Details

Parent Category: Products

Category: Headphone Amplifier Measurements

Created: 01 October 2018

Reviewed on: SoundStage! Solo, October 2018

I measured the iFi Audio xDSD using a Clio 10 FW audio analyzer and a Neutrik NL-1 Minilyzer. For all of these tests, I used the xDSD’s coaxial digital input. Note that this is the first DAC-headphone amp I’ve measured for SoundStage! Solo; I’ve decided to focus my efforts on tests that confirm such devices’ basic functionality, and that gauge the efficacy of any special features and functions that might be measurable.

This chart shows the xDSD’s frequency response in its Listen and Measure modes, and with XBass+ engaged, with a 24-bit/192kHz S/PDIF signal and the xDSD set for 1mW output into a 32-ohm load. The response in both modes measured -0.16dB at 20Hz and -0.26dB at 20kHz. Listen mode actually measured slightly better here, with less rolloff above 65kHz; apparently, the switch is mislabeled. The bass boost in XBass+ mode was 6.48dB at 20Hz.

This chart shows the xDSD’s frequency response in Listen and Measure modes, and with XBass+ engaged, with a 16/48 S/PDIF signal and the xDSD set for 1mW output into a 32-ohm load. The treble response at 20kHz in Measure mode is -1.91dB, and in Listen mode -0.32dB. Definitely, the switch is mislabeled. According to the xDSD manual, the Listen filter is “transient-optimized minimum phase” and the Measure filter is “frequency response optimized,” but a filter with -1.91dB rolloff at 20kHz is certainly not “frequency response optimized.”

This chart shows the output of the xDSD vs. its total harmonic distortion (THD) into loads of 32, 250, and 600 ohms. Although iFi specifies the xDSD’s power output into 16, 50, 300, and 600 ohms, which renders most of my measurements not directly comparable, those measurements do suggest that iFi’s specs are on the mark. The xDSD’s output into 32 ohms is 291mW at 0.5% THD and 304mW at 1% THD; into 250 ohms, the output is 53mW at 0.5% THD and 54mW at 1% THD; and into 600 ohms, the xDSD puts out 22mW at 0.5% THD and 23mW at 1% THD.

Here you can see the xDSD’s spectrum of harmonic distortion and noise floor when driven by a 24/192 S/PDIF signal and referenced to 1.5V RMS output at 600Hz. Note that the distortion profile of the Measure and Listen modes is effectively the same.

I measured the xDSD’s output impedance as 0.8 ohm at 1kHz, which confirms iFi’s rating of <1 ohm. I prefer a headphone amp’s output impedance to be 1 ohm or less; the output impedance will then not react significantly with the reactance of the headphones, and thus won’t affect the ’phones’ frequency response.

. . . Brent Butterworth
brentb@soundstagenetwork.com

Details

Parent Category: Products

Category: Amplifier Measurements

Created: 15 January 2026

Link: reviewed by Jason Thorpe on SoundStage! Ultra on January 15, 2026

General information

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

The D‑80 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 D‑80 is a two-channel amplifier with two balanced (XLR) inputs and three pairs of speaker level outputs: 4-, 8-, and 16-ohm taps. Unless otherwise stated, the 8-ohm taps were used for these measurements. An input of 520mVrms was required to achieve the reference 10W into 8 ohms.

Our typical input bandwidth filter setting of 10Hz-22.4kHz was used for all measurements except FFTs and THD versus frequency, where a bandwidth of 10Hz-90kHz was used. Frequency response measurements utilize a DC-to-1 MHz input bandwidth.

Published specifications vs. our primary measurements

The table below summarizes the measurements published by Audio Research for the D‑80 compared directly against our own. The published specifications are sourced from Audio Research’s website, either directly or from the manual available for download, or a combination thereof. Assume, unless otherwise stated, 10W into 8 ohms and a measurement input bandwidth of 10Hz to 22.4kHz. Our primary measurements revealed the following (unless specified, assume a 1kHz sinewave at 520mVrms at the input, 10W output, 8-ohm loading, 10Hz to 22.4kHz bandwidth):

Our primary measurements revealed the following using the balanced line-level analog input (unless specified, assume a 1kHz sinewave at 520mVrms, 10W output, 8-ohm loading, 10Hz to 22.4kHz bandwidth):

For the continuous dynamic power test, the D‑80 was able to sustain about 81W into 4 ohms (~3% THD) using an 80Hz tone for 500ms, alternating with a signal at -10dB of the peak (8.1W) 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 sides and top of the D‑80 were very hot to the touch.

Frequency response (8-ohm loading)

In our frequency-response (relative to 1kHz) plot above, measured across the speaker outputs at 10W into 8 ohms, the D‑80 exhibits a near-flat frequency response across the audioband (0/-0.25dB at 20Hz/20kHz). At 5Hz the D‑80 is at roughly -3dB, and the high frequency -3dB point is at 70kHz.

Phase response (8-ohm loading)

Above is the phase-response plot from 20Hz to 20kHz for the balanced line-level input, measured across the speaker outputs at 10W into 8 ohms. The D‑80 does not invert polarity and exhibits, at worst, only -20 degrees of phase shift at 20kHz.

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 10Hz 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 maximum deviation between a 4-ohm load and no load to be around 2.2dB through most of the audioband. At 20kHz, the deviation is about 2.5dB. This is an indication of a very low damping factor, or high output impedance, endemic of most tube amplifiers. With a real speaker, the deviations from 20Hz to 20kHz were lower, but still within the potentially audible range, at roughly 1.6dB.

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 plot is at 1W output into 8 ohms, purple at 10W, and pink is at the maximum achievable power (67W). THD ratios increase as power is increased. At 1W, THD ranges from 0.02% at lower frequencies to 0.1% at 20kHz. At 10W, we find THD ratios between 0.15% and 0.7% at 20kHz. And at 67W, THD ratios exceed 1%, ranging from about 1.5% to 5%.

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

The chart above shows THD ratios measured at the output of the D‑80 as a function of output power for the analog line-level input for an 8-ohm load (blue/red) and a 4-ohm load (purple/green), for the 8-ohm taps. The 8-ohm data ranged from 0.005% at 50mW, steadily increasing to 1% at the maximum power output of 67W. Increasing the input voltage beyond this point only serves to increase THD while maintaining the same 67W. The 4-ohm data ranged from 0.015% at 50mW, steadily increasing to 2% at the maximum power output of 84W. Increasing the input voltage beyond this point only serves to increase THD while maintaining the same 84W.

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

The chart above shows THD+N ratios measured at the output of the D‑80 as a function of output power for the analog line level-input, for an 8-ohm load (blue/red) and a 4-ohm load (purple/green), for the 8-ohm taps. The 8-ohm data ranged from 0.02% at 50mW, steadily increasing to 1% at the maximum power output of 67W. Increasing the input voltage beyond this point only serves to increase THD+N while maintaining the same 67W. The 4-ohm data ranged from 0.015% at 50mW, steadily increasing to 2% at the maximum power output of 84W. Increasing the input voltage beyond this point only serves to increase THD+N while maintaining the same 84W.

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

The chart above shows THD ratios measured at the output of the D‑80 as a function of output power for the analog line-level input for an 8-ohm load (blue/red) and a 4-ohm load (purple/green), for the 4-ohm taps. The 8-ohm data ranged from 0.005% at 50mW, steadily increasing to roughly 1.5% at the maximum power output of just past 40W. Increasing the input voltage beyond this point only serves to increase THD while maintaining the same power. The 4-ohm data ranged from 0.02% at 50mW, steadily increasing to 1.5% at the maximum power output of just past 60W. Increasing the input voltage beyond this point only serves to increase THD while maintaining the same power.

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

The chart above shows THD+N ratios measured at the output of the D‑80 as a function of output power for the analog line level-input, for an 8-ohm load (blue/red) and a 4-ohm load (purple/green), for the 4-ohm taps. The 8-ohm data ranged from 0.02% at 50mW, steadily increasing to roughly 1.5% at the maximum power output of just past 40W. Increasing the input voltage beyond this point only serves to increase THD+N while maintaining the same power. The 4-ohm data ranged from 0.03% at 50mW, steadily increasing to 1.5% at the maximum power output of just past 60W. Increasing the input voltage beyond this point only serves to increase THD+N while maintaining the same power.

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 D‑80 as a function of frequency into three different loads (8/4/2 ohms) for a constant input voltage that yields roughly 10W at the output into 8 ohms (blue), 20W into 4 ohms (purple), and 40W into 2 ohms (pink). The 8-ohm data ranged from 0.1-0.2% between 20Hz and 4kHz, then up to 0.7% at 20kHz. The 4-ohm THD data ranged from 0.5% from 20Hz to 200Hz, then steadily up to 2.5% at 20kHz. The 2-ohm data yielded THD ratios from 2% at 20Hz up to 8% at 20kHz. This shows that the D‑80 is stable into 2-ohms, but will exhibit very high THD ratios.

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 D‑80 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 very low frequencies, the two-way speaker yielded the highest THD ratios (2%). In the all-important 300Hz to 5kHz range, THD ratios into all three loads were close, with the data into real speakers hovering above and below (+/-10dB) the 0.02-0.03% values seen for the resistive load. At the highest frequencies, the three-way speaker yielded the highest THD ratios (0.2% at 20kHz).

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 D‑80 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 IMD results into the resistive load are fairly consistent, from 0.03 to 0.05% across the sweep. The results were lower and higher for the real speakers, ranging from 0.02% to 0.07%.

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 D‑80 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). The IMD results into the resistive load remained constant at 0.1% across the weep. The results were lower and higher for the real speakers, ranging from 0.05% to nearly 0.2%.

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 balanced analog line-level input. We see that the signal’s second (2kHz), third (3kHz), and fifth (5kHz) harmonics dominate at -60dBrA (2/3kHz) and -70dBrA (5kHz), or 0.1% and 0.03%. Other signal harmonics can be seen from -90dBrA (0.003%) to below -120dBrA (0.0001%). There are power-supply noise-related harmonics throughout the FFT, at -100dBrA, or 0.001%, and below.

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 balanced 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 again the signal’s second (100Hz), third (150Hz), and fifth (250Hz) harmonics at -60dBrA (100/150kHz) and -70dBrA (250Hz), or 0.1% and 0.03%. There are power-supply noise-related harmonics throughout the FFT, at -100dBrA, or 0.001%, and below.

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 balanced analog line-level input. The input RMS values were 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 the -65dBrA (0.2%) level, while the third-order modulation products, at 17kHz and 20kHz, are at the same level.

Intermodulation distortion FFT (line-level input, APx 32 tone)

Shown above is the FFT of the speaker-level output of the D‑80 with the APx 32-tone signal applied to the input. The combined amplitude of the 32 tones is the 0dBrA reference, and corresponds to 10W into 8 ohms. The intermodulation products—i.e., the “grass” between the test tones—are distortion products from the amplifier and are at the -90dBrA, or 0.003%, level.

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 D‑80’s slew-rate performance. Rather, it should be seen as a qualitative representation of the D‑80’s relatively wide 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. In this case, we see a reasonably clean result, with mild ringing in the plateaus.

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

The final graph above is the damping factor as a function of frequency. We find very low damping-factor values, from 6-7 from 20Hz to 2kHz. This is a very poor damping factor result, but typical for tube amps.

Diego Estan
Electronics Measurement Specialist

Details

Parent Category: Products

Category: Amplifier Measurements

Created: 01 January 2026

Link: reviewed by Roger Kanno on SoundStage! Simplifi on January 1, 2026

General Information

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

The Line Majik DSM 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 Majik DSM offers two line-level analog inputs (RCA), moving-magnet (MC) and moving-coil (MC) phono inputs (RCA), two digital S/PDIF inputs (RCA coaxial and TosLink optical), and other network connections for streaming. In terms of outputs, there are line-level subwoofer and pre-outs (RCA), and a pair of speaker level outputs. Also included is a ¼″ TRS headphone output on the front panel. For the purposes of these measurements, the following inputs were evaluated: coaxial digital (RCA) and the analog line-level and phono MM and MC (RCA) inputs.

Most measurements were made with a 2Vrms line-level analog input or 0dBFS digital input. The signal-to-noise (SNR) measurements were made with the same input signal values but with the volume set to achieve the output power of 74W (into 8 ohms) for 1% THD. For comparison, on the analog input, a SNR measurement was also made with the volume at maximum, but with a lower input signal to achieve the same 74W.

Based on the accuracy and repeatability at various volume levels of the left/right channel matching (see table below), the Majik DSM volume control is operating in the digital domain. Consequently, all analog signals are digitized (sampled at 24/192) at the Majik DSM’s inputs so the unit may apply volume and EQ functions. The volume control offers a total range from -65dB to +34dB (line-level inputs, speaker level outputs) using 100 increments of 1dB.

Because the Majik DSM 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

Published specifications vs. our primary measurements

The table below summarizes the measurements published by Linn for the Majik DSM compared directly against our own. The published specifications are sourced from Linn’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 1MHz, 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.

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):

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

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):

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

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

In our frequency response plots above (relative to 1kHz), measured across the speaker outputs at 10W into 8 ohms, the Majik DSM is near flat within the audioband (20Hz to 20kHz, 0/-0.2dB). The -3dB point is at roughly 55kHz, with sharp high-frequency attenuation. Due to either noise or excessive DC leakage, we could not measure the Majik DSM without a low-pass filter (10Hz) on the analyzer’s inputs. This is why the plot is limited to 10Hz (and not 5Hz). 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 perfectly overlap, indicating that the two channels are ideally matched.

Frequency response (8-ohm loading, line-level input with subwoofer output)

The chart above shows the frequency response (relative to 1kHz) measured across the speaker outputs at 10W into 8 ohms, as well as the line-level sub-out frequency response (relative to 20Hz). The subwoofer was engaged in the settings for these measurements, with the cut-off frequency set to 80Hz. The Bass Redirect setting was engaged, which applies a low-pass second order filter to the line-level sub-outs, and a mirror high-pass filter to the main speaker outputs. We see that both traces merge at 80Hz at -6dB, as expected.

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 Majik DSM digitizes all incoming analog signals at 24/192, subsequently, true phase delay will be significant as it includes the timing delay associated with the ADC process. Here we see roughly -500000 degrees at 20kHz. Below, is . . .

. . . a phase plot that only shows the excess phase (timing delays removed). Here we see +20 degrees at 20Hz (which should be ignored because the low-pass filter on the analyzer inputs had to be engaged), and +40 degrees at 20kHz.

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

The chart above shows the frequency response (relative to 1kHz) 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 very flat response from 20Hz to 3kHz (indicative of RIAA EQ applied in the digital domain), followed by a steep rise in response (+1dB at 20kHz), peaking at 45kHz (+4dB).

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

The chart above shows the frequency response for the MC phono input. We see a very flat response across the audioband (0dB at 20Hz, -0.2dB at 20kHz).

Phase response (8-ohm loading, MM input, excess)

Above is the excess phase response plot from 20Hz to 20kHz for the MM phono input, measured across the speaker outputs at 10W into 8 ohms. The Majik DSM 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 +100 degrees at 20Hz and -5 degrees at 6-8kHz.

Phase response (8-ohm loading, MC input, excess)

Above is the excess phase response plot from 20Hz to 20kHz for the MC phono input, measured across the speaker outputs at 10W into 8 ohms. We find the same result as with the MM input above.

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

The chart above shows the Majik DSM’s frequency response (relative to 1kHz) as a function of input type measured across the speaker outputs at 10W into 8 ohms. The two green traces are the same analog input data from the speaker-level frequency-response graph above. The blue and red traces are for a 16-bit/44.1kHz dithered digital input signal from 5Hz to 22kHz using the coaxial input, the purple and green traces are for a 24/96 dithered digital input signal from 5Hz to 48kHz, and the pink and orange traces are for a 24/192 dithered digital input signal. The -3dB points are roughly: 21kHz for the 16/44.1 data, 40kHz for the 24/96, and 55kHz for the 24/192 data. The analog plots follow the 24/192 plots as expected, because analog signals are sampled at 24/192.

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-outputs of the Majik DSM, where 0dBFS was set to yield 1Vrms. For this test, 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. The 24/96 data were at +1dB at -120dBFS, while the 16/44.1 data were +2/3dB at -120dBFS.

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 Majik DSM. We find a typical symmetrical sinc-function 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 pre-outputs of the Majik DSM where 0dBFS is set to 1Vrms. 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 (24bit). 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.

Here we see a relatively strong J-Ttest result. While several peaks can be seen in the audioband, they are very low in amplitude and range from -135dBFS down to -150dBFS. This is an indication that the Majik DSM DAC may have strong 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-outputs of the Majik DSM. The optical input yielded essentially the same results compared to the coaxial input.

J-Test (coaxial, 100ns jitter)

The chart above shows the results of the J-Test test for the coaxial digital input measured at the line-level output of the Majik DSM, with an additional 100ns of 2kHz sinewave jitter injected by the APx555. The telltale peaks at 10kHz and 12kHz cannot be seen, indicating strong jitter rejection. The optical input yielded the same result.

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 Majik DSM’s line-level pre-outputs with white noise at -4dBFS (blue/red) and a 19.1 kHz 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 brickwall-type filtering. There are no low-level aliased image peaks within the audioband. The primary aliasing signal at 25kHz is highly suppressed at -140dBrA, while the second and third distortion harmonics (38.2, 57.3kHz) of the 19.1kHz signal are at -105 and -120dBFS.

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 10Hz to 50kHz. 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 see that the deviations between no load and 4 ohms are roughly 0.2dB. With a real speaker load, deviations measured lower, at roughly 0.1dB. At frequencies above 3-4kHz, there appears to be some sort of active compensation occurring at the outputs (the no load and 4-ohm load plots cross over at 6kHz, which would imply a negative output impedance).

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

The chart above shows THD ratios at the speaker-level outputs 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 the left and right channels at 1W output into 8 ohms, purple/green at 10W, and pink/orange at 65W. The power was varied using the Majik DSM’s volume control. The 1W THD ratios were the lowest, ranging from 0.0005% from 20Hz to 1kHz, then up to 0.002% at 20kHz. The 10W THD ratios were slightly higher ranging from 0.0005% to 0.004%. At 65W, THD ratios ranged from 0.0005% at lower frequencies, up to roughly 0.005-0.01% from 150Hz to 20kHz.

THD ratio (unweighted) vs. frequency at 10W (phono input, MM and MC)

The chart above shows THD ratios as a function of frequency plots for the MM (blue/red) and MC (purple/green) phono inputs measured across an 8-ohm load at 10W. For this test, the input sweep was EQ’d with an inverted RIAA curve. The THD values for the MM configuration vary from around 0.03% (20Hz) down to 0.002% (2/3kHz left channel), then up to 0.005% at 20kHz. The THD values for the MC configuration vary from around 0.01% (20Hz) down to 0.002% (2/3kHz), then up to 0.005% at 20kHz. It should be noted that often the limiting factor in THD measurements for phono inputs is the higher noise floor. The analyzer cannot assign a THD ratio for a signal harmonic peak it cannot see above the noise floor, and therefore the THD ratio is assigned the value of the noise floor relative to the signal.

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

The chart above shows THD ratios measured at the speaker-level outputs of the Majik DSM as a function of output power for the analog line-level input for an 8-ohm load (blue/red for left/right) and a 4-ohm load (purple/green for left/right), with the volume set to maximum. THD ratios into 4 and 8 ohms are close (with 3-4dB below 10W). For the 8-ohm load, they range from 0.015% at 50mW, down to just above 0.001% in the 10 to 50W range. The “knee” into 8 ohms can be found just past 55W, with the 1% THD mark hit at 74W. For the 4-ohm load, THD ratios range from 0.02% at 50mW, down to 0.002% at 10W, then up to 0.003% up to the “knee,” just past 100W, with the 1% THD mark hit at 136W.

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

The chart above shows THD+N ratios measured at the speaker-level outputs of the Majik DSM as a function of output power for the analog line-level input for an 8-ohm load (blue/red for left/right) and a 4-ohm load (purple/green for left/right). THD+N ratios into 4 and 8 ohms are close (with 3-4dB). They range from 0.1-0.2% at 50mW, down to 0.005-0.006% at 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 Majik DSM 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 and the 4-ohm load the purple trace. We find a roughly 5-10dB increase in THD from 8 to 4 to 2 ohms. These ranged from 0.0005% from 20Hz to 300Hz, then up to 0.004% at 20kHz for the 8-ohm load. The 4-ohm load ranged from 0.0006% at 20-30Hz up to 0.005% at 20kHz. The 2-ohm load ranged from 0.001% at 20Hz up to 0.006% from 1-3kHz, then up to 0.008% 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 Majik DSM 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 thee-way speaker (Paradigm Founder Series 100F, measurements can be found here). Generally, THD ratios into the real speakers were much higher than those measured across the resistive dummy load, from 20Hz to 1kHz. The differences ranged from 0.1% at 20Hz for the two-way speaker (0.01% for the three-way speaker) versus 0.0005% for the resistive load, and 0.004% at 20kHz into the three-way speaker versus 0.002% for the resistive load. Between 1kHz and 3kHz, all three THD traces were very close, around the 0.0006-0.0007% 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 Majik DSM 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). We find that all three IMD traces are close to one another, ranging from 0.001-0.002% at 2.5kHz, up to a peak of 0.05% at around 15kHz.

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 Majik 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 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). We find very similar IMD ratios into all three loads; a flat 0.003% across the sweep.

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 (2kHz) and third (3kHz) harmonics dominate at a -110/-105dBrA, or 0.0003/0.0006%. There are subsequent signal harmonics visible at and below the -120dBrA, or 0.0001%, level. On the right side of the signal peak, we find no power-supply-related noise peaks above the -130 to -140dBrA noise floor. We also see a rise in the noise floor above 20kHz, characteristic of class-D amps.

FFT spectrum – 1kHz (MM phono 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 phono MM input. We see that the signal’s second (2kHz) and third (3kHz) harmonics dominate at a -110/-105dBrA, or 0.0003/0.0006%, the same as with the line-level FFT above. On the right side of the signal peak, we find two main power-supply-related noise peaks: the primary (60Hz) at -80dBrA, or 0.01%, and the third harmonic (180Hz) at -85dBrA, or 0.006%.

FFT spectrum – 1kHz (MC phono 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 phono MC input. We see that the signal’s second (2kHz) harmonic can be seen amongst the power-supply-related noise peaks at -100dBrA, or 0.001%. On the right side of the signal peak, we find the two most significant main power-supply related noise peaks at 60Hz (-60dBrA, or 0.1%) and 180Hz (-65dBrA, or 0.06%). A multitude of subsequent power-supply-related noise harmonics can be seen at and below -80dBrA, or 0.01%.

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. We see that the signal’s second (2kHz) and third (3kHz) harmonics dominate at a -110/-105dBrA, or 0.0003/0.0006%.  Subsequent harmonics can be seen at and below the -120dBrA, or 0.0001%, level. No visible power-supply-related noise peaks can be seen above the -135dBrA noise floor.

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. We see essentially the same result as with the 16/44.1 FFT above, but with a lower noise floor due to the increased bid 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, with the second (2kHz) signal harmonic just barely noticeable above the -135dBrA noise floor.

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 between -120 and -140dBrA (0.0001-0.00001%).

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 most predominant (non-signal) peak is the second (100Hz) signal harmonic at -100dBrA, or 0.001%. Other signal harmonics peaks can be seen at -110dBrA 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 the 60Hz fundamental power-supply noise peak and its third (180Hz) harmonic at -80/-85dBrA, or 0.01/0.006%. The highest signal harmonic peak is at 100Hz, at -90dBrA, or 0.003%.  

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 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 the 60Hz fundamental power-supply noise peak and its third (180Hz) harmonic at -60/-65dBrA, or 0.1/0.06%. The highest signal harmonic is at 100Hz, at -70dBrA, or 0.03%.

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. For this test, 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 -120dBrA, or 0.0001%, while the third-order modulation products, at 17kHz and 20kHz, are at the -95dBrA, or 0.002%, level.

Intermodulation distortion FFT (line-level input, APx 32 tone)

Shown above is the FFT of the speaker-level output of the Majik DSM with the APx 32-tone signal applied to the analog input. The combined amplitude of the 32 tones is the 0dBrA reference and corresponds to 10W into 8 ohms. The intermodulation products—i.e., the “grass” between the test tones—are distortion products from the amplifier and are at and below the -125dBrA level.

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

Shown above is an FFT of the intermodulation distoriton (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 (-1dBFS). We find that the second-order modulation product (i.e., the difference signal of 1kHz) is at -120dBrA, or 0.0001%, while the third-order modulation products, at 17kHz and 20kHz, are at the -95dBrA, or 0.002%, 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 (-1dBFS).We find that the second-order modulation product (i.e., the difference signal of 1kHz) is at -120dBrA, or 0.0001%, while the third-order modulation products, at 17kHz and 20kHz, are at the -95dBrA, or 0.002%, 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 -100dBrA, or 0.001%, while the third-order modulation products, at 17kHz and 20kHz, are at -90dBrA, or 0.003%.

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%, while the third-order modulation products, at 17kHz and 20kHz, are at -95dBrA, or 0.002%.

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 Majik DSM’s slew-rate performance. Rather, it should be seen as a qualitative representation of the Majik DSM’s mid-tier 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. In this case, we find very soft/rounded corners, and the 600kHz oscillator modulating the square wave.

Squarewave response (1kHz)

Above is the 1kHz squarewave response using the analog line-level input, with a 250kHz bandwidth restriction on the analyzer’s inputs to filter out the 600kHz oscillator. Here we see a relatively clean response with some overshoot and ringing in the corners.

FFT spectrum of 400kHz switching frequency relative to a 1kHz tone

The Majik DSM’s 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 Majik DSM 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 -35dBrA. There is also a peak at 1.2MHz (the second harmonic of the 600kHz peak), at -70dBrA. Those three peaks—the fundamental and its second harmonic—are direct results of the switching oscillators in the Majik DSM 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. We can see here a constant damping factor of between 100 and 200 up to 2kHz. Beyond this point, there appears to be some sort of active compensation occurring at the outputs (a negative output impedance was measured, which is not possible).

Diego Estan
Electronics Measurement Specialist

Details

Parent Category: Products

Category: Amplifier Measurements

Created: 01 November 2025

Link: reviewed by Jason Thorpe on SoundStage! Ultra on November 1, 2025

General Information

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

The VinnieRoss Brama 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 Brama offers five pairs of line-level balanced analog inputs (XLR only), one pair of left/right fixed line-level outputs (XLR), and two sets of speaker-level outputs. The Brama has three gain settings (low/medium/high at 22/28/34dB), unless otherwise stated, the medium setting was used.

Most measurements were made with a 2Vrms line-level analog input. The signal-to-noise (SNR) measurements were made with the default input signal values but with the volume set to achieve the achievable output power of 200W into 8 ohms. For comparison, an SNR measurement was also made with the volume at maximum.

Based on the accuracy and randomness of the left/right volume channel matching (see table below), the Brama volume control is operating in the analog domain. The Brama overall volume range is from -32dB to +27dB (balanced line-level input, speaker output).

Our typical input bandwidth filter setting of 10Hz-22.4kHz was used for all measurements except FFTs and THD versus frequency, where a bandwidth of 10Hz-90kHz was used. Frequency response measurements utilize a DC to 1MHz input bandwidth.

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

Published specifications vs. our primary measurements

The table below summarizes the measurements published by VinnieRossi for the Brama compared directly against our own. The published specifications are sourced from VinnieRossi’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 1MHz, 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.

Our primary measurements revealed the following using the line-level analog input (unless specified, assume a 1kHz sinewave at 2Vrms):

For the continuous dynamic power test, the Brama was able to sustain 483W into 4 ohms (~3% THD) using an 80Hz tone for 500ms, alternating with a signal at -10dB of the peak (31W) for 5 seconds, for 247 seconds of the 5 continuous minute before the fault protection circuit engaged due to excessive heat. This test is meant to simulate sporadic dynamic bass peaks in music and movies.

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

In our frequency response plots above (relative to 1kHz), measured across the speaker outputs at 10W into 8 ohms, the Brama is essentially flat within the audi band, and at -3dB right around 200kHz. The Brama appears to be AC coupled, yielding roughly -2.5dB at 5Hz. 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 Brama appears to invert polarity (relative to the pin2/3 –  +/- XLR standard), but only yielded +15 degrees of shift at 20Hz, and -15 degrees at 20kHz.

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 see that the deviations between no load and 4 ohms are small at roughly 0.08dB. With a real speaker load, deviations were smaller, at roughly 0.06dB.

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

The chart above shows THD ratios at the speaker-level outputs 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 the left and right channels at 1W output into 8 ohms, purple/green at 10W, and pink/orange at 198W (just shy of the rated output of 200W). The power was varied using the Brama’s volume control. All data are fairly closely lumped together and tell the story of the Brama’s THD performance across most all of our measurements; THD results are dominated and limited by the implementation of a tube per channel in the preamp section. Due to this implementation, varying the conditions at the speaker outputs of the Brama (which utilize transistors) does very little to change the measured THD ratios. Here, we find consistent THD ratios around 0.2% at all frequencies and power levels.

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

The chart above shows THD ratios measured at the speaker-level outputs of the Brama as a function of output power for the analog line-level input, for an 8-ohm load (blue/red for left/right) and a 4-ohm load (purple/green for left/right), with the volume set to maximum. THD ratios into 4 and 8 ohms are close (within roughly 5dB). For the 8-ohm load, THD ratios ranged from 0.005% at 50mW, up to 0.15% at the “knee” at roughly 230W, then up to the 1% THD mark at 255W. For the 4-ohm load, THD ratios ranged from 0.01% at 50mW, up to 0.15% at the “knee” at roughly 420W, then up to the 1% THD mark at 451W.

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

The chart above shows THD+N ratios measured at the speaker-level outputs of the Brama as a function of output power for the analog line-level input, for an 8-ohm load (blue/red for left/right) and a 4-ohm load (purple/green for left/right). THD+N ratios into 4 and 8 ohms are close (within 3-5dB). THD+N ratios range from roughly 0.05% (50 mW) to 0.15% at 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 Brama as a function of frequency into three different loads (8/4/2 ohms) for a constant input voltage that yields 50W at the output into 8 ohms (and roughly 100W into 4 ohms, and 200W 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. Once again, THD ratios are the same due to the tube in the preamp section, hovering at 0.15-0.2% across the sweep. The 2-ohm data stop at 500Hz due to the protection circuit, which presumably engaged due to excessive heat.

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 Brama 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). Again, all THD ratios are all roughly the same, near the 0.2% 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 Brama 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). We find that all three IMD traces are essentially the same, again due to the limitations of tube-use in the preamp, and hover around 0.15% across the sweep.

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 Brama 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). We find identical IMD results for all three loads, at 0.4% from 40Hz to 500Hz, then down to 0.006%.

FFT spectrum – 1kHz (XLR line-level input, medium gain)

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 balanced input. We see significant signal harmonic peaks up to the limits of the FFT (90kHz), ranging from the highest at 2kHz (-55dBrA, or 0.2%) down to the -130dBrA, or 0.00003%, level. Once again, the high THD results are from the use of the tube in each channel of the preamp section. On the right side of the signal peak, we find power-supply-related noise peaks at 60/180/300 Hz, but at relatively low levels. The 60Hz peak dominates at -120/–110dBrA (left/right), or 0.0001%/0.0003%. The other peaks are below -120dBrA, or 0.0001%. This FFT can be characterized as high THD, but relatively low noise.

FFT spectrum – 1kHz (XLR line-level input, low gain)

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 balanced input, with the gain set to low and the volume adjusted to achieve the same output. We see essentially the same FFT as with the gain set to medium above.

FFT spectrum – 1kHz (XLR line-level input, high gain)

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 balanced input, with the gain set to high and the volume adjusted to achieve the same output. We see essentially the same FFT as with the gain set to medium above.

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 most predominant (non-signal) peak is the second (100Hz) signal harmonic at -55dBrA, or 0.2%, and subsequent signal harmonics can be seen down to the -120dBrA, or 0.0001%, level. Power-supply-related noise peaks are the same as the 1kHz FFT above, with the 60Hz peak dominating at -120/–110dBrA (left/right), or 0.0001%/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 -60dBrA, or 0.1%, while the third-order modulation products, at 17kHz and 20kHz, are at roughly the -70dBrA, or 0.03%, level.

Intermodulation distortion FFT (line-level input, APx 32 tone)

Shown above is the FFT of the speaker-level output of the Brama with the APx 32-tone signal applied to the analog input. The combined amplitude of the 32 tones is the 0dBrA reference, and corresponds to 10W into 8 ohms. The intermodulation products—i.e., the “grass” between the test tones—are distortion products from the amplifier and are at and below the  -90dBrA, or 0.003%, level.

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 Brama’s slew-rate performance. Rather, it should be seen as a qualitative representation of the Brama’s high 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. In this case, we find very clean corners with no over/undershoot.

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

The final graph above is the damping factor as a function of frequency. Both channels track very closely. We can see damping factors of roughly 200 across the entire 20Hz to 20kHz band.

Diego Estan
Electronics Measurement Specialist

Details

Parent Category: Products

Category: Amplifier Measurements

Created: 01 October 2025

Link: reviewed by Philip Beaudette on SoundStage! Hi-Fi on October 1, 2025

General information

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

The MCA 225 Gen 2 was conditioned for 1 hour at 1/8th full rated power (~28W 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 MCA 225 Gen 2 is a two-channel amplifier with a set of balanced (XLR) and unbalanced (RCA) inputs, and one set of speaker level outputs. An input of 320mVrms was required to achieve the reference 10W into 8 ohms. There were no appreciable differences observed (THD, noise, gain) between the XLR and RCA inputs, however, comparative FFTs are provided in this report. Unless otherwise stated, the XLR inputs were used for all measurements.

Our typical input bandwidth filter setting of 10Hz-22.4kHz was used for all measurements except FFTs and THD versus frequency where a bandwidth of 10Hz-90kHz was used. Frequency response measurements utilize a DC to 1 MHz input bandwidth.

Published specifications vs. our primary measurements

The table below summarizes the measurements published by Anthem for the MCA 225 Gen 2 compared directly against our own. The published specifications are sourced from Anthem’s website, either directly or from the manual available for download, or a combination thereof. Assume, unless otherwise stated, 10W into 8 ohms and a measurement input bandwidth of 10Hz to 22.4kHz:

Our primary measurements revealed the following (unless specified, assume a 1kHz sinewave at 305mVrms at the input, 10W output, 8-ohm loading, 10Hz to 22.4kHz bandwidth):

For the continuous dynamic power test, the MCA 225 Gen 2 was able to sustain about 360W into 4 ohms (~3% THD) using an 80Hz tone for 500ms, alternating with a signal at -10dB of the peak (36W) for 5 second, 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 sides and top of the MCA 225 Gen 2 were warm to the touch.

Frequency response (8-ohm loading)

In our frequency response (relative to 1kHz) plot above, measured across the speaker outputs at 10W into 8 ohms, the MCA 225 Gen 2 exhibits an essentially perfectly flat frequency response across the audioband (0/0dB at 20Hz/20kHz). The MCA 225 Gen 2 is only about 0.1dB down at 5Hz. In the higher frequencies, the -3dB point is at roughly 90kHz. 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)

Above is the phase response plot from 20Hz to 20kHz for the balanced line-level input, measured across the speaker outputs at 10W into 8 ohms. The MCA 225 Gen 2 does not invert polarity and exhibits at worst -20 degrees of phase shift at 20kHz.

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 10Hz 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 maximum deviation between a 4-ohm load and no-load to be around 0.04dB up to 3kHz. Beyond 3kHz, the deviations are as high as 0.32dB at 20kHz. This is an indication of a very high damping factor, or low output impedance. With a real speaker, the maximum deviations from 20Hz to 20kHz were roughly 0.06dB.

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 at 1W output into 8 ohms, purple and green at 10W, and pink and orange at 200W. The 10W data yielded the lowest THD results, from just below 0.0002% from 20Hz to 500Hz, then a rise to 0.01% at 20kHz. The 1W data ranged from 0.0005% from 20Hz to 2kHz, then a rise to 0.01% at 20kHz. The 200W data ranged from 0.0006% from 30Hz to 1kHz, then up to 0.015% (left) and 0.1% (right) 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 MCA 225 Gen 2 as a function of output power for the analog line-level input for an 8-ohm load (blue/red) and a 4-ohm load (purple/green). The 8-ohm data ranged from 0.002% at 50mW, down to 0.0003% from 5 to 20W, then up to 0.0007% at the “knee,” at roughly 190W. The 4-ohm data ranged from 0.003% at 50mW, down to 0.0005% from 10 to 100W, then up to 0.0008% at the “knee,” at roughly 300W. The 1% THD marks were reached at 210W and 336W into 8 and 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 MCA 225 Gen 2 as a function of output power for the analog line-level input, for an 8-ohm load (blue/red) and a 4-ohm load (purple/green). The 8-ohm data ranged from 0.02% at 50mW, down to a low of 0.0007% from 50-100W, then up to the “knee.” The 4-ohm data ranged from 0.03% at 50mW, down to a low of 0.0008% from 100-200W, then up to the “knee.”

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 MCA 225 Gen 2 as a function of frequency into three different loads (8/4/2 ohms) for a constant input voltage that yields roughly 50W at the output into 8 ohms (blue), 100W into 4 ohms (purple), and 200W into 2 ohms (pink). The 8-ohm data ranged from 0.0003% from 20Hz to 300Hz, then up to 0.01% at 20kHz. The 4-ohm THD data ranged from 0.0007% from 20Hz to 1kHz, then up to 0.02% at 20kHz. The 2-ohm data ranged from 0.0003% from 20Hz to 100Hz, then up to 0.03% at 20kHz. This shows that the MCA 225 Gen 2 is perfectly stable into 2-ohm loads, with low THD ratios even at 200W.

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 MCA 225 Gen 2 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 very low frequencies, the two-way speaker yielded the highest THD ratios (0.02%), compared to 0.002% for the three-way speaker and 0.0003% of the resistive load. In the all-important 300Hz to 5kHz range, THD ratios into the real speakers were between 5dB higher and 5dB lower than the resistive load, hovering between the 0.0004-0.0007% level. At the highest frequencies, the three-way speaker yielded the highest THD ratios (0.02% at 20kHz).

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 MCA 225 Gen 2 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 IMD results into the resistive load range from 0.0006% up to 0.004% across the sweep. The results were similar for the two-way speaker but higher for the three-way speaker (0.002% to 0.015%).

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 MCA 225 Gen 2 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 2-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a 3-way speaker (Paradigm Founder Series 100F, measurements can be found here).  All three plots are essentially identical and constant at 0.005%.

FFT spectrum – 1kHz (XLR 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 balanced analog line-level input. We see that the signal’s second (2kHz) and third (3kHz) harmonics dominate at just below -110dBrA, or 0.0003%. Other signal harmonics can be seen but at -120dBrA to -130dBrA, or 0.0001% to 0.00003%. There are only four visible power-supply noise-related harmonics, but these are below the -120dBrA level, or 0.0001%. This is a clean FFT result.

FFT spectrum – 1kHz (RCA 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 unbalanced analog line-level input. The main differences between this and the balanced line-level FFT above are a lower second (2kHz) signal harmonic at -120dBrA, or 0.0001%, and a lower overall noise floor (-150dBrA vs -140dBrA), which subsequently shows a multitude of power-supply noise-related peaks around the -140dBrA level, or 0.00001%.

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 balanced 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 signal’s second (100Hz) harmonic and the power-supply noise-related peak at 120Hz. Both are just below -120dBrA, or 0.0001%.

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 balanced 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 products (i.e., the difference signal of 1kHz) are just above -120dBrA, or 0.0001%, while the third-order modulation products, at 17kHz and 20kHz, are higher at -100dBrA, or 0.001%.

Intermodulation distortion FFT (line-level input, APx 32 tone)

Shown above is the FFT of the speaker-level output of the MCA 225 Gen 2 with the APx 32-tone signal applied to the input. The combined amplitude of the 32 tones is the 0dBrA reference, and corresponds to 10W into 8 ohms. The intermodulation products—i.e., the “grass” between the test tones—are distortion products from the amplifier and are below the very low -125dBrA, or 0.00006%, level.

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 MCA 225 Gen 2’s slew-rate performance. Rather, it should be seen as a qualitative representation of the MCA 225 Gen 2’s mid-tier 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. In this case, we see a relatively clean result, with some obvious softening in the corners.

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

The final graph above is the damping factor as a function of frequency. We find very high damping factor values, around 500 from 20Hz to 2kHz. Above 2kHz, there is a dip in the damping factor, reaching roughly 80 at 20kHz.

Diego Estan
Electronics Measurement Specialist

Details

Parent Category: Products

Category: Amplifier Measurements

Created: 01 September 2025

Link: reviewed by Roger Kanno on SoundStage! Hi-Fi on September 1, 2025

General Information

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

The Cambridge Audio EXA100 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 EXA100 offers four sets of line-level analog inputs (three over RCA, one selectable XLR or RCA), one digital coaxial input (RCA), two digital optical inputs (TosLink), one USB digital input, left/right pre-outs (RCA), one sub-out (RCA), two sets of speaker level outputs (A and B), and one headphone output over 1/8″ TRS connector. A Bluetooth input is also offered. For the purposes of these measurements, the following inputs were evaluated: digital coaxial, analog line-level (XLR), and the headphone output.

Most measurements were made with a 2Vrms line-level analog input and 0dBFS digital input. The signal-to-noise ratio (SNR) measurements were made with the default input signal values but with the volume set to achieve the achievable output power of 100W into 8 ohms. For comparison, on the line-level input, a SNR measurement was also made with the volume at maximum.

Based on the accuracy and randomness of the left/right volume channel matching (see table below), the EXA100 volume control is probably a potentiometer operating in the analog domain. The EXA100 overall volume range is from -66dB to +31dB (line-level XLR input, speaker output).

Our typical input bandwidth filter setting of 10Hz–22.4kHz was used for all measurements except FFTs and THD versus frequency, where a bandwidth of 10Hz–90kHz was used. Frequency response measurements utilize a DC to 1MHz input bandwidth.

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

Published specifications vs. our primary measurements

The table below summarizes the measurements published by Cambridge Audio for the EXA100 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 to 1MHz, 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.

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):

For the continuous dynamic power test, the EXA100 was able to sustain 185W into 4 ohms (~3% THD) using an 80Hz tone for 500ms, alternating with a signal at -10dB of the peak (16.1W) for 5 seconds, for 200 seconds of the 500-second test before inducing the fault-protection circuit. This test is meant to simulate sporadic dynamic bass peaks in music and movies. During the test, the top of the EXA100 was slightly warm to the touch.

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

* Default is 2Vrms out into 300 ohms

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

In our frequency-response plots above (relative to 1kHz), measured across the speaker outputs at 10W into 8 ohms, the EXA100 is essentially perfectly flat within the audioband (20Hz to 20kHz, 0/0dB). The -3dB point is at roughly 100kHz, and 0dB at 5Hz. The EXA100 appears to be DC coupled. 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 (line-level subwoofer output)

Above is the frequency response plot (relative to 20Hz) measured at the line-level RCA subwoofer output. The response is flat down to 5Hz, and the -3dB point is at roughly 2.2kHz. External low-pass filtering would need to be applied to this subwoofer output since it extends quite high in frequency.

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 EXA100 does not invert polarity and yielded only about -20 degrees of phase shift at 20kHz.

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

The chart above shows the EXA100’s frequency response (relative to 1kHz) as a function of input type measured across the speaker outputs at 10W into 8 ohms. The two green traces are the same analog input data from the speaker-level frequency-response graph above. The blue and red traces are for a 16-bit/44.1kHz dithered digital input signal from 5Hz to 22kHz using the coaxial input, the purple and green traces are for a 24/96 dithered digital input signal from 5Hz to 48kHz, and the pink and orange traces are for a 24/192 dithered digital input signal. At low frequencies, the digital signals yielded a flat response down to 5Hz, same as the analog response. The -3dB points are: 21kHz for the 16/44.1 data, 46kHz for the 24/96, 79kHz for the 24/192 data, and 100kHz for the analog input.

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-outputs of the EXA100, where 0dBFS was set to yield 2Vrms. For this test, the digital input was swept with a dithered 1kHz input signal from -120dBFS to 0dBFS, and the output was 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. The 24/96 data remain perfect at -120dBFS, while the 16/44.1 data were +3dB at -120 to -110dBFS. In order to investigate the 24/96 performance further, we extended . . .

. . . the sweep down to -140dBFS, where the 24é96 data only overshot the mark by +4dB. This is a solid 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 EXA100. We see a typical symmetrical sinc function response.

J-Test (coaxial input)

The chart above shows the results of the J-Test test for the coaxial digital input measured at the line-level pre-outputs of the EXA100 where 0dBFS is set to 2Vrms. 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.

Here we see high frequency peaks in the spectrum from about 14kHz to 18kHz, reaching about -120dBrA. This noise is also seen in the analog and digital FFTs below, and is not related to jitter in DAC. Ignoring this noise, we see a strong J-Test result, with a single spurious peak at 8kHz at a vanishingly low -140dBrA. This is an indication that the EXA100 DAC should have strong jitter immunity.

J-Test (optical input)

The chart above shows the results of the J-Test test for the optical digital input measured at the line-level pre-outputs of the EXA100. The optical input yielded essentially the same result as the coax input.

J-Test (coaxial input, jitter 100ns)

The chart above shows the results of the J-Test test for the coaxial digital input measured at the line-level output of the EXA100, with an additional 100ns of 2kHz sinewave jitter injected by the APx555. The telltale peaks at 10kHz and 12kHz can be seen but at a very low -140dBFS. This is further evidence of the EXA100 DAC’s strong jitter immunity.

J-Test (optical input, jitter 100ns)

The chart above shows the results of the J-Test test for the optical digital input measured at the line-level output of the EXA100, with an additional 100ns of 2kHz sinewave jitter injected by the APx555. The optical input yielded essentially the same result as the coax input.

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 EXA100’s line-level pre-outputs with white noise at -4dBFS (blue/red) and a 19.1 kHz 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 a filter of the brickwall-type variety. There are no low-level aliased image peaks within the audioband—only the same 14-18kHz noise can be seen that is evident in every FFT for the EXA100. The primary aliasing signal at 25kHz is highly suppressed at -115dBrA, while the second and third distortion harmonics (38.2, 57.3kHz) of the 19.1kHz tone are around -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 50kHz. 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 see that the deviations between no load and 4 ohms are very small at roughly 0.08dB. This is a strong result and an indication of a low output impedance, or high damping factor. With a real speaker load, deviations measured lower at roughly 0.06dB.

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

The chart above shows THD ratios at the speaker-level outputs 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 the left and right channels at 1W output into 8 ohms, purple/green at 10W, and pink/orange at 95W, near the rated power output. The power was varied using the EXA100’s volume control. Between 20Hz and 1kHz, all THD ratios were similar, very low and between 0.0002% and 0.001%. From 1kHz to 20kHz, the 1W data yielded the lowest THD ratios, topping out at 0.002% at 20kHz, then the 10W data at 0.003%, followed by the 95W data at 0.01%.

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

The chart above shows THD ratios measured at the speaker-level outputs of the EXA100 as a function of output power for the analog line-level input for an 8-ohm load (blue/red for left/right) and a 4-ohm load (purple/green for left/right), with the volume at maximum. THD ratios into 4 and 8 ohms are close (within 2-3dB) up to 1-2W. Beyond 10W, the 4-ohm THD data were up to 10dB higher than the 8-ohm data. Into 8 ohms, THD ratios range from 0.004% at 50mW, down to 0.0005% in the 5 to 100W range. The “knee” into 8 ohms can be found right around the rated output power of 100W, while the 4-ohm knee can be seen around 150W. The 1% THD marks were hit at 118W and 180W into 8 and 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 speaker-level outputs of the EXA100 as a function of output power for the analog line level-input, for an 8-ohm load (blue/red for left/right) and a 4-ohm load (purple/green for left/right). THD+N ratios into 4 and 8 ohms are close (with 2-5dB). They range from 0.03% at 50mW, down to 0.001% in the 60 to 100W range.

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 EXA100 as a function of frequency into three different loads (8/4/2 ohms) for a constant input voltage that yielded 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 find a roughly 5-10dB increase in THD from 8 to 4 ohms across the audioband. The 8-ohm data ranged from 0.0005% at 20Hz down to 0.0003% from 50Hz to 500Hz, then up to 0.003% at 20kHz for the 8-ohm load. The 4-ohm load ranged from 0.001% at 20Hz down to 0.0005% from 50-100Hz, then up to 0.007% at 10-15kHz. The 2-ohm THD fared worse, ranging from 0.002% from 20Hz to 60Hz, up to 0.05% at roughly 15kHz.

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 EXA100 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). Generally, THD ratios into the real speakers were higher than those measured across the resistive dummy load. The differences ranged from 0.05% at 20Hz for the two-way speaker versus 0.0008% for the resistive load, and 0.01% at 20kHz into the 3-way speaker versus 0.002% for the resistive load. Between the important frequencies of 500Hz to 6kHz, all three THD traces were very close, around the 0.0003-0.0005% 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 EXA100 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). We find that all three IMD traces are close to one another, with the three-way speaker yielding 5dB higher results in the 4-8kHz range. Most of the IMD results are hovering around the 0.0005-0.001% level.

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 EXA100 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). We find very similar IMD ratios into all three loads, at a constant 0.003%.

FFT spectrum – 1kHz (line-level input, XLR)

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 balanced analog line-level input. We see that the signal’s second (2kHz), third (3kHz), fifth (5kHz), and seventh (7kHz) harmonics dominate between -110dBrA and -120dBrA, or 0.0003% and 0.0001%. The noise peaks discussed earlier in this report, between 14kHz and 18kHz, can also be seen, peaking at -115dBrA, or 0.0002%. On the right side of the signal peak, we only find two very low-level power-supply-related noise peaks, at 180Hz and 300Hz, just below -130dBrA, or 0.00003%.

FFT spectrum – 1kHz (line-level input, RCA)

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 unbalanced analog line-level input. The main difference here compared to the balanced input FFT above is the third (3kHz) signal harmonic, at nearly -100dBrA, or 0.001%, instead of the -110dBrA level for the balanced input.

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 harmonic peaks are essentially the same as with the unbalanced 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. We see essentially the same result as with the 16/44.1 FFT above, but with a lower noise floor due to the increased 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, with no signal harmonics above the -135dBrA noise floor.

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, no signal related harmonic peaks, and power-supply-related noise peaks at a very low -130dBrA, or 0.00003%, and below.

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 most predominant (non-signal) peak is the third (150Hz) signal harmonic at a low -115dBrA, or 0.0002%. Other peaks (both signal harmonics and power-supply noise-related harmonics) can be seen at -120dBrA, or 0.0001%, and below.

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 -110dBRa, or 0.0003%, while the third-order modulation products, at 17kHz and 20kHz are roughly at the same level. This is a very clean IMD result.

Intermodulation distortion FFT (line-level input, APx 32 tone)

Shown above is the FFT of the speaker-level output of the EXA100 with the APx 32-tone signal applied to the analog input. The combined amplitude of the 32 tones is the 0dBrA reference, and corresponds to 10W into 8 ohms. The intermodulation products—i.e., the “grass” between the test tones—are distortion products from the amplifier and are at and below the very low -13odBrA, or 0.00003%, level.

Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, digital 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 (-1dBFS). We find that the second-order modulation product (i.e., the difference signal of 1kHz) is at -105dBrA, or 0.0006%, while the third-order modulation products, at 17kHz and 20kHz, are very low at -110dBrA, or 0.0003%.

Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, digital 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 (-1dBFS). We find that the second-order modulation product (i.e., the difference signal of 1kHz) is at -105dBrA, or 0.0006%, while the third-order modulation products, at 17kHz and 20kHz, are very low at -110dBrA, or 0.0003%.

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 EXA100’s slew-rate performance. Rather, it should be seen as a qualitative representation of the EXA100’s mid-to-high 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. In this case, we find relatively clean corners, with some mild softening and no overshoot.

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

The final graph above is the damping factor as a function of frequency. We can see here a constant damping factor just over 200 through most of the audioband (until about 6kHz). This is a strong result for a medium-powered solid-state integrated amplifier.

Diego Estan
Electronics Measurement Specialist

Details

Parent Category: Products

Category: Amplifier Measurements

Created: 01 September 2025

Link: reviewed by AJ Wykes on SoundStage! Simplifi on September 1, 2025

General Information

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

The Eversolo Play was conditioned for 1 hour at 1/8th full rated power (~8W 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 Play offers two analog inputs (line level and phono configurable MM or MC, both over RCA), two digital S/PDIF inputs (RCA coaxial and TosLink optical), an HDMI input, an ethernet connection for streaming, line-level subwoofer outs (RCA), and a pair of speakerlevel outputs. For the purposes of these measurements, the following inputs were evaluated: coaxial digital (RCA), analog line-level, and phono MM and MC.

Most measurements were made with a 2Vrms line-level analog input, 0dBFS digital input, and 8.5/1.6mVrms for the MM/MC phono configurations (this yielded 10W into 8 ohms with volume at maximum). The signal-to-noise (SNR) measurements were made with the same input signal values but with the volume set to achieve the rated output power of 60W (in this case, the 60W was achieved with the volume at maximum with both 2Vrms and 0dBFS in).

Based on the accuracy and repeatability at various volume levels of the left/right channel matching (see table below), the Play volume control is likely operating in the digital domain. Consequently, all analog signals are digitized at the Play’s inputs so the unit may apply volume and bass management. The volume control offers a total range from -79dB to +20.9dB (speaker-level outputs) in 0.5dB increments, from -99.5dB to 0dB.

Because the Play 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

Published specifications vs. our primary measurements

The table below summarizes the measurements published by Eversolo for the Play compared directly against our own. The published specifications are sourced from Eversolo’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 set at its maximum (10Hz to 1MHz), assume, unless otherwise stated, a measurement input bandwidth of 10Hz to 22.4kHz and the worst-case measured result between the left and right channels.

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

* limited by clipping of the analog-to-digital converter (ADC)
** above this continuous power level, protection circuit may engage

For the continuous dynamic power test, the Play was able to sustain 132W (1% THD) into 4 ohms using an 80Hz tone for 500ms, alternating with a signal at -10dB of the peak (13.2W) 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 Play stayed relatively cool to the touch.

Our primary measurements revealed the following using the analog phono (MM configuration) input (unless specified, assume a 1kHz sinewave at 8.5mVrms, 10W output, 8-ohm loading, 10Hz to 22.4kHz bandwidth):

Our primary measurements revealed the following using the analog phono (MC configuration) input (unless specified, assume a 1kHz sinewave at 1.6mVrms, 10W output, 8-ohm loading, 10Hz to 22.4kHz bandwidth):

* max achievable at 1% THD

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

In our measured frequency-response (relative to 1kHz) chart above, the Play is nearly flat within the audioband (20Hz to 20kHz). At the extremes, the Play is 0.25dB down at 20Hz and 0.4dB up at 20kHz. The -3dB point is just shy of 60kHz with steep attenuation due to the digitization and anti-aliasing filter applied at the analog input, because internally, the Play only processes digital signals. 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 is the phase-response plot from 20Hz to 20kHz for the analog input. The Play does not invert polarity, but due to the sampling by the ADC and the inherent delays associated with this process, the overall phase shift is significant at 1 million degrees at 20kHz.

Frequency response (8-ohm loading, line-level analog input with bass management on)

Above is the frequency-response plot with bass management applied (80Hz cut-off frequency). The purple/green plots are at the speaker-level outputs and relative to 1kHz, blue is the sub-out relative to 20Hz. The cross-over value is at the correct frequency, and the attenuation slope appears to be 18dB/octave.

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

The chart above shows the frequency response (relative to 1kHz) for the phono input (MM configuration). 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 very relatively flat response from 20Hz to 20kHz: 0dB at 20Hz, +0.3dB at 100Hz, +0.5dB at 20kHz.

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

The chart above shows the frequency response (relative to 1kHz) for the phono input (MC configuration). We see essentially the same frequency response as with the MM configuration. Since the input impedance did not change when measured between MC and MM configurations, it would appear the only difference between the two settings is different gain applied to each.

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

The chart above shows the Play’s frequency response as a function of input type. The dark green trace is the same analog input data from the previous graphs. The blue/red traces are for a 16-bit/44.1kHz dithered digital input signal from 5Hz to 22kHz, the purple/green traces are for a 24/96 dithered digital input signal from 5Hz to 48kHz, and finally pink/orange is 24/192 from 5Hz to 96kHz. The analog-in frequency response is identical to the 24/192 digital input (but for a restricted low-frequency extension). The behavior at low frequencies is the same across all digital input types: -0.4dB at 5Hz. The behavior at high frequencies for all digital input types is typical: the 16/44.1 plot shows brickwall filtering  just past 20kHz; the 24/96 data plot shows brickwall-type filtering right around 48kHz; and the 24/192 plot shows a gentler slope, with a -3dB point at 60kHz.

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 speaker-level outputs of the Play. For this test, the digital input was swept with a dithered 1kHz input signal from -120dBFS to 0dBFS, and the output was analyzed by the APx555. The ideal response would be a straight flat line at 0dB. Both digital input types performed similarly, approaching the ideal 0dB relative level at -110 dBFS, then yielding perfect results to 0dBFS. At -120dBFS, the 16/44.1 input data overshot the ideal output signal amplitude by 2-4dB, while the 24/96 data overshot by only 1-2dB.

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 speaker-level outputs of the Play. We can see that the Play utilizes a reconstruction filter with no pre-ringing, but significant post-ringing.

J-Test (coaxial)

The plot above shows the results of the J-Test test for the coaxial digital input measured speaker level outputs of the Play. 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 sinewave. 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 -144dBFS 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.

We see several peaks in the audioband at -105dBFS and below. This is a relatively poor J-Test result, and an indication that the Play’s DAC may have poor jitter immunity.

J-Test (optical)

The plot above shows the results of the J-Test test for the optical digital input measured speaker level outputs of the Play. We see essentially the same poor result as with the coaxial input, though this one is slightly worse.

J-Test (coaxial, 10ns jitter)

The plot above shows the results of the J-Test test for the coaxial digital input measured speaker-level outputs of the Play with sinewave jitter injected at 2kHz at the 10ns level. We see the tell-tale peaks at 10/14kHz at the -70dBFS level. Further evidence of the poor jitter immunity. The optical input produced a similar result.

J-Test (coaxial, 100ns jitter)

The plot above shows the results of the J-Test test for the coaxial digital input measured speaker-level outputs of the Play with sinewave jitter injected at 2kHz at the 100ns level. We see the tell-tale peaks at 10/14kHz at the -50dBFS level. Further evidence of the poor jitter immunity. Again, the optical input produced a similar result.

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 Play’s speaker-level outputs with white noise at -4dBFS (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 brickwall-type reconstruction filter. There are only small (-125dBFS and below) aliased image peaks in the audioband. The main 25kHz alias peak is highly suppressed at -100dBrA. The second, third, and fourth distortion harmonics (38.2, 57.3, 76.4kHz) of the 19.1kHz tone are between -60dBrA 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 input swept from 10Hz 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. Zoomed in, we can see significant deviations (2dB) at high frequencies from 4 ohms to no load, which is an indication of a very low damping factor, or high output impedance. This is typical of many class-D amplifiers. Below 5kHz, deviations are within 0.3dB. The maximum variation in RMS level when a real speaker was used was, as expected, at high frequencies, with a 0.3dB deviation between 6kHz and 20kHz. Below 2kHz, deviations with a real speaker load are small and within about 0.1dB.

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 (20Hz to 6kHz) for a sinewave stimulus at the analog input. The blue and red plots are for the left and right chanels at 1W output into 8 ohms, purple/green at 10W, and pink/orange at 61W. The power was varied using the volume control. All three THD plots are tightly clustered together, except between 3kHz and 6kHz at 61W. THD ratios ranged from around 0.04% at 20Hz, down to 0.005% from 100Hz to 3kHz, then up to between 0.006% (10W) and 0.04% (61W) at 6kHz.

THD ratio (unweighted) vs. frequency at 10W (phono input, MM and MC)

The chart above shows THD ratios as a function of frequency plots for the phono input (MM configuration blue/red traces, MC purple/green) measured across an 8-ohm load at 10W. The input sweep is EQ’d with an inverted RIAA curve. THD ratios were lower for both the right channel (5-10dB) and for the MM configuration. For MM (left channel), they ranged from roughly 0.1% to 0.01%. For MC (left channel), they ranged from 0.5% to roughly 0.01%.

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 Play as a function of output power for the analog line-level input, for an 8-ohm load (blue/red for left/right) and a 4-ohm load (purple/green for left/right), with the volume at maximum. THD ratios for the 8-ohm load ranged from 0.01% at 50mW, down to 0.002% at 0.5W to 3W, then up to 0.005% at the “knee,” at just past 68W. The 1% THD mark was reached at 75W, but is due to the ADC clipping. THD ratios for the 4-ohm load ranged from 0.01% at 50mW, down to 0.002% at 0.5W to 2W, then up to 0.02% at 20W, then 0.01% at  the “knee,” at around 110W. The 1% THD mark was reached at 142W.

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 Play as a function of output power for the analog line-level-input, for an 8-ohm load (blue/red for left/right) and a 4-ohm load (purple/green for left/right), with the volume set to maximum. THD+N ratios for the 8-ohm load ranged from 0.07% at 50mW, down to 0.005% at the “knee.” THD+N ratios for the 4-ohm load ranged from 0.1% at 50mW, down to 0.01% at  the “knee,” with a bump to 0.02% at 20W.

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 Play as a function of load (8/4/2 ohms) for a constant input voltage that yielded 5W at the output into 8 ohms (and roughly 10W into 4 ohms, and 20W 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 that THD ratios for all three loads are closely clustered together, other than between 800Hz and 1kHz, where the 2-ohm load yielded 10dB higher results. Otherwise, THD ratios ranged from 0.05% down to 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 Play 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). Generally, THD ratios are closely clustered together, with real speaker THD ratios hovering above and below the resistive dummy load data with +/- 5dB. The dummy load ranged from 0.03% at 20Hz, down to 0.005% from 100Hz to 1kHz, then up to 0.01% at 6kHz.

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 Play 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). Generally, IMD ratios were higher into the real speaker loads, with the three-way speaker yielding the worst results at between 0.02% and 0.05%, compared to the resistive load at 0.005% across most of the sweep. The 2-way speaker ranged from 0.007% to 0.04%.

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 Play 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). We find very similar IMD ratios into all three loads, a constant 0.02% from 40Hz to 500Hz, then down to 0.004% to 1kHz.

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 (2kHz), third (3kHz), fourth (4kHz), and fifth (5kHz) harmonics are evident at -90/-100/-110-/120dBrA respectively, or 0.003% to 0.0001%. Subsequent signal harmonics can also be seen around the -120dBrA level. Below 1kHz, we see small power-supply-related noise peaks at 60Hz and 120Hz, right around -120dBrA, or 0.0001%.

FFT spectrum – 1kHz (MM phono 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 phono input configured for MM. Signal harmonics are slightly higher in level compared to the line-level FFT above (-80 to -110dBrA). Power-supply-related noise peaks can be seen at 60Hz and more predominantly at the odd harmonics (180/300/420/540/660 Hz etc) from -90dBrA, or 0.003%, to -110dBrA, or 0.0003%.

FFT spectrum – 1kHz (MC phono 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 phono input configured for MC. Signal harmonics are difficult to distinguish from the myriad noise peaks reaching roughly -90dBrA, or 0.003%. The signal’s second (2kHz) harmonic can, however, clearly be seen at -70/80dBrA (left/right), or 0.03/0.01%. Power-supply-related noise peaks are again dominated at 60Hz and the odd harmonics, from -70dBrA to -90dBrA, or 0.03% to 0.003%.

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. We see odd/even signal harmonics at -110dBrA to -120dBrA, or 0.0003% to 0.0001%. Noise peaks to the left of the signal peak are non-existent above the -130dBrA noise floor.

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. We see essentially the same signal harmonic profile as with 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 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 no signal or noise related harmonic peaks.

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 two small random noise peaks at a very low -140dBrA, or 0.00001%.

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 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 the signal second (100Hz) and third (150Hz) harmonics at around -80dBrA and -90dBrA, or 0.01% and 0.003%, with other signal harmonics seen below -110dBrA. The worst-case noise peak is at 60Hz at -110dBrA, or 0.0003%.

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 phono input with the 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 (non-signal) peaks are the signal second (100Hz) and third (150Hz) harmonics at around -70/-80dBrA (left/right) and -80dBrA, with other signal harmonics seen at and below -100dBrA. The worst-case noise peak is at 60Hz at -90dBrA, or 0.003%.

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 phono input with the MC configuration. 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 the signal second (100Hz) harmonic at around -50/-60dBrA (left/right), or 0.3% and 0.1%, with other signal harmonics seen at and below -80dBrA. The worst-case noise peak is at 60Hz at -70dBrA, or 0.03%.

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 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 around -90dBrA, or 0.003%.

Intermodulation distortion FFT (line-level input, APx 32 tone)

Shown above is the FFT of the speaker-level output of the Play with the APx 32-tone signal applied to the analog input. The combined amplitude of the 32 tones is the 0dBrA reference, and corresponds to 10W into 8 ohms. The intermodulation products—i.e., the “grass” between the test tones—are distortion products from the amplifier and are at and below the low -110dBrA, or 0.0003%, 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 -120dBrA, or 0.0001%, while the third-order modulation products, at 17kHz and 20kHz, are around -90dBrA, or 0.003%.

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 coaxial optical input at 24/96. We find that the second-order modulation product (i.e., the difference signal of 1kHz) is at -120dBrA, or 0.0001%, while the third-order modulation products, at 17kHz and 20kHz, are around -90dBrA, or 0.003%.

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 phono input configured for MM. 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%, while the third-order modulation products, at 17kHz and 20kHz, are at 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 phono input configured for MC. 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 at -85dBrA, or 0.006%.

Squarewave response (10kHz)

Above is the 10kHz squarewave response using the analog 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 Play’s slew-rate performance. Rather, it should be seen as a qualitative representation of its limited 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. Due to Play’s limited bandwidth, we can see overshoot in the corners. In addition, we can see the 450kHz switching oscillator frequency used in the digital amplifier section visibly modulating the waveform.

Squarewave response (1kHz)

Above is the 1kHz squarewave response using the analog input, at roughly 10W into 8 ohms, with a 250kHz restricted bandwidth to remove the modulation from the 450kHz oscillator. Here we see a relatively clean square wave reproduction, with just some over-shoot in the corners.

FFT spectrum of 400kHz switching frequency relative to a 1kHz tone

The Play’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 Play oscillator switches at a rate of about 450kHz, 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 450kHz peak is quite evident, and at -30dBrA. There is also a peak at 900kHz (the second harmonic of the 450kHz peak), at -60dBrA. Those peaks are direct results of the switching oscillators in the Play’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 plot above is the damping factor as a function of frequency. Both channels show a relatively constant damping factor from 20Hz to 2kHz, then a steep dip, characteristic of many class-D amps.  At low frequencies, the damping factor is high at around 130/120 (left/right), but at 20kHz the damping factor dips to a very low 10.

Diego Estan
Electronics Measurement Specialist

Details

Parent Category: Products

Category: Amplifier Measurements

Created: 01 September 2025

Link: reviewed by Jason Thorpe on SoundStage! Ultra on September 1, 2025

General Information

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

The Marantz Model 10 was conditioned for 1 hour at 1/8th full rated power (~30W 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 Model 10 offers five analog line-level inputs (three RCA, two XLR), one set of phono inputs (RCA, configurable for MM or MC), line-level pre-outs (RCA and XLR), line-level power-amp inputs (RCA and XLR), and two pair of speaker level outputs. In addition, a ¼″ TRS headphone jack can be found on the front panel. For the purposes of these measurements, the following inputs were evaluated: analog line-level balanced (XLR) input, phono (MM and MC), and the headphone output. There were no appreciable differences between the RCA and XLR inputs in terms of THD and noise, but 1kHz FFTs for both are shown in this report. The balanced inputs offer 6dB less gain than the unbalanced inputs (i.e., the designers expect balanced incoming signals to have twice the voltage as unbalanced signals).

Most measurements were made with a 4Vrms line-level analog input, 5mVrms MM input and 0.5mVrms MC input. For the MC configuration, the Model 10 offers three settings with different input impedances (Low at 33 ohms, Mid at 100 ohms, and High at 390 ohms). For the purposes of these measurements, the Mid setting was used. 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 250W. For comparison, on the analog input, a SNR measurement was also made with the volume at maximum.

Based on the accuracy and randomness at various volume levels of the left/right channel matching (see table below), the Model 10 volume control is likely digitally controlled but operating in the analog domain. The volume control offers a total range from -62dB to +36.4dB (XLR line-level input to speaker level outputs). The range is -99.5dB to 0dB, in 0.5dB increments.

Our typical input bandwidth filter setting of 10Hz-22.4kHz was used for all measurements except FFTs, where a bandwidth of 10Hz-90kHz was used. Frequency response measurements utilize a DC to 1 MHz input bandwidth. Because the Model 10 is a digital amplifier technology that exhibits 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

Published specifications vs. our primary measurements

The table below summarizes the measurements published by Marantz for the Model 10 compared directly against our own. The published specifications are sourced from Marantz’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 set at its maximum (DC to 1MHz), assume, unless otherwise stated, a measurement input bandwidth of 10Hz to 22.4kHz, and the worst-case measured result between the left and right channels.

Our primary measurements revealed the following using the analog input (unless specified, assume a 1kHz sinewave at 4Vrms, 10W output, 8-ohm loading, 10Hz to 22.4kHz bandwidth):

For the continuous dynamic power test, the Model 10 was able to sustain 750W (3% THD) into 4 ohms using an 80 Hz tone for 500ms, alternating with a signal at -10 dB of the peak (75W) 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 Model 10 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):

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):

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

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

In our measured frequency-response (relative to 1kHz) chart above, the Model 10 is essentially perfectly flat within the audioband (20Hz to 20kHz). At the extremes the Model 10 is 0dB at 5Hz, and -3dB at just past 60kHz. 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 at maximum and minimum)

Above are two frequency-response plots (relative to 1kHz) for the analog input, measured at 10W (8-ohm) at the speaker outputs, with the treble/balance controls set at both minimum and maximum. They show that the Model 10 will provide a maximum gain/cut of approximately 11dB at 20Hz, and a maximum gain/cut of approximately 10dB at 20kHz.

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

Above is the phase response plot from 20Hz to 20kHz for the analog input. The Model 10 does not invert polarity and exhibits just past -20 degrees of phase shift at 20kHz.

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

The chart above shows the frequency response for the phono input (MM configuration) measured across the speaker outputs at 10W into 8 ohms. 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/+0.25dB (150Hz and 10kHz-20kHz) from 20Hz to 20kHz for the left channel. The right channel performed better and was essentially perfectly flat within the audioband. Below 20Hz, there’s a significant rise in response, peaking at +2.5dB at 6-7Hz. The high frequency response (above 20kHz) is the same as the line-level response above.

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 Model 10 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 -120 degrees at 20kHz.

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

The chart above shows the frequency response for the phono input (MC configuration) measured across the speaker outputs at 10W into 8 ohms. We see essentially the same response as with the MM configuration above.

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. We see essentially the same response as with the MM configuration above.

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 input swept from 10Hz 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. Zoomed in, we can see a maximum deviation within the audio band of just above 0.02dB from 4 ohms to no load, which is an indication of a very high damping factor, or low output impedance. The maximum variation in RMS level when a real speaker was smaller, deviating by about 0.01dB within the flat portion of the curve (20Hz to 10kHz).

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 (20Hz to 6kHz) for a sinewave stimulus at the analog input. The blue and red plots are for left and right channel at 1W output into 8 ohms, purple/green at 10W, and pink/orange at 250W (rated power). The 10W data exhibited the lowest THD values, 0.0001% from 20Hz to 1kHz, then up to 0.00025% at 6kHz. The 1W data hovered around the 0.0002% across the sweep, and the 250W THD data ranged from 0.0001-0.0002% at 20Hz to 200Hz, then a steady rise to 0.001% at 6kHz.

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

The chart above shows THD ratio as a function of frequency plots for the phono input measured across an 8-ohm load at 10W for the MM (blue/red) and MC (purple/green) configurations. The input sweep is EQ’d with an inverted RIAA curve. The MM THD values vary from around 0.005% at 20Hz then a steady decline down to 0.0003% at 6kHz. The MC THD values vary from around 0.05% at 20Hz then a steady decline down to 0.0005% at 6kHz. The decline in THD values as a function of frequency is a function of the noise floor reduction at higher frequencies due to the implementation of RIAA equalization. The analyzer cannot assign a THD value for a harmonic peak it cannot see below the noise floor.

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 Model 10 as a function of output power for the analog line level-input, for an 8-ohm load (blue/red for left/right) and a 4-ohm load (purple/green for left/right), with the volume set to maximum. The 8 and 4-ohm data are closely matched (with 2-3dB). The 8-ohm THD data range from 0.003% at 50mW, down to 0.0002% just before the “knee,” at roughly 220W. The 4-ohm THD data range from 0.005% at 50mW, down to 0.0003% just before the “knee,” at roughly 500W. The 1% THD marks were seen at 340W and 650W.

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 Model 10 as a function of output power for the analog line level-input, for an 8-ohm load (blue/red for left/right) and a 4-ohm load (purple/green for left/right), with the volume set to maximum. The 4-ohm data yielded a consistent 3-4dB higher THD+N result across the sweep compared to the 8-ohm data. The 8-ohm data ranged from 0.03% at 50mW down to 0.0006% at the “knee.”  The 4-ohm data ranged from 0.05% at 50mW down to 0.0006% at the “knee.”

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 Model 10 as a function of load (8/4/2 ohms) for a constant input voltage that yielded 100W at the output into 8 ohms (and roughly 200W into 4 ohms, and 400W 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 increasing levels of THD from 8 to 4 (2-3dB) to 2 ohms (6-7dB). Overall, even with a 2-ohm load at roughly 400W, THD values were fairly low and flat within the audioband, between 0.0004% and 0.001%.

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 Model 10 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). The measured THD ratios for the real speakers were higher than for the 8-ohm resistive load between 20Hz and 400Hz. The highest result, as is usually the case, was at 20Hz into the two-way speaker at 0.01%, compared to 0.0002% into the dummy load. At 100Hz, both speakers yielded THD ratios of 0.0006%, compared to 0.0002% into the dummy load. In the important midrange frequencies of 400Hz to 6kHz, all THD ratios were essentially the same, between 0.0002% and 0.0001%.

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 Model 10 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 IMD results are similar, hovering from 0.0005% to 0.001% across the measured frequency range.

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 Model 10 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 IMD results are effectively the same, hovering just below 0.002% across the sweep.

FFT spectrum – 1kHz (XLR 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 XLR input. We see that the signal’s second (2kHz) and third (3kHz) harmonics dominate at -140/-130dBrA (left/right), or 0.00003/0.00001%, and -120dBrA, or 0.0001%. Subsequent signal harmonics can be seen at -135dBrA and below. Below 1kHz, we see traditional noise peaks from the implementation of a linear power supply at the odd-harmonic positions (60/180/300/420/540Hz etc). Given the enormous size of the power supply, however, the peaks are low in level, at -130/-120dBrA (left/right) and below. We also see a rise in the noise floor above 30kHz, indicative of digital amplifier technology.

FFT spectrum – 1kHz (RCA 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 RCA input. The FFT is almost identical to the balanced FFT above, except for a slightly higher peak at the second (2kHz) harmonic position.

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 phono input (MM configuration). We see the second (2kHz) signal harmonic dominating at around -110dBrA, or 0.0003%. Other signal harmonics are difficult to identify amongst the power-supply-related noise peaks. The most significant power-supply-related noise peak can be seen at 180Hz at -90dBrA, or 0.003%. Higher-order power-supply-related peaks can also be seen at lower amplitudes.

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 phono input (MC configuration). We see the second (2kHz) signal harmonic dominating at around -100dBrA, or 0.001%. Other signal harmonics are difficult to identify amongst the power-supply-related noise peaks. The most significant power-supply-related noise peak can be seen at 180Hz at -70dBrA, or 0.03%. Higher order power-supply-related peaks can also be seen at lower amplitudes.

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 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) peaks are the signal third (150Hz) signal harmonic and the power-supply-related third (180Hz) harmonic, both around -120dBrA or 0.0001%. Subsequent power-supply-related noise peaks can be seen just below the -120dBrA level.

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 phono input (MM configuration). 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) peaks are the signal second (100Hz) harmonic and the power-supply-related third (180Hz) harmonic, at -95dBrA, or 0.002%, and -90dBrA, or 0.003%.

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 phono input (MC configuration). 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) peaks are the power-supply-related primary (60Hz) and third (180Hz) harmonics, at -75dBrA, or 0.02%, and -70dBrA, or 0.03%. Signal harmonics are difficult to identify above the higher noise-floor.

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 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 -120dBrA, or 0.0001%, while the third-order modulation products, at 17kHz and 20kHz, are just below -110dBrA, or 0.0003%.

Intermodulation distortion FFT (line-level input, APx 32 tone)

Shown above is the FFT of the speaker-level output of the Model 10 with the APx 32-tone signal applied to the input. The combined amplitude of the 32 tones is the 0dBrA reference, and corresponds to 10W into 8 ohms. The intermodulation products—i.e., the “grass” between the test tones—are distortion products from the amplifier and below the very low -140dBrA, or 0.00001%, 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 phono input (MM configuration). We find that the second-order modulation product (i.e., the difference signal of 1kHz) is at -90dBRa, or 0.003%, while the third-order modulation products, at 17kHz and 20kHz, are just below -110dBrA, or 0.0003%.

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 phono input (MC configuration). We find that the second-order modulation product (i.e., the difference signal of 1kHz) is at -90dBRa, or 0.003%, while the third-order modulation products, at 17kHz and 20kHz, are just below -110dBrA, or 0.0003% (right channel only).

Squarewave response (10kHz)

Above is the 10kHz squarewave response using the analog 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 Model 10’s slew-rate performance. Rather, it should be seen as a qualitative representation of its reasonably 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. Due to Model 10’s bandwidth, we can see visible over-shoot in the corners of the waveform. In addition, we can see the 700kHz switching oscillator frequency used in the digital amplifier section visibly modulating the waveform.

Squarewave response (10kHz, 250kHz bandwidth)

Above is the same 10kHz squarewave response using the analog input as seen in the graph above, but this time applying a 250kHz bandwidth filter in the analyzer to remove the effect from the switching oscillator. We find the same visible over-shoot in the corners of the waveform.

FFT spectrum of 700kHz switching frequency relative to a 1kHz tone

The Model 10’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 oscillator switches at a rate of about 700kHz, 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 700kHz peak is quite evident at -50dBrA. We also see a clear rise in the noise floor above 30kHz all the way to the 700kHz peak. This very-high-frequency noise is in the signal, but is far above the audio band—and is 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 plot above is the damping factor as a function of frequency. Both channels show a relatively constant damping factor from 20Hz to 20kHz. The damping factor for the left channel ranges from just over 1000 down to 700 at 20kHz, while the right channel ranges from 900 down to 600 at 20kHz. These are very high damping factor results, and they explain the Model 10’s exemplary flat frequency-response results into different loads.

Diego Estan
Electronics Measurement Specialist