Cambridge Audio EXA100 Integrated Amplifier Measurements

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