Hegel Music Systems H150 Streaming Integrated Amplifier Measurements

Link: reviewed by Roger Kanno on SoundStage! Hi-Fi on February 15, 2026

General Information

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

The Hegel Music Systems H150 was conditioned for 1 hour at 1/8th full rated power (~9W into 8 ohms) before any measurements were taken. All measurements were taken with both channels driven, using a 120V/20A dedicated circuit, unless otherwise stated.

The H150 offers two sets of line-level analog inputs (RCA and XLR), one RCA phono MM input, three digital S/PDIF inputs (two optical over Toslink and one coaxial over RCA), one USB digital input, left/right pre-outs, one set of speaker-level outputs, and one headphone output over 1/4″ TRS connector. For the purposes of these measurements, the following inputs were evaluated: digital coaxial, analog (XLR) line-level and phono (RCA), as well as the headphone output. There were no appreciable differences between the RCA and XLR line-level inputs in terms of gain, THD, and noise. Nonetheless, 1kHz FFTs are provided for each in this report.

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 75W 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 H150 volume control is digitally controlled but operating in the analog domain. The H150 overall volume range is from -70dB to +31.6dB (line-level input, speaker output). It offers 2-3dB increments from position 0 to 9, then 1dB increments from positions 10 to 100. Of note, some volume steps offer no change in output level.

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.

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 Hegel for the H150 compared directly against our own. The published specifications are sourced from Hegel’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 H150 was able to sustain 134W into 4 ohms (~3% THD) using an 80Hz tone for 500ms, alternating with a signal at -10dB of the peak (13.4W) for 5 seconds, for 5 minutes without inducing a fault protection circuit. This test is meant to simulate sporadic dynamic bass peaks in music and movies. During the test, the top of the H150 was hot 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 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 H150 is near flat within the audioband (20Hz/20kHz, -0.2/-0.05dB). The -3dB point is beyond 200kHz. The H150 appears to be AC coupled, demonstrated by it being -2dB 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 H150 did not invert polarity and yielded only about +10 degrees of phase shift at 20Hz, and -10 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 small channel-to-channel deviations below 1kHz (within 0.1dB), but as much as 0.7dB deviations between 5kHz and 20kHz. At 20Hz, the response is down about 2.5dB. Between 50Hz to 20kHz, RIAA deviations are within +/- 0.5dB for the left channel, and +/- 0.2dB for the right channel.

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

Above is the phase-response plot from 20Hz to 20kHz for the MM phono input, measured across the speaker outputs at 10W into 8 ohms. The H150 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 +40 degrees at 20Hz and -90 degrees at 20kHz.

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

The chart above shows the H150’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 (but limited to 80kHz). 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. All signal sweeps yielded the same -2dB at 5Hz response. The -3dB points are: 21kHz for the 16/44.1 data, 46kHz for the 24/96, 50.3kHz for the 24/192 data. Also of note, all digital inputs showed brick-wall-type high-frequency filtering, with a 0.5-1dB rise in response past 20kHz.

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 H150, where 0dBFS was set to yield 2Vrms. 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 werewithin 0.5dB at -120dBFS, while the 16/44.1 data were +2dB 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 H150. We see 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 H150 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 a mediocre J-Test result, with several peaks in the audioband, ranging from -115dBFS down to -150dBFS. This is an indication that the H150 DAC may have average 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 H150. The optical input yielded essentially the same result compared to the coaxial input.

J-Test (coaxial, 10ns 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 H150, with an additional 10ns of 2kHz sinewave jitter injected by the APx555. At this level of jitter, we do not see the tell-tale peaks at 10kHz and 12kHz. The optical input yielded the same result.

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 H150, with an additional 100ns of 2kHz sinewave jitter injected by the APx555. The telltale peaks at 10kHz and 12kHz can be seen at -100dBFS. 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 H150’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 the filter is of the brickwall-type variety. There are a few low-level aliased image peaks within the audioband at the -110 to -115dBrA level. The primary aliasing signal at 25kHz is highly suppressed and buried in the -145dBrA noise floor.

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 0.05dB. This is a strong result and an indication of a low output impedance, or high damping factor. With a real speaker load, deviations measured roughly the same at 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 72W. The power was varied using the H150’s volume control. The 1 and 10W THD ratios were closely clustered together (within roughly 5dB), and ranged from 0.006% (200-400Hz) to 0.03% (20kHz). At 72W, THD ratios ranged from 0.15% at lower frequencies, up to 0.7% at 20kHz.

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

The chart above shows THD ratios as a function of frequency plots for the MM phono input measured across an 8-ohm load at 10W. The input sweep is EQ’d with an inverted RIAA curve. The THD values for the right channel varied from around 0.4% (20Hz) down to 0.009% (2/3kHz), up to 0.02% at 20kHz. The left channel yielded THD ratios up to roughly 5dB higher than the right channel.

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 H150 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 ratios into 4 and 8 ohms are close (within 5dB), and the left channel outperformed the right by approximately 3dB. The 8-ohm (left) data range from 0.006% at 50mW, down to 0.004% in the 10 to 30W range. The “knee” into 8 ohms can be found right around 50W, while the 4-ohm “knee” can be seen around 75W. The 1% THD marks were hit at 81W and 121W 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 H150 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). The 8-ohm data range from 0.02% at 50mW, down to 0.005% in the 20 to 50W 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 H150 as a function of frequency into three different loads (8/4/2 ohms) for a constant input voltage that yields 20W at the output into 8 ohms (and roughly 40W into 4 ohms, and 80W into 2 ohms) for the analog line-level input. The 8-ohm load is the blue trace and the 4-ohm load the purple trace. We find a small 2-3dB increase in THD from 8 to 4 ohms. These data ranged from 0.006% at 20Hz down to 0.003% at 100-200Hz (8 ohms), then up to 0.03% at 20kHz. The 2-ohm load data was fairly constant at a high 15-20% THD.

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 H150 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 for all three plots are tightly clustered together, which is a strong result, though the absolute THD ratios are not particularly low for a solid-state amplifier. THD ratios range between 0.06% at 20Hz for the two-way speaker (0.02% for the three-way speaker and resistive load), down to between 0.006% and 0.01% between 60Hz and 1kHz, then up to 0.04% 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 H150 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 identical, hovering between the 0.01% and 0.03% 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 H150 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; 0.03% from 40Hz to 250Hz, 0.01-0.02% from 300Hz to 500Hz, and 0.005% from 500Hz to 1kHz.

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 analog XLR line-level input. We see that the signal’s second (2kHz) and third (3kHz) harmonic dominate at roughly -80dBrA, or 0.01%. There are subsequent signal harmonics visible at -90dBrA, or 0.003%, and below. On the right side of the signal peak, we find power-supply-related noise peaks, with the second harmonic (120Hz) dominating at -95dBrA, or 0.002%. Other noise peaks can be seen at and below the -110dBrA, or 0.0003% level.

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 analog RCA line-level input. We see effectively the same result as with the XLR 1kHz FFT above.

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. We see that the signal’s second (2kHz) harmonic dominates at -70/-80dBrA (left/right), or 0.03/0.01%. There are subsequent signal harmonics visible at and below the -90dBrA, or 0.003%, level. On the right side of the signal peak, we find power-supply-related noise peaks, with the primary (60Hz), second (102Hz) and fourth (240Hz) harmonics dominating at between -50dBrA and -60dBrA, or 0.3 to 0.1%. Other noise peaks can be seen at and below the -80dBrA, or 0.01%, level.

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 result is very similar to the analog line-level 1kHz 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. The result is very similar to the 16/44.1 1kHz FFT above, but for a lower noise floor here 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 distinguishable signal harmonics above the -135dBrA noise floor, and power-supply-related noise peaks at -110dBrA, or 0.0003%, and below.

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

Shown above is the FFT for a 1kHz -90dBFS dithered 24/96 input sinewave stimulus at the coaxial digital input, measured at the output across an 8-ohm load. We see the 1kHz primary signal peak, at the correct amplitude, with no distinguishable signal harmonics above the -140dBrA noise floor, and power-supply-related noise peaks at -110dBrA, or 0.0003%, 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 second (100Hz) signal harmonic at -80dBrA, or 0.01%, followed by the third signal harmonic (150Hz) at -90dBrA, or 0.003%. Power-supply-related noise peaks can be seen at -100dBrA, or 0.001%, 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 and 120Hz power-supply-related noise peaks at just above -60dBrA, or 0.1%. The highest signal harmonic is at 100Hz, 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 -90dBrA, or 0.003%, while the third-order modulation products, at 17kHz and 20kHz, are just below the -80dBrA, or 0.01%, level.

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

Shown above is the FFT of the speaker-level output of the H150 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 below the -100dBrA, or 0.001%, 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 -90dBrA, or 0.003%, while the third-order modulation products, at 17kHz and 20kHz, are just below the -80dBrA, or 0.01%, 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 -90dBrA, or 0.003%, while the third-order modulation products, at 17kHz and 20kHz, are just below the -80dBrA, or 0.01%, 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 -70/-80dBrA (left/right), or 0.03/0.01%, while the third-order modulation products, at 17kHz and 20kHz, are just below the -80dBrA, or 0.01%, 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 H150’s slew-rate performance. Rather, it should be seen as a qualitative representation of the H150’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/sharp corners.

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

The final graph above is the damping factor as a function of frequency. We can see damping factors ranging between roughly 200 and 300 for the left channel, and 150 and 200 for the right channel.

Diego Estan
Electronics Measurement Specialist