Network Audio Players/Servers

In common with the predecessor Aries G2.1 [HFN Feb '21], Auralic's Aries G2.2 is not only a network-attached music storage device but also includes a deal of proprietary signal conditioning. This takes the form of upsampling and/or downsampling up to 8x the base 44.1kHz/48kHz sample rates to a maximum of 384kHz and DSD1024, depending on how the USB interface reports the capability of the attached DAC back to the Aries G2.2. Numerous digital filter algorithms are embedded in the code, many tied to a specific sample rate, and these are broadly represented as four user-selectable options. Comprehensively re-tested here with the Mytek Brooklyn DAC [HFN Aug '17], the Aries G2.2 shows no substantive difference in filter performance over the G2.1 – 'Precise' remains a very long-tap, linear phase FIR filter that offers the flattest responses (–0.07dB/20kHz) and best stopband rejection (up to 132dB) at the expense of extended pre/post 'echoes' in the time domain [black traces, Graph 1]. 'Dynamic' and 'Balance' are also linear phase filters albeit with reduced taps/ringing, traded for 130dB/71dB stopband rejection and in-band cut-offs of –0.8dB and –2.3dB/20kHz [red and blue traces, respectively]. The only minimum phase filter, 'Smooth', has no acausal echoes, a 71dB stopband rejection and almost identical HF roll-off to the 'Balance' option [green traces, Graph 2].

Jitter, tested with four USB DACs, is unaffected by choice of digital filter. AudioQuest's DragonFly [HFN Mar '14] enjoyed a halving of jitter from 300psec (PC interface) to 131psec [see Graph 2] while the repeating ±33/66Hz/99Hz sidebands seen from iFi Audio's NEO iDSD [HFN Mar '21] were reduced from 550psec to just 6psec here. Finally, both the dCS Vivaldi One APEX and Mytek DACs provide full galvanic isolation/onboard reclocking, so very little difference in their inherent ~10psec jitter was detected. As usual, budget/hub-powered DACs are seen to benefit the most. PM