone measured at the output across an 8-ohm load at 10W for the MM phono input. We find that the second-order modulation product (*i.e.*, the difference signal of 1kHz) is right around -80dBrA, or 0.01%. The third-order modulation products, at 17kHz and 20kHz, are around -105dBrA, or 0.0006%.

**Square-wave response (10kHz)**

Above is the 10kHz square-wave response using the analog line-level input, at roughly 10W into 8 ohms. Due to limitations inherent to the Audio Precision APx555 B Series analyzer, this graph should not be used to infer or extrapolate the Attessa’s slew-rate performance. Rather, it should be seen as a qualitative representation of the Attessa’s mid-tier bandwidth. An ideal square wave can be represented as the sum of a sine wave and an infinite series of its odd-order harmonics (*e.g.*, 10kHz + 30kHz + 50kHz + 70kHz . . .). A limited bandwidth will show only the sum of the lower-order harmonics, which may result in noticeable undershoot and/or overshoot, and softening of the edges. While there is no ringing in the corners of the square wave, the edges are softened.

**Damping factor vs. frequency (20Hz to 20kHz)**

The final graph above is the damping factor as a function of frequency. Both channels show a higher damping factor at low frequencies (over 200 at 20Hz), dipping down to just below 100 at 20kHz.

*Diego Estan*

Electronics Measurement Specialist

- Details
- Parent Category: Products
- Category: Amplifier Measurements

Link: reviewed by Dennis Burger on *SoundStage! Access* on September, 2022

**General Information**

All measurements taken using an Audio Precision APx555 B Series analyzer.

The Evo 150 was conditioned for 1 hour at 1/8th full rated power (~18W into 8 ohms) before any measurements were taken. All measurements were taken with both channels driven, using a 120V/20A dedicated circuit, unless otherwise stated.

The Cambridge Audio Evo 150 offers one unbalanced line-level analog input (RCA), one unbalanced moving-magnet (MM) phono input (RCA), one balanced line-level analog input (XLR), one coaxial S/PDIF digital (RCA), two optical S/PDIF digital inputs (TosLink), one USB digital input, an HDMI ARC digital input, an ethernet digital connection for streaming, one pair of analog line-level pre-outs (RCA), one line-level sub-out (RCA), and two sets (A and B) of speaker level outputs. On the front of the unit is a 1/8″ TRS headphone output. For the purposes of these measurements, the following inputs were evaluated: digital coaxial, and the analog line-level (RCA) and MM unbalanced inputs.

Most measurements were made with a standard 2Vrms line-level analog input, 5mVrms MM input, and 0dBFS digital input. For the analog inputs, the tone-control bypass function was enabled. The signal-to-noise ratio (SNR) measurements were made with the same input signal values but with the volume set to achieve the rated output power of 150W (8 ohms). For comparison, on the line-level input, an SNR measurement was also made with the volume at maximum, where only 0.7Vrms was required to achieve 150W into 8ohms.

Based on the accuracy and non-repeatable results at various volume levels of the left/right channel matching (see table below), the Evo 150 volume control is likely operating in the analog domain but with digital control. The volume control offers a total range of 0 to 100 on the display, which measured from -46.2dB (position 1) to +33.9dB between the line-level analog input and the speaker outputs, in increments of 2dB steps below 10, 1dB from 10 to 20, then 0.5dB steps above 20 to 100.

Because the Evo 150 uses switching amplifier technology that exhibits noise above 20kHz (see FFTs below), our typical input bandwidth filter setting of 10Hz-90kHz was necessarily changed to 10Hz-22.4kHz for all measurements, except for frequency response and for FFTs. In addition, THD versus frequency sweeps were limited to 6kHz to adequately capture the second and third signal harmonics with the restricted bandwidth setting.

**Volume-control accuracy (measured at speaker outputs): left-right channel tracking**

Volume position | Channel deviation |

1 | 0.042dB |

10 | 0.069dB |

20 | 0.113dB |

30 | 0.115dB |

40 | 0.044dB |

50 | 0.022dB |

70 | 0.022dB |

90 | 0.028dB |

100 | 0.003dB |

**Published specifications vs. our primary measurements**

The table below summarizes the measurements published by Cambridge Audio for the Evo 150 compared directly against our own. The published specifications are sourced from Cambridge’s website, either directly or from the manual available for download, or a combination thereof. With the exception of frequency response, where the Audio Precision bandwidth was extended from DC to 500kHz, assume, unless otherwise stated, 10W into 8 ohms and a measurement input bandwidth of 10Hz to 22.4kHz, and the worst-case measured result between the left and right channels.

Parameter | Manufacturer | SoundStage! Lab |

Rated output power into 8 ohms (1% THD, 1kHz) | 150W | 152W |

Frequency response (line-level input) | 20Hz-20kHz 0/-3dB | 20Hz-20kHz 0/-0.5dB |

Our primary measurements revealed the following using the line-level analog input and digital coaxial input (unless specified, assume a 1kHz sine wave at 2Vrms or 0dBFS, 10W output, 8-ohm loading, 10Hz to 22.4kHz bandwidth):

Parameter | Left channel | Right channel |

Maximum output power into 8 ohms (1% THD+N, unweighted) | 152W | 152W |

Maximum output power into 4 ohms (1% THD+N, unweighted) | 292W | 292W |

Maximum burst output power (IHF, 8 ohms) | 154.5W | 154.5W |

Maximum burst output power (IHF, 4 ohms) | 292W | 292W |

Continuous dynamic power test (5 minutes, both channels driven) | passed | passed |

Crosstalk, one channel driven (10kHz) | -87.7dB | -102.1dB |

Damping factor | 251 | 229 |

Clipping no-load output voltage | 36.5Vrms | 36.5Vrms |

DC offset | <9.3mV | <-3.1mV |

Gain (pre-out) | 8.15dB | 8.19dB |

Gain (maximum volume) | 33.95dB | 33.94dB |

IMD ratio (CCIF, 18kHz + 19kHz stimulus tones, 1:1) | <-90dB | <-93dB |

IMD ratio (SMPTE, 60Hz + 7kHz stimulus tones, 4:1 ) | <-80dB | <-79dB |

Input impedance (line input, RCA) | 43.8k ohms | 42.9k ohms |

Input impedance (line input, XLR) | 85.2k ohms | 91.7k ohms |

Input sensitivity (for rated power, maximum volume) | 0.7Vrms | 0.7Vrms |

Noise level (A-weighted) | <98uVrms | <116uVrms |

Noise level (unweighted) | <135uVrms | <170uVrms |

Output Impedance (pre-out) | 47.7 ohms | 48.2 ohms |

Signal-to-noise ratio (full rated power, A-weighted, 2Vrms in) | 110.8dB | 109.6dB |

Signal-to-noise ratio (full rated power, unweighted, 2Vrms in) | 108.3dB | 107.1dB |

Signal-to-noise ratio (full rated power, A-weighted, max volume) | 110.9dB | 109.4dB |

Dynamic range (full rated power, A-weighted, digital 24/96) | 110.8dB | 110.2dB |

Dynamic range (full rated power, A-weighted, digital 16/44.1) | 95.3dB | 95.3dB |

THD ratio (unweighted) | <0.0027% | <0.0031% |

THD ratio (unweighted, digital 24/96) | <0.0024% | <0.0027% |

THD ratio (unweighted, digital 16/44.1) | <0.0024% | <0.0027% |

THD+N ratio (A-weighted) | <0.0033% | <0.0038% |

THD+N ratio (A-weighted, digital 24/96) | <0.0030% | <0.0033% |

THD+N ratio (A-weighted, digital 16/44.1) | <0.0034% | <0.0037% |

THD+N ratio (unweighted) | <0.0031% | <0.0036% |

Minimum observed line AC voltage | 119VAC | 119VAC |

For the continuous dynamic power test, the Evo 150 was able to sustain only 216W into 4 ohms (~1% THD) using an 80Hz tone for 500ms, alternating with a signal at -10dB of the peak (13.3W) for 5 seconds, for 5 continuous minutes without the protection circuit shutting down the unit. This test is meant to simulate sporadic dynamic bass peaks in music and movies. During the test, the top of the Evo 150 was slightly warm to the touch. It should be noted that 216W is well below the measured 292W at 1kHz. This is because the Evo 150 exhibits much higher levels of distortion at lower frequencies at high power levels (see THD Versus Frequency Versus Output Power graph below).

Our primary measurements revealed the following using the phono-level input, MM configuration (unless specified, assume a 1kHz 5mVrms sine-wave input, 10W output, 8-ohm loading, 10Hz to 22.4kHz bandwidth):

Parameter | Left channel | Right channel |

Crosstalk, one channel driven (10kHz) | -81.9dB | -83.7dB |

DC offset | <9.8mV | <-3.2mV |

Gain (default phono preamplifier) | 38.9dB | 38.9dB |

IMD ratio (CCIF, 18kHz + 19kHz stimulus tones, 1:1) | <-92dB | <-92dB |

IMD ratio (CCIF, 3kHz + 4kHz stimulus tones, 1:1) | <-92dB | <-90dB |

Input impedance | 52.0k ohms | 53.2k ohms |

Input sensitivity (to max power with max volume) | 8mVrms | 8mVrms |

Noise level (A-weighted) | <270uVrms | <240uVrms |

Noise level (unweighted) | <550uVrms | <480uVrms |

Overload margin (relative 5mVrms input, 1kHz) | 21.6dB | 21.6dB |

Signal-to-noise ratio (full rated power, A-weighted) | 97.5dB | 98.5dB |

Signal-to-noise ratio (full rated power, unweighted) | 92.2dB | 93.1dB |

THD (unweighted) | <0.0014% | <0.0016% |

THD+N (A-weighted) | <0.0035% | <0.0032% |

THD+N (unweighted) | <0.0068% | <0.0057% |

Our primary measurements revealed the following using the analog input at the headphone output (unless specified, assume a 1kHz sine-wave input, 2Vrms output, 300 ohms loading, 10Hz to 90kHz bandwidth):

Parameter | Left channel | Right channel |

Maximum output power into 600 ohms (1% THD+N, unweighted) | 170mW | 170mW |

Maximum output power into 300 ohms (1% THD+N, unweighted) | 323mW | 323mW |

Maximum output power into 32 ohms (1% THD+N, unweighted) | 1.05W | 1.05W |

Gain | 7.73dB | 7.76dB |

Output impedance | 1.2 ohms | 1.4 ohms |

Noise level (A-weighted) | <13uVrms | <22uVrms |

Noise level (unweighted) | <71uVrms | <82uVrms |

Signal-to-noise ratio (A-weighted, ref. max output voltage) | 121.9dB | 122.7dB |

Signal-to-noise ratio (unweighted, ref. max output voltage) | 116.0dB | 116.6dB |

THD ratio (unweighted) | <0.092% | <0.100% |

THD+N ratio (A-weighted) | <0.108% | <0.117% |

THD+N ratio (unweighted) | <0.102% | <0.107% |

Of note in the chart above are the unusually high THD ratios measured at the headphone output at 2Vrms into 300 ohms. This was explored further with a THD vs Measured Output Level sweep (shown below). There is a distinct jump in THD ratios right around the 1Vrms mark, well within the linear range of the amp, and well below the 1% THD mark of nearly 10Vrms. This behavior is unusual, but was repeatable. Into 600 ohms, the THD behavior was similar; however, into a high-impedance load (100k ohms), as well as a low impedance load (32 ohms), this behavior was not seen. We are currently exploring the issue with Cambridge Audio.

**Frequency response (8-ohm loading, line-level input)**

In our measured frequency-response chart above, the Evo 150 is nearly flat within the audioband (20Hz to 20kHz). At the extremes, the Evo 150 is 0dB at 5Hz and -0.5dB at 20kHz. This corroborates Cambridge’s claim of 20Hz-20kHz, 0/-3dB. The -3dB point was measured around 70kHz. In the graph above and most of the graphs below, only a single trace may be visible. This is because the left channel (blue or purple trace) is performing identically to the right channel (red or green trace), and so they perfectly overlap, indicating that the two channels are ideally matched.

**Frequency response (8-ohm loading, line-level input, bass and treble controls)**

Above are frequency-response plots measured at the speaker-level outputs into 8 ohms, with the bass and treble controls set to maximum (blue/red plots) and minimum (purple/green plots). We see that for the bass and treble controls, roughly +/-10dB of gain/cut are available at 20Hz and 20kHz.

**Frequency response (sub-out line-level analog output)**

Above is the frequency response plot measured at the line-level sub output. We see that this output does not implement a useable low-pass filter, but would rely on a device upstream to implement filtering (*e.g.*, control within an active subwoofer). The -3dB point is at roughly 2.5kHz.

**Phase response (8-ohm loading, line-level input)**

Above are the phase response plots from 20Hz to 20kHz for the line level input, measured across the speaker outputs at 10W into 8 ohms. The Evo 150 does not invert polarity and exhibits, at worst, less than 20 degrees (at 20Hz) of phase shift within the audioband.

The chart above shows the Evo 150’s frequency response as a function of input type measured across the speaker outputs at 10W into 8 ohms. The green trace is the same analog input data from the previous graph. The blue trace is for a 16-bit/44.1kHz dithered digital input signal from 5Hz to 22kHz using the coaxial digital input, and the purple trace is for a 24/96 dithered digital input signal from 5Hz to 48kHz, while the pink trace is for a 24/192 dithered digital input signal from 5Hz to 96kHz. The 16/44.1 data exhibits brick-wall-type filtering, with a -3dB point at 20.9kHz. The 24/96 and 24/192 kHz data yielded -3dB points at 44.9kHz and 49.5kHz, respectively. All frequency-response curves are down 0.5dB at roughly 20kHz. The analog input shows more extended response at high frequencies than the 24/192 input. There’s no evidence that the Evo 150 digitizes incoming analog signals.

**Frequency response (8-ohm loading, MM phono input)**

The chart above shows the frequency response for the MM phono input. What is shown is the deviation from the RIAA curve, where the input signal sweep is EQ’d with an inverted RIAA curve supplied by Audio Precision (*i.e.*, zero deviation would yield a flat line at 0dB). We see a maximum deviation of about -1dB at 50Hz and +0.5dB at 300Hz, from 20Hz to 20kHz.

**Phase response (MM input)**

Above is the phase response plot from 20Hz to 20kHz for the MM phono input, measured across the speaker outputs at 10W into 8 ohms. The Evo 150 does not invert polarity. For the phono input, since the RIAA equalization curve must be implemented, which ranges from +19.9dB (20Hz) to -32.6dB (90kHz), phase shift at the output is inevitable. Here we find a worst case of about -60 degrees at 300Hz and 6kHz, and +80 degrees at 20Hz.

**Digital linearity (16/44.1 and 24/96 data)**

The chart above shows the results of a linearity test for the coaxial digital input for both 16/44.1 (blue/red) and 24/96 (purple/green) input data, measured at the line-level pre-outs of the Evo 150 for a 2Vrms (at 0dBFS) output signal. The digital input is swept with a dithered 1kHz input signal from -120dBFS to 0dBFS, and the output is analyzed by the APx555. The ideal response would be a straight flat line at 0dB. Both data were essentially perfect as of -100dBFS up to 0dBFS. At -120dBFS, the 16/44.1 data were about +4/2dB (left/right) above reference, while the 24/96 data were within -1dB of reference. This is a good linearity test result.

**Impulse response (24/44.1 data)**

The graph above shows the impulse response for a looped 24/44.1 test file that moves from digital silence to full 0dBFS (all “1”s) for one sample period then back to digital silence, measured at the line-level pre-outs of the Evo 150. We can see that the Evo 150 DAC utilizes a typical sinc function reconstruction filter.

**J-Test (coaxial)**

The chart above shows the results of the J-Test test for the coaxial digital input measured at the line-level pre-outs of the Evo 150. The J-test was developed by Julian Dunn in the 1990s. It is a test signal—specifically a -3dBFS undithered 12kHz square wave sampled (in this case) at 48kHz (24 bits). Since even the first odd harmonic (*i.e.*, 36kHz) of the 12kHz square wave is removed by the bandwidth limitation of the sampling rate, we are left with a 12kHz sine wave (the main peak). In addition, an undithered 250Hz squarewave at -144dBFS is mixed with the signal. This test file causes the 22 least significant bits to constantly toggle, which produces strong jitter spectral components at the 250Hz rate and its odd harmonics. The test file shows how susceptible the DAC and delivery interface are to jitter, which would manifest as peaks above the noise floor at 500Hz intervals (*e.g.*, 250Hz, 750Hz, 1250Hz, etc.). Note that the alternating peaks are in the test file itself, but at levels of -144dBrA and below. The test file can also be used in conjunction with artificially injected sine-wave jitter by the Audio Precision, to show how well the DAC rejects jitter.

The coaxial input (the optical input behaved identically) exhibits a few low-level peaks in the left channel at low frequencies within the audioband, at -120dBrA and below. This is a good J-test result, indicating that the Evo 150 DAC likely has good jitter immunity.

**J-Test with 500ns of injected jitter (coaxial)**

Both the coaxial and optical inputs were also tested for jitter immunity by injecting artificial sine-wave jitter at 2kHz, which would manifest as sidebands at 10kHz and 14kHz without any jitter rejection. Jitter immunity proved excellent, with visible sidebands at only -125dBrA despite a very high 500ns of jitter level.

**Wideband FFT spectrum of white noise and 19.1kHz sine-wave tone (coaxial input, Filter 1)**

The plot above shows a fast Fourier transform (FFT) of the Evo 150’s line-level pre-outs with white noise at -4dBFS (blue/red) and a 19.1 kHz sine wave at 0dBFS (1Vrms) fed to the coaxial digital input, sampled at 16/44.1. The sharp roll-off above 20kHz in the white-noise spectrum shows the implementation of a brick-wall type reconstruction filter. There are no aliased image peaks in the audioband above the -130dBrA noise floor. The main 25kHz alias peak is at -115dBrA. The second, third, and fourth distortion harmonics (38.2, 57.3, 76.4kHz) are at -100dBrA and below. Here again, like in the J-Test result, the left channel is exhibiting low-level (-120dBrA and below) peaks at low frequencies within the audioband in the 19.1kHz sinewave FFT.

**RMS level vs. frequency vs. load impedance (1W, left channel only)**

The chart above shows RMS level (relative to 0dBrA, which is 1W into 8ohms or 2.83Vrms) as a function of frequency, for the analog line-level input swept from 5Hz to 100kHz. The blue plot is into an 8-ohm load, the purple is into a 4-ohm load, the pink plot is an actual speaker (Focal Chora 806, measurements can be found here), and the cyan plot is no load connected. The chart below . . .

. . . is the same but zoomed in to highlight differences. Here we can see a maximum deviation within the audioband of about 0.1dB from 4 ohms to no load, which is an indication of a relatively high damping factor, or low output impedance. The maximum variation in RMS level when a real speaker was used is even less, deviating by about 0.05dB within the flat portion of the curve (20Hz to 10kHz). Note that the dip in RMS level at higher frequencies is a result of the frequency response of the Evo 150, and not a damping factor issue, as all four plots show the same dip, at roughly the same rate.

**THD ratio (unweighted) vs. frequency vs. output power**

The chart above shows THD ratios at the output into 8 ohms as a function of frequency for a sine-wave stimulus at the analog line-level input. The blue and red plots are for the left and right channels at 1W output into 8 ohms, purple/green at 10W, and pink/orange at 124W. The power was varied using the volume control. The Evo 150 manages to maintain consistently flat THD ratios from 20Hz to 6kHz at both 1W and 10W, hovering around 0.002-0.003%. At 124W, THD ratios were much higher, at around 0.3-0.4% from 20 to 100Hz, then a steady decline down to nearly 0.003% at 5kHz.

**THD ratio (unweighted) vs. frequency at 10W (MM phono input)**

The chart above shows THD ratios as a function of frequency plots for the MM phono input measured across an 8-ohm load at 10W. The input sweep is EQ’d with an inverted RIAA curve. The THD values for the MM configuration vary from around 0.005% (20/30Hz) down to 0.001% (5kHz).

**THD ratio (unweighted) vs. output power at 1kHz into 4 and 8 ohms**

The chart above shows THD ratios measured at the output of the Evo 150 as a function of output power for the analog line-level input, for an 8-ohm load (blue/red for left/right channels) and a 4-ohm load (purple/green for left/right channels). Both 8- and 4-ohm data sets track fairly closely, with THD ratios from about 0.002% down to as low as 0.0005% (8-ohm at 0.5W) and 0.007% (4-ohm at 1W). The “knee” for the 8-ohm data is roughly at 120W and nearly 0.01% THD. The 4-ohm data “knee” is just shy of 200W, but at a lower 0.002% THD. The 1% THD values are reached at about 152W (8-ohm) and 292W (4-ohm).

**THD+N ratio (unweighted) vs. output power at 1kHz into 4 and 8 ohms**

The chart above shows THD+N ratios measured at the output of the Evo 150 as a function of output power for the line-level input, for an 8-ohm load (blue/red for left/right channels) and a 4-ohm load (purple/green for left/right channels). Overall, THD+N values for both loads were similar but slightly lower for the 8-ohm load, ranging from about 0.01%, down to 0.002%.

**THD ratio (unweighted) vs. frequency at 8, 4, and 2 ohms (left channel only)**

The chart above shows THD ratios measured at the output of the Evo 150 as a function of frequency into three different loads (8/4/2 ohms) for a constant input voltage that yields 10W at the output into 8 ohms (and roughly 20W into 4 ohms, and 40W into 2 ohms) for the analog line-level input. The 8-ohm load is the blue trace, the 4-ohm load the purple trace, and the 2-ohm load the pink trace. We find nearly identical THD ratios, from 0.005% to roughly 0.002% across all three loads—an exceptional result, which showcases how impervious the Evo 150 is to even very low speaker impedances.

**THD ratio (unweighted) vs. frequency into 8 ohms and real speakers (left channel only)**

The chart above shows THD ratios measured at the output of the Evo 150 as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). Above 50Hz or so, all three plots show similar THD ratios from 0.005% to about 0.002%. At very low frequencies, THD ratios were the highest with the two-way speaker, measuring 0.05% at 20Hz, over 20dB higher than the 0.002% measured acoss the dummy load. This again showacses that across most of the audioband, the Evo 150 is mostly impervious to speaker-load variations.

**IMD ratio (CCIF) vs. frequency into 8 ohms and real speakers (left channel only)**

The chart above shows intermodulation distortion (IMD) ratios measured at the output of the Evo 150 as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. Here the CCIF IMD method is used, where the primary frequency is swept from 20kHz (F1) down to 2.5kHz, and the secondary frequency (F2) is always 1kHz lower than the primary, with a 1:1 ratio. The CCIF IMD analysis results are the sum of the second (F1-F2, or 1kHz) and third modulation products (F1+1kHz, or F2-1kHz). The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a two-way speaker (Paradigm Founder Series 100F, measurements can be found here). All three results are very similar, with relatively constant IMD ratios between 0.002% to 0.003%. This is an excellent result.

**IMD ratio (SMPTE) vs. frequency into 8 ohms and real speakers (left channel only)**

The chart above shows IMD ratios measured at the output of the Evo 150 as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. Here, the SMPTE IMD method is used, where the primary frequency (F1) is swept from 250Hz down to 40Hz, and the secondary frequency (F2) is held at 7kHz with a 4:1 ratio. The SMPTE IMD analysis results consider the second (F2 ± F1) through the fifth (F2 ± 4xF1) modulation products. The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). All three results are nearly identical, with flat IMD results just below 0.01%.

**FFT spectrum – 1kHz (line-level input)**

Shown above is the fast Fourier transform (FFT) for a 1kHz input sine-wave stimulus, measured at the output across an 8-ohm load at 10W for the analog line-level input. We find the third signal harmonic (3kHz) dominating at -90dBrA, or 0.003%, compared to the other signal harmonics which are below -110dBrA, or 0.0003%. On the left side of the main signal peak, we find the odd harmonics (180/300/420Hz) of the power-supply fundamental dominating with levels around -105dBrA, or 0.0006%, for the right channel, and -115dBrA, or 0.0002%, for the left channel.

**FFT spectrum – 1kHz (digital input, 16/44.1 data at 0dBFS)**

Shown above is the fast Fourier transform (FFT) for a 1kHz input sine-wave stimulus, measured at the output across an 8-ohm load at 10W for the coaxial digital input, sampled at 16/44.1. We find the same signal- and noise-related harmonics dominating and at the same levels as seen in the analog FFT above.

**FFT spectrum – 1kHz (digital input, 24/96 data at 0dBFS)**

Shown above is the fast Fourier transform (FFT) for a 1kHz input sine-wave stimulus, measured at the output across an 8-ohm load at 10W for the coaxial digital input, sampled at 24/96. We find the same signal- and noise-related harmonics dominating and at the same levels as seen in the 16/44.1 FFT above, but with a lower noise floor due to the 24-bit depth.

**FFT spectrum – 1kHz (digital input, 16/44.1 data at -90dBFS)**

Shown above is the FFT for a 1kHz -90dBFS dithered 16/44.1 input sine-wave stimulus at the coaxial digital input, measured at the output across an 8-ohm load. We see the 1kHz primary signal peak, at the correct amplitude, and noise harmonics between -100dBrA, or 0.001%, and -140dBrA, or 0.00001%. The noise floor of the left channel (blue) is slightly better throughout the audioband, though the noise floor of the right channel (red) is still commendably low.

**FFT spectrum – 1kHz (digital input, 24/96 data at -90dBFS)**

Shown above is the FFT for a 1kHz -90dBFS dithered 24/96 input sine-wave stimulus at the coaxial digital input, measured at the output across an 8-ohm load. We see the 1kHz primary signal peak, at the correct amplitude, and noise harmonics between -100dBrA, or 0.001%, and -140dBrA, or 0.00001%. Once again, the noise floor of the left channel (blue) is lower than that of the right channel (red), though not above about 6kHz.

**FFT spectrum – 1kHz (MM phono input)**

Shown above is the FFT for a 1kHz input sine-wave stimulus, measured at the output across an 8-ohm load at 10W for the MM phono input. The second (2kHz) and third (3kHz) signal harmonics dominate at around -100dBrA, or 0.001%. On the left side of the main signal peak, we find the odd harmonics (180/300/420Hz) of the power-supply fundamental dominating with levels from -90dBrA, or 0.003%, down to -100dBrA, or 0.001%. This is a clean, low-noise MM phono FFT for an integrated amplifier.

**FFT spectrum – 50Hz (line-level input)**

Shown above is the FFT for a 50Hz input sine-wave stimulus measured at the output across an 8-ohm load at 10W for the analog line-level input. The X axis is zoomed in from 40Hz to 1kHz, so that peaks from noise artifacts can be directly compared against peaks from the harmonics of the signal. The second (100Hz) and third (150Hz) signal harmonics dominate at -100dBrA, or 0.001%, and -90dBrA, or 0.003%, respectively. We also see the odd 60Hz power-supply related harmonics at -105dBrA, or 0.0006%, and below.

**FFT spectrum – 50Hz (MM phono input)**

Shown above is the FFT for a 50Hz input sine-wave stimulus measured at the output across an 8-ohm load at 10W for the MM phono input. The X axis is zoomed in from 40Hz to 1kHz, so that peaks from noise artifacts can be directly compared against peaks from the harmonics of the signal. The most predominant (non-signal) peak is from the 60Hz power-supply third harmonic (180Hz) at -90dBrA, or 0.003%. The second-order (100Hz) and third-order (150Hz) signal harmonic peaks are below this level at around -100dBrA, or 0.001%.

**Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, line-level input)**

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sine-wave stimulus tone measured at the output across an 8-ohm load at 10W for the analog line-level input. The input RMS values are set at -6.02dBrA so that, if summed for a mean frequency of 18.5kHz, would yield 10W (0dBrA) into 8 ohms at the output. We find that the second-order modulation product (*i.e.*, the difference signal of 1kHz) is just below -100dBrA, or 0.001%. The third-order modulation products, at 17kHz and 20kHz are around -105dBrA, or 0.0006%.

**Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, coaxial digital input, 16/44.1)**

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sine-wave stimulus tone measured at the output across an 8-ohm load at 10W for the digital coaxial input at 16/44.1. We find that the second-order modulation product (*i.e.*, the difference signal of 1kHz) is just below -100dBrA, or 0.001%. The third-order modulation products, at 17kHz and 20kHz, are at around the same level.

**Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, coaxial digital input, 24/96)**

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sine-wave stimulus tone measured at the output across an 8-ohm load at 10W for the digital coaxial input at 24/96. The FFT spectrum is nearly identical within the audioband to the 16/44.1 FFT above, except for the lower noise floor due to the increased bit depth.

**Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, MM phono input)**

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sine-wave stimulus tone measured at the output across an 8-ohm load at 10W for the MM phono input. We find that the second-order modulation product (*i.e.*, the difference signal of 1kHz) is right around -100dBrA, or 0.001%. The third-order modulation products, at 17kHz and 20kHz, are around -105dBrA, or 0.0006%.

**Square-wave response (10kHz)**

Above is the 10kHz square-wave response using the analog line-level input, at roughly 10W into 8 ohms. Due to limitations inherent to the Audio Precision APx555 B Series analyzer, this graph should not be used to infer or extrapolate the Evo 150’s slew-rate performance. Rather, it should be seen as a qualitative representation of the Evo 150’s extended bandwidth for a switching amplifier. An ideal square wave can be represented as the sum of a sine wave and an infinite series of its odd-order harmonics (*e.g.*, 10kHz + 30kHz + 50kHz + 70kHz . . .). A limited bandwidth will show only the sum of the lower-order harmonics, which may result in noticeable undershoot and/or overshoot, and softening of the edges. Here we can see the 400kHz switching oscillator frequency used in the digital amplifier section clearly visible modulating the waveform.

**Square-wave response (10kHz)**

Above is the 10kHz square-wave response using the analog input, at roughly 10W into 8 ohms, with a 250kHz restricted bandwidth to remove the modulation from the 400kHz oscillator. We can see a relatively clean square-wave reproduction for a switching amplifier.

**FFT spectrum of 400kHz switching frequency relative to a 1kHz tone**

The Evo 150’s class-D amplifier relies on a switching oscillator to convert the input signal to a pulse-width-modulated (PWM) square wave (on/off) signal before sending the signal through a low-pass filter to generate an output signal. The Evo 150 oscillator switches at a rate of about 400kHz, and this graph plots a wide-bandwidth FFT spectrum of the amplifier’s output at 10W into 8 ohms as it’s fed a 1kHz sine wave. We can see that the 400kHz peak is quite evident, and at -35dBrA. There is also a peak at 800kHz and 1200kHz, (the second and third harmonic of the 400kHz peak), at -65/-75dBrA. Those three peaks—the fundamental and its second and third harmonics—are direct results of the switching oscillators in the Evo 150 amp modules. The noise around those very-high-frequency signals are in the signal, but all that noise is far above the audioband—and therefore inaudible—and so high in frequency that any loudspeaker the amplifier is driving should filter it all out anyway.

**Damping factor vs. frequency (20Hz to 20kHz)**

The final graph above is the damping factor as a function of frequency. Both channels show a relatively constant and high damping factor of 230 (right) and 250 (left) from 20Hz to around 7kHz, then a small rise to 250 (right) and 300 (left) at 20kHz.

*Diego Estan*

Electronics Measurement Specialist

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