MEASUREMENTS

measured the Masters Series M10 using my Audio Precision SYS2722 system (see the January 2008 “As We See It”). As the NAD is a class-D design, I didn’t run my usual preconditioning test of using the amplifier to drive a 1kHz tone at one-third power into 8 ohms. Nevertheless, before doing any testing I ran it for an hour at a moderate power level, to ensure that it was fully warmed up. Because class-D amplifiers emit relatively high levels of ultrasonic noise that would drive my analyzer’s input into slew-rate limiting, all measurements were taken with Audio Precision’s auxiliary AUX-0025 passive low-pass filter, which eliminates noise above 200kHz. Without the filter, there was 250mV of ultrasonic noise present at the loudspeaker terminals, which is