May 2006
NAD C372
Integrated Amplifier: Measurements
All amplifier measurements are performed
independently by BHK Labs. Please click to learn
more about how we test amplifiers there. All measurement data, including graphical
information displayed below, is the property of SoundStage! and Schneider
Publishing Inc. Reproduction in any format is not permitted.
 Measurements were made at 120V AC line voltage with both
channels being driven; measurements made on left channel unless otherwise noted. The
volume control was set to the reference position to produce 5W into 8 ohms with 500mV
input unless otherwise noted.
 This integrated amplifier does not invert polarity with or
without tone controls engaged.
 AC line current draw:
 at idle: 0.59A
 in standby: 0.04A
 Input sensitivity for 1W output into 8 ohms, volume at
maximum: 35.0mV
 Output impedance at 50Hz: 0.035 ohms
 Gain, output voltage divided by input voltage, volume at
maximum: 80.8X, 38.2dB
 Output noise, 8ohm load, 1kohm input termination, Lch/Rch
 Volume control at reference position
 wideband: 0.40mV, 77.0dBW / 0.37mV, 77.7dBW
 A weighted: 0.11mV, 88.2dBW / 0.078mV, 91.2dBW
 Volume control full clockwise
 wideband: 0.62mV, 73.2dBW / 0.54mV, 74.4dBW
 A weighted: 0.14mV, 86.1dBW / 0.095mV, 89.5dBW
 Volume control full counterclockwise
 wideband: 0.38mV, 77.4dBW / 0.34mV, 78.4dBW
 A weighted: 0.058mV, 93.8dBW / 0.089mV, 90.0dBW
Power output with 1kHz test signal
 8ohm load at 1% THD: 189W
 8ohm load at 10% THD: 228W
 4ohm load at 1% THD: 185.5W
 4ohm load at 10% THD: 228.7W
General
The NAD C372 is a mediumpower solidstate integrated
amplifier. Overall gain of the unit is about normal for an integrated amplifier. Of
interest, and not always the case, is that the overall input/output polarity is maintained
as noninverting when the tone controls are engaged.
Chart 1 shows the frequency response of the amp with
varying loads. The highfrequency response is quite wide. with an approximate 3dB down
point of 200kHz. Output impedance, as judged by the closeness of spacing between the
curves of opencircuit, 8ohm, and 4ohm loading, is quite low in the audio band. The
usual NHT dummyload curve is not shown as the variations in the response would not show.
The variation with the NHT dummy load in the audio range is of the order of +/0.05dB  a
negligible amount. The frequency response was quite independent of volumecontrol setting.
Chart 2 illustrates how total harmonic distortion plus
noise vs. power varies for 1kHz and SMPTE IM test signals and amplifier output load.
Unusual for a solidstate power amplifier, the attainable power is about the same for 4
and 8ohm loads. Amount of distortion is low right up to clipping – the behavior of
most solidstate power amplifiers.
Total harmonic distortion plus noise as a function of
frequency at several different power levels is plotted in Chart 3. Amount of rise in
distortion at low and high frequencies is low except at the lowfrequency extremes at the
150W level where the power supply just can’t supply the steadystate power in the
4ohm loads. This didn’t happen with the 8ohm loads.
Damping factor vs. frequency is shown in Chart 4 and is of
a value and nature typical of many solidstate amplifiers being high up to about 1kHz and
then rolling off with frequency.
A spectrum of the harmonic distortion and noise residue of
a 10W 1kHz test signal is plotted in Chart 5. The magnitude of the ACline harmonics are
low and simple, and intermodulation components of line harmonics with signal harmonics are
also low. Signal harmonics consist of a tapering off spectrum of even and odd harmonics.
Chart 1
 Frequency Response of Output Voltage as a Function of Output Loading 
Red line: open circuit
Magenta line: 8ohm load
Blue line: 4ohm load
Chart 2  Distortion as a Function
of Power Output and Output Loading 
(line up at 10W to determine lines)
Top line: 4ohm SMPTE IM
Second line: 8ohm SMPTE IM
Third line: 4ohm THD+N
Bottom line: 8ohm THD+N
Chart 3  Distortion
as a Function of Power Output and Frequency 
4ohm output loading
Cyan line: 150W
Blue line: 70W
Magenta line: 10W
Red line: 1W
Chart 4  Damping Factor
as a Function of Frequency 
Damping factor = output impedance divided into 8
Chart 5  Distortion and
Noise Spectrum 
1kHz signal at 10W into a 4ohm load
