Naim Audio ND5 XS 2 Network-Attached DAC Lab Report

Lab Report

While the ND5 XS 2's PCM1791A DAC-based analogue output is simpler in execution than Naim's PCM1792A-based NDX 2 [HFN Sep '18], its digital inputs are processed via the same upsampling/jitter-suppressing 40-bit code. It's so effective there's no significant difference in performance whether data is delivered via S/PDIF, USB-A or (wired) network connections. The fixed analogue output offers a maximum 2.22V from a low 23ohm source impedance (increasing to 190ohm at 20Hz) and incurs a mere 0.0002-0.0095% distortion (20Hz-20kHz, 0dBFs), falling to a minimum of 0.0002-0.00085% over the top 30dB of its dynamic range [see Graph 1, below]. The A-wtd S/N is a few dB behind the NDX 2 at 105.6dB and its low-level linearity is true to ±0.3dB over a 100dB dynamic range (±0.6dB over 110dB).


Distortion versus 48kHz/24-bit digital signal level over a 120dB dynamic range via S/PDIF/USB/network (1kHz, black; 20kHz, blue)


Time (red) and magnitude (black) responses with 192kHz data

The response and time domain behaviour of the ND5 XS 2 is entirely determined by Naim's custom brickwall IIR filter which is combined with a gentle 6th-order analogue filter at the output. This digital filter type suffers no pre-ringing, but does exhibit extended post-ringing [see Graph 2, above] and, therefore, no acausal distortion – just like a pure analogue filter. This filter acts earlier than is typical, and trades a reduced attenuation of stopband artefacts immediately adjacent to the top-end of 48kHz music media (just –43.1dB at 26kHz re. 22kHz) while restricting the response of both 96kHz and 192kHz digital audio to a –3dB point of 29kHz. Lower 44.1kHz/48kHz sample rates have an insignificant –0.3dB roll-off at 20kHz. Jitter suppression, meanwhile, is not only superior to that observed with the NDX 2 but defines the current state-of-the-art at <10psec with 48kHz/24-bit inputs and ~15psec at higher sample rates. PM

Maximum output level / Impedance 2.21Vrms / 23-190ohm
A-wtd S/N ratio (S/PDIF / USB-A) 105.6dB / 105.5dB
Distortion (1kHz, 0dBFs/–30dBFs) 0.00065% / 0.00028%
Distortion & Noise (20kHz, 0dBFs/–30dBFs) 0.0095% / 0.0009%
Freq. resp. (20Hz-20kHz/30kHz) +0.0 to –0.28dB/–8.1dB
Digital jitter (48kHz / 96kHz) <10psec / 15psec
Resolution @ –110dB (S/PDIF / USB) ±0.6dB / ±0.6dB
Power consumption 10W (1W standby)
Dimensions (WHD) / Weight 432x70x301mm / 6.6kg
Price £2299

Naim Audio Ltd
Supplied by: Naim Audio Ltd
01722 426600