Advance Paris X-i75 Integrated Amplifier Measurements

Link: reviewed by Thom Moon on SoundStage! Access on February 1, 2025

General Information

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

The Advance Pari X-i75 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 X-i75 offers seven sets of line-level analog inputs (RCA), one moving-magnet (MM) phono input (RCA), two digital S/PDIF coaxial (RCA) inputs, one digital S/PDIF optical (TosLink) input, one USB digital input, left/right pre-outs (RCA), and rec-outs (RCA), one sub-out (RCA), one set 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 (RCA) line-level, and phono, as well as 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 rated 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.

The X-i75 also offers a Hi Bias (for high bias) switch on the rear panel. No appreciable differences (THD, noise, gain) were seen with this switch in the on or off position; however, comparative FFTs can be found in this report. Unless otherwise stated, the high-bias switch was left in the off position because slightly lower levels of odd-ordered signal harmonics were observed in this configuration.

Based on the accuracy and randomness of the left/right volume channel matching (see table below), the X-i75 volume control is digitally controlled but operating in the analog domain. The X-i75 overall volume range is from -51dB to +38dB (line-level input, speaker output). It offers 2dB increments from positions 1 to 30, and 1dB increments from positions 31 to 60.

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 Advance Paris for the X-i75 compared directly against our own. The published specifications are sourced from Advance Paris’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 X-i75 was able to sustain 120W into 4 ohms (~3% THD) using an 80Hz tone for 500ms, alternating with a signal at -10dB of the peak (12W) for 5 seconds, for 5 continuous 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 X-i75 was 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 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 X-i75 is close to flat within the audioband (20Hz to 20kHz, -0.3/-0.1dB). The -3dB point is at roughly 150kHz, and -2.5dB at 5Hz. The X-i75 appears to be AC 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 (8-ohm loading, line-level input, bass and treble controls at maximum and minimum)

Above are the frequency-response plots (relative to 1kHz) measured across the speaker outputs at 10W into 8 ohms, with the bass and treble controls set to minimum and maximum. We find roughly +/-8.5dB of bass boost/cut centerd at 100Hz, and +/-8.5dB of treble boost/cut at 20kHz.

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

Above are the phase-response plots from 20Hz to 20kHz for the line-level input, measured across the speaker outputs at 10W into 8 ohms. The X-i75 yielded only about +20 degrees of phase shift at 20Hz, and at worst -10 degrees at 20kHz.

Frequency response (8-ohm loading, subwoofer output)

Above is the frequency-response plot (relative to 20Hz) measured at the line-level subwoofer output. We find an essentially perfectly flat response down to 5Hz (-0.2dB), a -3dB point at 200Hz, and a 9dB/octave high-frequency roll-off.

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

The chart above shows the frequency response for the MM phono input. What is shown is the deviation from the RIAA curve, where the input signal sweep is EQ’d with an inverted RIAA curve supplied by Audio Precision (i.e., zero deviation would yield a flat line at 0dB). We see deviations as large as +0.5dB (30Hz and 20kHz) and -0.4dB (200Hz) within the audioband. We also see what appears to be the implementation of a rumble filter (-3dB at 8Hz).

Phase response (MM input)

Above is the phase response plot from 20Hz to 20kHz for the MM phono input, measured across the speaker outputs at 10W into 8 ohms. The X-i75 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 +20 degrees at 20Hz and -80 degrees at 20kHz.

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

The chart above shows the X-i75’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, and 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 similar results as the analog response (between -2.5 and -3.5dB at 5Hz). The -3dB points are: 21kHz for the 16/44.1 data, 46.5kHz for the 24/96, 93kHz for the 24/192 data, and 150kHz for the analog input. Also of note, all digital frequency responses exhibit brickwall-type behavior around their respective high-frequency cut-offs.

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 X-i75, 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 -110dBFS down to 0dBFS, with the exception of the right channel at 24/96, which was -9dB down at -110dBFS.

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 X-i75. 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 X-i75 where 0dBFS is set to 2Vrms. 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.

Here we see a poor J-Test result, with an elevated noise floor (-120dBFS) around the main 12kHz signal peak, and peaks at -120dBFS flanking the main signal peak. This is an indication that the X-i75 DAC may have poor 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 X-i75. The optical input yielded similar results 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 X-i75, with an additional 10ns of 2kHz sinewave jitter injected by the APx555. The telltale peaks at 10kHz and 12kHz can easily be seen at -70dBFS. More evidence of the poor jitter immunity. The optical input showed a similar 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-evel output of the X-i75, with an additional 100ns of 2kHz sinewave jitter injected by the APx555. The telltale peaks at 10kHz and 12kHz can be seen at a higher -50dBFS. The optical input show a similarly poor 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 X-i75’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 implementation of a brickwall-type filter. There are no visible low-level aliased image peaks within the audioband; however, there is a rise in the noise floor around the signal peak up to -110dBFS. The primary aliasing signal at 25kHz is highly suppressed at -85dBrA, while the second and third distortion harmonics (38.2, 57.3kHz) of the 19.1kHz tone are near the same level.

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 see that the deviations between no load and 4 ohms are at roughly 0.25dB. This is a poor result for a solid-state amp and an indication of a relatively high output impedance, or low damping factor. With a real speaker load, deviations measured lower at roughly 0.2dB.

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 X-i75’s volume control. The 1 and 10W THD ratios were similar, ranging from as low as 0.001% (right channel) from 60 to 400Hz, and up to 0.03% (left channel) at 20kHz (the right channel was at 0.015%). At 65W, THD ratios were higher (0.009%) and relatively flat across most of the audioband (20Hz to 2kHz), then up to 0.03% (left channel) at 20kHz (the right channel was at 0.015%).

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

The chart above shows THD ratios as a function of frequency plots for the MM phono input measured across an 8-ohm load at 10W. The input sweep is EQ’d with an inverted RIAA curve. The THD values for the MM configuration vary from around 0.2% (20Hz) down to 0.002% (300-500Hz), up to 0.03% (left channel) at 20kHz (the right channel was at 0.015%).

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 X-i75 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 vary by about 5dB, the same as between channels (the right channel and 8-ohm data yielded lower THD ratios). They range (for the right channel into 8 ohms) from 0.005% at 50mW, down to 0.0015% in the 1 to 5W range, with the “knee” at 0.007% just past 60W, while the 4-ohm knee can be seen at 0.02% just shy of 100W. The 1% THD marks were hit right at the rated levels of 75W and 110W 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 X-i75 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 remarkably close (with 2-5dB). They range from 0.03% at 50mW, down to 0.003% (right channel, 8 ohms) in the 10W 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 X-i75 as a function of frequency into three different loads (8/4/2 ohms) for a constant input voltage that yields 10W at the output into 8 ohms (and roughly 20W into 4 ohms, and 40W into 2 ohms) for the analog line-level input. The 8-ohm load is the blue trace, the 4-ohm load the purple trace, and the 2-ohm load the pink trace. We find a roughly 10dB increase in THD from 8 to 4 to 2 ohms. These ranged from 0.002% at 20Hz to 400Hz, then up to 0.03% at 20kHz for the 8-ohm load. The 4-ohm load ranged from 0.005% at 20Hz to 400Hz, then up to 0.06% at 20kHz. The 2-ohm load ranged from 0.015% at 20Hz to 400Hz, then up to 0.1% 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 X-i75 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 0.2% at 20Hz for the two-way speaker versus 0.005% for the resistive load, and 0.05% at 20kHz into the three-way speaker versus 0.03% for the resistive load. Between the important frequencies of 500Hz to 6kHz, all three THD traces were close, with lower THD ratios into the real speakers (0.001-0.003%) compared to the dummy load (0.002-0.01%).

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

The chart above shows intermodulation distortion (IMD) ratios measured at the output of the X-i75 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 across the sweep. Most of the IMD results are hovering around the 0.003-0.005% 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 X-i75 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 (the three-way speaker was up to 5dB higher than the two-way speaker and resistive load), between 0.007% and 0.015% 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) harmonic dominates at roughly -90dBrA, or 0.003%, while the third (3kHz) and fourth (4kHz) harmonics can be seen at -100dBrA, or 0.001%. Higher-order harmonics are also visible at lower levels. On the right side of the signal peak, we find power-supply-related noise peaks, with the first (60Hz) and third (180Hz) harmonics dominating at -100dBrA, or 0.001%, for the left channel, and -110dBrA, or 0.0003%, for the right channel. Overall, the noise from the left channel is roughly 10dB higher than the right channel. High-order power-supply-related noise peaks can be seen from the left channel up to nearly 10kHz.

FFT spectrum – 1kHz (line-level input, Hi Bias turned on)

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, with Hi Bias turned on. The results are very similar to the FFT above without Hi Bias on. The differences are in the high odd-ordered signal harmonics (5kHz, 7kHz), which are about 10dB higher with Hi Bias on.

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 harmonics, while difficult to distinguish amongst the power-supply related noise peaks, are similar in amplitude as seen in the analog line-level FFT above. Power-supply-related noise peaks dominate throughout the audioband, ranging from -55dBrA, or 0.2%, at 60Hz, down to the -120dBrA, or 0.0001%, 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. Results are very similar to the analog FFT above within the audioband.

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 slightly 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, and powers-supply-related noise peaks (mostly from the left channel) 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 signal harmonics above the -140dBrA noise floor, and power-supply-related noise peaks (mostly from the left channel) 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 -95dBrA, or 0.002%. Other peaks (both signal harmonics and power-supply noise-related harmonics) can be seen at -100dBrA 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 noise peaks at -55dBrA and -65dBrA, or 0.2% and 0.02%, respectively. Signal harmonics are much lower, at the -90dBrA, or 0.003%, level and below.

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

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

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

Shown above is the FFT of the speaker-level output of the X-i75 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 -110dBrA, or 0.0003%, 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 around -105dBrA, or 0.0006%, while the third-order modulation products, at 17kHz and 20kHz, are lower at -110dBrA, or 0.0003%.

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

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sinewave stimulus tone measured at the output across an 8-ohm load at 10W for the digital coaxial input at 16/44.1 (-1dBFS). We find that the second-order modulation products (i.e., the difference signal of 1kHz) are 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, 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 products (i.e., the difference signal of 1kHz) are at -90dBrA, or 0.003%, while the third-order modulation products, at 17kHz and 20kHz, are at the same 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 X-i75’s slew-rate performance. Rather, it should be seen as a qualitative representation of the X-i75’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 softening or 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 of around 60 through most of the audioband. This is a mid-tier result for a medium-powered integrated solid-state amplifier.

Diego Estan
Electronics Measurement Specialist