Link: reviewed by Dennis Burger on *SoundStage! Access* on March 1, 2024

**General Information**

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

The Dayton Audio HTA200 was conditioned for one hour at 1/8th full rated power (~4W 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 HTA200 offers one pair of line-level analog inputs (RCA), one pair of moving-magnet (MM) phono inputs (RCA), an RCA sub output, one digital coaxial (RCA) input, one optical (TosLink) input, one USB digital input, a pair of speaker level outputs and one headphone output over 1/4″ TRS connector. A Bluetooth input is also offered. For the purposes of these measurements, the following inputs were evaluated: digital coaxial, analog line-level, as well as phono.

Most measurements were made with a 2Vrms line-level analog input, 5mVrms MM input, and 0dBFS digital input. The signal-to-noise (SNR) measurements were made with the default input signal values but with the volume set to achieve the rated output power of 70W (4 ohms). For comparison, on the line-level input, a SNR measurement was also made with the volume at maximum.

Based on the inaccuracy and non-repeatability of the left/right volume channel matching (see table below), the HTA200 volume control is a potentiometer operating in the analog domain. The HTA200 overall volume range is from -59dB to +28.6dB (line-level input, speaker output).

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

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

Volume position | Channel deviation |

min | 11.5dB |

9 o'clock | 0.068dB |

12 o'clock | 0.3dB |

3 o'clock | 0.65dB |

max | 0.6dB |

**Published specifications vs. our primary measurements**

The table below summarizes the measurements published by Dayton Audio for the HTA200 compared directly against our own. The published specifications are sourced from Dayton’s manual provided with the review sample (note: the PDF availiable on Dayton's website shows much higher power ratings that are less realistic than those shown here). 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.

Parameter | Manufacturer | SoundStage! Lab |

Maximum power output (4 ohms, peak/IHF) | 140W | 148W |

RMS power output (4 ohms, 1.5% THD) | 70W | 82W |

Gain (line-level) | 29dB | 28.6dB/27.9dB (L/R) |

THD+N (at 70W into 4 ohms) | 1.5% | 1.4% |

Frequency response (analog line-level in) | 15Hz-20kHz (±1dB) | 15Hz-20kHz (±1dB) |

Input sensitivity (for 70W into 4ohms, max volume) | 630mVrms | 630/675mVrms (L/R) |

Channel separation (1kHz, 70W 4 ohms) | 53dB | 57dB |

SNR (1kHz, 70W 4 ohms, A-weighted) | 80dB | 90dB |

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

Parameter | Left channel | Right channel |

Maximum output power into 8 ohms (1% THD+N, unweighted) | 16.5W | 16.5W |

Maximum output power into 4 ohms (1% THD+N, unweighted) | 32W | 32W |

Maximum burst output power (IHF, 8 ohms) | 93W | 93W |

Maximum burst output power (IHF, 4 ohms) | 148W | 148W |

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

Crosstalk, one channel driven (10kHz) | -43.9dB | -46.5dB |

Damping factor | 108 | 85 |

Clipping no-load output voltage | 11.8Vrms | 11.8Vrms |

DC offset | <12mV | <6mV |

Gain (sub-out) | 3.2dB | N/A |

Gain (maximum volume) | 28.6dB | 27.9dB |

IMD ratio (CCIF, 18kHz + 19kHz stimulus tones, 1:1) | <-41dB | <-41dB |

IMD ratio (SMPTE, 60Hz + 7kHz stimulus tones, 4:1 ) | <-31dB | <-31dB |

Input impedance (line input, RCA) | 15.3k ohms | 15.3k ohms |

Input sensitivity (70W 4 ohms, maximum volume) | 630mVrms | 675mVrms |

Noise level (with signal, A-weighted) | N/A | N/A |

Noise level (with signal, 20Hz to 20kHz) | N/A | N/A |

Noise level (no signal, A-weighted, volume min) | <175uVrms | <190uVrms |

Noise level (no signal, 20Hz to 20kHz, volume min) | <300uVrms | <420uVrms |

Output impedance (pre-out) | 2806 ohms | N/A |

Signal-to-noise ratio (70W into 4 ohms, A-weighted, 2Vrms in) | 89.8dB | 89.9dB |

Signal-to-noise ratio (70W into 4 ohms, 20Hz to 20kHz, 2Vrms in) | 88.0dB | 87.2dB |

Signal-to-noise ratio (70W into 4 ohms, A-weighted, max volume) | 81.1dB | 81.0dB |

Dynamic range (70W into 4 ohms, A-weighted, digital 24/96) | 92.4dB | 92.5dB |

Dynamic range (70W into 4 ohms, A-weighted, digital 16/44.1) | 91.3dB | 91.3dB |

THD ratio (unweighted) | <0.75% | <0.78% |

THD ratio (unweighted, digital 24/96) | <0.82% | <0.85% |

THD ratio (unweighted, digital 16/44.1) | <0.82% | <0.87% |

THD+N ratio (A-weighted) | <0.86% | <0.89% |

THD+N ratio (A-weighted, digital 24/96) | <0.90% | <0.95% |

THD+N ratio (A-weighted, digital 16/44.1) | <0.92% | <0.98% |

THD+N ratio (unweighted) | <0.75% | <0.78% |

Minimum observed line AC voltage | 126VAC | 126VAC |

For the continuous dynamic power test, the HTA200 was able to sustain 133W into 4 ohms (~7% THD) using an 80Hz tone for 500ms, alternating with a signal at -10dB of the peak (13.3W) for five seconds, for five continuous minutes without inducing a fault or the initiation of a protective circuit. This test is meant to simulate sporadic dynamic bass peaks in music and movies. During the test, the top of the HTA200 (except for the tubes) was only slightly warm to the touch.

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

Parameter | Left channel | Right channel |

Crosstalk, one channel driven (10kHz) | -47.2dB | -50.6dB |

DC offset | <10mV | <8mV |

Gain (default phono preamplifier) | 36.7dB | 36.7dB |

IMD ratio (CCIF, 18kHz + 19kHz stimulus tones, 1:1) | <-40dB | <-40dB |

IMD ratio (CCIF, 3kHz + 4kHz stimulus tones, 1:1) | <-40dB | <-40dB |

Input impedance | 52.8k ohms | 53.3k ohms |

Input sensitivity (to 10W with max volume) | 5mVrms | 5mVrms |

Noise level (with signal, A-weighted) | <1.6mVrms | <1.5mVrms |

Noise level (with signal, 20Hz to 20kHz) | <8.5mVrms | <3.4mVrms |

Noise level (no signal, A-weighted, volume min) | <0.170mVrms | <0.185mVrms |

Noise level (no signal, 20Hz to 20kHz, volume min) | <0.290mVrms | <0.420mVrms |

Overload margin (relative 5mVrms input, 1kHz) | 15.8dB | 15.8dB |

Signal-to-noise ratio (10W, A-weighted, 5mVrms in) | 71.4dB | 72.8dB |

Signal-to-noise ratio (10W, 20Hz to 20kHz, 5mVrms in) | 56.6dB | 69.7dB |

THD (unweighted) | <0.79% | <0.75% |

THD+N (A-weighted) | <0.90% | <0.86% |

THD+N (unweighted) | <0.79% | <0.75% |

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

Parameter | Left and right channels |

Maximum gain | 2.8dB |

Maximum output power into 600 ohms (1% THD) | 15mW |

Maximum output power into 300 ohms (1% THD) | 29mW |

Maximum output power into 32 ohms (1% THD) | 25mW |

Output impedance | 10.5 ohms |

Maximum output voltage (1% THD into 100k ohm load) | 3.06Vrms |

Noise level (with signal, A-weighted) | <90uVrms |

Noise level (with signal, 20Hz to 20kHz) | <125uVrms |

Noise level (no signal, A-weighted, volume min) | <8.2uVrms |

Noise level (no signal, 20Hz to 20kHz, volume min) | <11uVrms |

Signal-to-noise ratio (A-weighted, 1% THD, 3Vrms out) | 92dB |

Signal-to-noise ratio (20Hz - 20kHz, 1% THD, 3Vrms out) | 89dB |

THD ratio (unweighted) | <0.035% |

THD+N ratio (A-weighted) | <0.035% |

THD+N ratio (unweighted) | <0.035% |

**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 HTA200 is not flat within the audioband (20Hz to 20kHz). There’s a +1dB rise in the frequency response at 40Hz and at nearly 20kHz. There’s also a -0.3dB dip at 5-7kHz. The HTA200 appears to be AC coupled (or at least purposefully high-pass filtered) with a -3dB point at 10Hz. There is extreme brickwall-type filtering at 20kHz, with a -3dB point at around 21.8kHz. There is a high probability that the analog input is digitized, because this type of brickwall filtering is easier to implement in the digital domain. Further evidence for this can be seen in the FFTs in this report. In the graph above and most of the graphs below, only a single trace may be visible. This is because the left channel (blue or purple trace) is performing identically to the right channel (red or green trace), and so they perfectly overlap, indicating that the two channels are ideally matched.

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

Above is a frequency response plot measured at the speaker-level outputs into 8 ohms, with the bass and treble controls set to maximum (blue/red plots) and minimum (purple/green plots). We see that for the bass and treble controls, roughly +7.5/-6.5dB of gain/cut is available centered at 100Hz/8kHz.

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

Above are the phase-response plots from 20Hz to 20kHz (wrapped, or every time the phase delay exceeds 360 degrees, the plot loops back up to +180 degrees) for the line-level input, measured across the speaker outputs at 10W into 8 ohms. The HTA200 appears to invert polarity and yields an astonishing -60000 degrees of phase shift at 20kHz.

**Frequency response (line-level sub out)**

Above is the frequency-response plot (relative to 80Hz) measured at the line-level sub out of the HTA200. The same rise at 40Hz that was observed at the speaker-level outputs can be seen here. The -3dB point is just past 2kHz.

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

The chart above shows the HTA200’s frequency response (relative to 1kHz) as a function of input type measured across the speaker outputs at 10W into 8 ohms. The pink trace is the same analog input data from the previous graph. The blue trace is for a 16-bit/44.1kHz dithered digital input signal from 5Hz to 22kHz using the coaxial input, and the purple trace is for a 24/96 dithered digital input signal from 5Hz to 48kHz, and the 24/192 dithered digital input signal is not shown because it yielded the same result as the 24/96 data. Because the HTA200 appears to digitize incoming analog signals, as well as resample all digital signals to 44.1kHz, the same brickwall-type behavior is seen right at 20kHz regardless of the input type. At low frequencies, there is slightly more extension for the analog input, with a -3dB point at 10Hz versus about 12Hz for the digital input. The digital input shows less significant deviations within the audioband, with a rise of only 0.5dB at 50Hz versus the 1dB rise at 40Hz for the analog input. The same is true at 20kHz, where the digital input is at +0.25dB compared to the +0.8dB for the analog signal.

**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 maximum deviation of about -5dB/+0.8dB (20Hz and 20kHz) from 20Hz to 20kHz. The dip at 5-7kHz seen with the line-level input is also seen here; however, with a channel-to-channel deviation of about 0.3dB (from 5kHz to 20kHz).

**Phase response (MM input)**

Above is the phase-response plot from 20Hz to 20kHz (excess, or above and beyond the true input to output phase delay as seen in the plot for the line-level input above) for the phono input (MM configuration) measured across the speaker outputs at 10W into 8 ohms. For the phono input, since the RIAA equalization curve must be implemented, which ranges from +19.9dB (20Hz) to -32.6dB (90kHz), phase shift at the output is inevitable. Here we find a worst case of about +150 degrees at 20Hz.

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

The chart above shows the results of a linearity test for the coaxial digital input for both 16/44.1 (blue/red) and 24/96 (purple/green) input data, measured at the speaker outputs of the HTA200 at 1W into 8 ohms. 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. The 16/44.1 data were essentially perfect as of -90dBFS down to 0dBFS, while the 24/96 data were near perfect down to -100dBFS. Both overshot the mark by over 10dB at -120dBFS. This is a poor linearity-test result, although it should be pointed that the linearity test is measured at the line-level pre-out when available. In this case, there are none, and the speaker outputs will invariably be noisier.

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

The graph above shows the impulse response for the HTA200, fed to the coaxial digital input, measured at the speaker level output at 1W into 8ohms, for a looped 24/44.1 test file that moves from digital silence to full 0dBFS (all “1”s), for one sample period then back to digital silence. We find a reconstruction filter that adheres to a typical symmetrical sinc function, although the HTA200 does invert polarity.

**J-Test (coaxial)**

The chart above shows the results of the J-Test test for the coaxial digital input measured at the speaker level output of the HTA200 at 1W into 8 ohms. 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 (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.

It is difficult to assess the results, with the significant rise in the noise floor (-80dBrA) centered on the main peak. We see a peak at -75dBrA at 8kHz, and another at -85dBrA at 16kHz. This is a poor J-Test result, indicating that the HTA200 DAC may be susceptible to jitter. When we attempted to inject artificial jitter at a level of only 10ns, we could not capture a reliable result.

**J-Test (optical)**

The chart above shows the results of the J-Test test for the optical digital input measured at the speaker-level output of the HTA200 at 1W into 8 ohms. The optical input yielded essentially the same result as the coaxial 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 HTA200’s speaker level output at 1W into 8 ohms, with white noise at -4dBFS (blue/red) and a 19.1 kHz sinewave at -1dBFS fed to the coaxial digital input, sampled at 16/44.1. The steep roll-off around 20kHz in the white-noise spectrum shows the brickwall-type behavior of the HTA200’s reconstruction filter. There are low-level aliased image peaks within the audioband at the -100dBrA level. The primary aliasing signal at 25kHz cannot be seen and is completely suppressed, while the second and third distortion harmonics (38.2, 57.3kHz) of the 19.1kHz tone are at -55dBrA.

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

The chart above shows RMS level (relative to 0dBrA, which is 1W into 8ohms or 2.83Vrms) as a function of frequency, for the analog line-level input swept from 5Hz to 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 find that between 100Hz and 8kHz, the deviations between no load and 4 ohms are around 0.15dB. This is a fair result for a class-AB amp, and an indication of a relatively low output impedance, or high damping factor. Due to the nonlinear nature of the HTA200’s frequency response, it is difficult to assess the fluctuations in response versus frequency for the real speaker load.

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

The chart above shows THD ratios at the output into 8 ohms as a function of frequency for a sinewave stimulus at the analog line-level input. The blue and red plots are for left and right channels at 1W output into 8 ohms, purple/green at 10W, and pink/orange just under 35W. The power was varied using the HTA200 volume control. At 1W, THD ratios are fairly constant at 0.3% from 20Hz to 20kHz. At 10W, THD ratios are fairly constant across the audioband from 1% to 0.8%, while at 35W, THD ratios are as high as 2% at 20Hz, then a constant 1.5% from 100Hz to 20kHz. The HTA200 is definitely a high-distortion amplifier, considering the class-AB transistor-based output.

**THD ratio (unweighted) vs. frequency at 10W (MM 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. The input sweep is EQ’d with an inverted RIAA curve. The THD values vary from around 0.5% to 0.8% across the audioband.

**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 HTA200 as a function of output power for the analog line-level input, for an 8-ohm load (blue/red for left/right channels) and a 4-ohm load (purple/green for left/right channels). Both data sets track closely except for maximum power, with the 4-ohm data slightly outperforming (2-3dB) the 8-ohm data at medium power. THD ratios range from as low as 0.1% at 50mW, then a steady linear climb to the “knees” at 80W (2% into 8 ohms) and just past 100W (2% into 4 ohms). The 1% THD marks were reached at just 16.5W (8 ohms) and 32W (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 HTA200 as a function of output power for the line-level input, for an 8-ohm load (blue/red for left/right channels) and a 4-ohm load (purple/green for left/right channels). Both data sets track closely except for maximum power, with the 4-ohm data slightly outperforming (2-3dB) the 8-ohm data at lower power. Overall, THD+N values for both loads ranged from 0.2% at 50mW, then a steady linear climb to the “knees” at 80W (2% into 8 ohms) and just past 100W (2% into 4 ohms). Because THD ratios are so high with the HTA200, it’s the THD component of THD+N that dominates in these graphs.

**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 HTA200 as a function of frequency into three different loads (8/4/2 ohms) for a constant input voltage that yielded 10W at the output into 8 ohms (and roughly 20W into 4 ohms, and 40W into 2 ohms) for the analog line-level input. The 8-ohm load is the blue trace, the 4-ohm load the purple trace, and the 2-ohm load the pink trace. We find essentially identical THD ratios into all three loads, from 1% to 0.8%. Ordinarily, having all three data sets plot identically would be commendable; however, in this case, THD ratios are very high for a solid-state amplifier output.

**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 HTA200 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). We find essentially identical THD ratios into all three loads, just above and below 0.3% to 0.8%. As above, ordinarily, having all three data sets plot identically would be commendable; however, in this case, THD ratios are very high for a solid-state amplifier output.

**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 HTA200 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 essentially identical IMD ratios into all three loads, around 0.3%. Once again, having all three data sets plot identically would be commendable; however, in this case, the IMD ratios are very high for a solid-state amplifier output.

**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 HTA200 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 essentially identical IMD ratios into all three loads, 1% from 40Hz to almost 500Hz, and then a dip to 0.02% from 500Hz to 1kHz. As mentioned above, having all three data sets plot identically would be commendable; however, in this case, the IMD ratios are very high for a solid-state amplifier output.

**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) harmonic dominates at a very high -40dBrA, or 1%, while subsequent signal harmonics are at and below -70dBrA, or 0.03%. On the right side of the signal peak, we see the primary (60Hz), second (120Hz), and fourth (240Hz) noise-related harmonics dominate at -85dBrA to -95dBrA, or 0.006% to 0.002%. While difficult to see in this graph, we did find two peaks at 43.1kHz and 45.1kHz, which are telltale IMD products that are a result of the 1kHz analog signal being digitized and sampled at 44.1kHz.

**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) harmonic dominates at a very high -40dBrA, or 1%, while subsequent signal harmonics are at and below -55dBrA, or 0.2%. On the right side of the signal peak, we see the primary (60Hz), second (120Hz), and fourth (240Hz) noise-related harmonics dominate at -85dBrA to -95dBrA, or 0.006% to 0.002%.

**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 that the signal’s second (2kHz) harmonic dominates at a very high -45dBrA, or 0.6%, while subsequent signal harmonics are at and below -90dBrA, or 0.003%. On the right side of the signal peak, we see the primary (60Hz), second (120Hz), and fourth (240Hz) noise-related harmonics dominate at -85dBrA to -95dBrA, or 0.006% to 0.002%.

**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 just under the correct amplitude, and noise-related peaks at -90dBrA, or 0.003%, and below.

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

Shown above is the FFT for a 1kHz -90dBFS dithered 24/96 input sinewave stimulus at the coaxial digital input, measured at the output across an 8-ohm load. We see the 1kHz primary signal peak, at just under the correct amplitude, and noise-related peaks at -90dBrA, or 0.003%, and below.

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

Shown above is the FFT for a 1kHz input sinewave stimulus, measured at the output across an 8-ohm load at 10W for the MM phono input. We see that the signal’s second (2kHz) harmonic dominates at a very high -40dBrA, or 1%, while subsequent signal harmonics are at and below -70dBrA, or 0.03%. On the right side of the signal peak, we see the primary (60Hz) noise-related peak dominate at -65/-75dBrA (left/right), or 0.06/0.02%.

**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 a high -40dBrA, or 1%. Several other signal-related harmonic peaks can be seen throughout at -70dBrA, or 0.03%, 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) peak is from the second (100Hz) signal harmonic at a high -45dBrA, or 0.6%. The worst-case noise-related peak is from the fundamental (60Hz) for the left channel at -60dBrA, or 0.1%.

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

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed 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 -45dBRa, or 0.6%, while the third-order modulation products, at 17kHz and 20kHz, are at -80dBrA, or 0.01%.

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

Shown above is the FFT of the speaker-level output of the HTA200 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 -70dBrA, or 0.03%, 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 (-1dBFS). We find that the second-order modulation product (i.e., the difference signal of 1kHz) is at -50dBrA, or 0.3%, while the third-order modulation products, at 17kHz and 20kHz, are around -75dBrA, or 0.02%.

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

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed 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 -50dBrA, or 0.3%, 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 MM phono input. We find that the second-order modulation product (i.e., the difference signal of 1kHz) is at -50dBrA, or 0.3%, while the third-order modulation products, at 17kHz and 20kHz, are around -60dBrA, or 0.1%.

**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 HTA200’s slew-rate performance. Rather, it should be seen as a qualitative representation of the HTA200’s extremely restricted bandwidth. An ideal squarewave can be represented as the sum of a sinewave and an infinite series of its odd-order harmonics (e.g., 10kHz + 30kHz + 50kHz + 70kHz . . .). A limited bandwidth will show only the sum of the lower-order harmonics, which may result in noticeable undershoot and/or overshoot, and softening of the edges. In this case, because of the brickwall-type cutoff at 20kHz, we find only the 10kHz fundamental sinewave, with all the upper harmonics filtered out.

**Squarewave response (1kHz)**

Above is the 1kHz squarewave response using the analog line-level input, at roughly 10W into 8 ohms, We can see significant overshoot/undershoot in the corners of the squarewave, a consequence of the HTA200’s limited bandwidth.

**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 right around 100, from 20Hz to 20kHz.

*Diego Estan*

Electronics Measurement Specialist