Network Audio Players/Servers

All streaming/DAC products equipped with (a well-implemented) ES9038PRO-based digital section will show very low noise, a wide S/N ratio and low correlated jitter, and NAD's Masters M66 is broadly illustrative of this trend. Although the DAC hardware comes with the option of six different digital filters NAD has had the good sense to choose one - the 'fast' minimum phase type - and 'voice' the M66 accordingly. This filter offers a moderate 67dB stopband rejection with no acausal 'pre-echo'/time domain distortion on transients, and very flat responses that reach out to -0.03dB/20kHz, -0.10dB/45kHz and -0.21dB/90kHz with 48kHz, 96kHz and 192kHz inputs, respectively. Low-level resolution is true to ±0.15dB over a full 110dB range thanks to the 5.04V peak-level output and very generous 117.5dB A-wtd S/N ratio, all from a 21ohm balanced/XLR source impedance. Distortion settles out at 0.00013%/1kHz at peak level (re. 1kHz) falling to a minimum of 0.00008%/1kHz and 0.0004%/20kHz over the top 20dB of its dynamic range [see Graph 1, below].

Jitter is fabulously low at <12psec (PSU-induced) with 24-bit inputs across all sample rates but while correlated sidebands are well suppressed (a feature of all ESS Sabre DACs) there is evidence of clock phase noise in the low-level/low-frequency 'skirt' [see Graph 2, below, with x10 zoomed freq. bandwidth in grey]. This remains at a very low level, however. Finally, it's worth noting that the analogue inputs are digitised at 96kHz via an ES9822PRO ADC yielding a maximum +8.5dB gain and -0.5dB/34kHz to -3dB/40kHz response which then reduces to a gain of +2.7dB but a wider 2Hz-100kHz (±0.1dB) response and 99.6dB A-wtd S/N ratio (re. 0dBV) in 'Analogue Direct' mode. PM

Above: Distortion versus 48kHz/24-bit digital signal level over a 120dB dynamic range (black, 1kHz; blue, 20kHz). Note extended 0-140dB Y (distortion) scale