NAD M32 digital amplifier Lab Report

Tested via its analogue line input, power output, and distortion, rather depend on the position of the volume control because the input ADC (sampling at 48kHz-192kHz/24-bit) clips before the output. At a volume setting of –6.0dB distortion is 0.006% (very close to NAD's specification) but at a volume setting of 0.0dB distortion rises to 0.012%, and at +6.0dB it's 0.025% (all for the same 1kHz/1W/8ohm output). However, with the volume at –6.0dB the maximum power output is just 2x50W/8ohm, while at 0.0dB it is 2x190W into both 8/4ohm (with the 'speaker compensation' set to 8 or 4ohm). While the amplifier is clearly protected against high continuous power outputs into lower impedances, its dynamic output (in traditional NAD style) is generous at 200W and 400W into 8/4ohm loads with a current-protected 433W/167W into 2/1ohm loads [see Graph 1].


Dynamic power output versus distortion into 8ohm (black trace), 4ohm (red), 2ohm (blue) and 1ohm (green) speaker loads. Max. current is 14.7A


THD vs. digital level over a 120dB range at 1kHz (black) and 20kHz (blue). 0dBFs = 190W/8ohm

In practice the M32 is far better optimised for its digital MDC card where a maximum 2x182W/8ohm is achieved with a peak level 0dBFs digital input and with the volume set to –0.5dB. The amplifier clips at 0.0dB (200W/8ohm at 1% THD) so the volume control should never be advanced beyond this point. The digital input frequency response(s) scale with input sampling rate reaching +0.1dB/20kHz, +2.9dB/45kHz and –8dB/90kHz with 48kHz, 96kHz and 192kHz media, respectively. Distortion (plus noise) is typically <0.01% through bass and midrange frequencies over the top 50dB of its dynamic range [black trace, Graph 2] but increases steeply above 10kHz-20kHz as a result of the modulator's ultrasonic requantisation noise [blue trace]. Jitter is impressive low at 260-300psec from 1-10W output at all incoming sample rates. PM

Continuous power (<1% THD, 8/4ohm): 190W / 190W
Dynamic power (<1% THD, 8/4/2/1ohm): 200W / 400W / 433W / 167W
Output impedance (20Hz–20kHz): 0.005–0.20ohm
Freq. resp. (20Hz–20kHz, 45kHz, 90kHz): –0.2 to +0.1dB / +2.9dB / –7.8dB
Digital jitter (48kHz/96kHz, 0dBW): 262psec / 300psec
A-wtd S/N ratio (re. 0dBW/0dBFs): 84.8dB (Analogue) / 107.2dB (Dig)
Dist. (20Hz-20kHz; 0dBW/–20dBFs) : 0.009-0.27% / 0.002-0.22%
Power consumption (idle/rated o/p): 37W / 400W (4W standby)
Dimensions (WHD) / Weight: 435x133x396mm / 9.8kg
Price: £3499

NAD Electronics International
Supplied by: Sevenoaks Sound and Vision, UK
01732 459555