Measurement by Rohde & Schwarz UPV audio analyser

MEASURED PERFORMANCE

Frequency response measured flat to 21kHz with a 44.1kHz sample rate CD signal; there is no roll off or peaking. The same result was obtained with 96kHz sample rate. With a 192kHz sample rate test signal anti-alias filters imposed a peak above 50kHz, seen in our analysis, but subjectively this is unlikely to be consequential. The M51 will have an even tonal balance in use, or may have some sheen.

    Distortion levels were on the high side with CD (16bit/44.1kHz sample rate) measuring 0.4% at -60dB with a 997Hz tone, where 0.2% is possible. With 24bit resolution the M51 was incredibly linear, distortion measuring just 0.012% at -60dB (96kHz sample rate). Similarly, EIAJ Dynamic Range was mediocre with CD, measuring 100.5dB where 102dB is expected, but 110dB with 24/96.
    Noise was low at -123dB at 0dB, quantisation noise raising the figure to -100dB with 16bit and -111dB with 24bit, when using a -60dB test tone, notched out to lift digital-zero muting. These levels are inaudible of course.
    Output was a high 4.8V from the balanced XLR sockets and  2.4V from unbalanced phono outputs.
    The M51 produces a good set of results, interestingly different from other DACs. It is unusually linear, as linear as DSD from SACD,  and should give a silky sound. NK

Frequency response (-1dB)
    1Hz - 96kHz

Distortion (16/24bit)    %
0dB                           0.01
-60dB                       0.4 / 0.012
Separation (1kHz)      112dB
Noise (IEC A)            -123dB
Dynamic range (16 / 24bit)    100/110dB
Output                     4.8 / 2.4V

FREQUENCY RESPONSE (24/192)

DISTORTION  (16bit, 44.1kHz)