Network Audio Players/Servers

As discussed in previous lab reports, advanced digital server solutions like Auralic's Aries G1.1 and the partnering G2.1 [HFN Feb '21] typically include a layer of proprietary data conditioning. Grimm Audio's MU1 [HFN Dec '20], the Innuos Statement [HFN Jan '20] and Melco N10 [HFN Jun '19] also include bespoke software. In Auralic's case, the 'conditioning' includes upsampling/downsampling to 2x or 4x the base 44.1kHz/48kHz sample rates in tandem with a choice of four digital filters.

Tested with a Mytek Brooklyn DAC [HFN Aug '17], the 'Precise' option is seen as a very long-tap, linear phase FIR filter that offers the flattest responses (–0.07dB/20kHz with this DAC) and the most complete stopband rejection (up to 130dB) at the expense of extended pre/post 'echoes' in the time domain [see black traces, Graph 1 below]. 'Dynamic' is a related linear phase filter, with fewer taps, offering a similar 130dB stopband rejection and extended response, with minor ±0.002dB ripples, and reduced pre/post echoes [red traces, Graph 1]. The 'Balance' filter option trades 70dB of stopband rejection for a slightly earlier in-band roll-off (–0.1dB/18kHz to –2.3dB/20kHz) and much reduced ringing and group delay in the time domain [blue traces, Graph 1]. The only minimum phase filter, 'Smooth', has no pre-event (acausal) echoes albeit traded for more significant post-event ripples combined with an almost identical HF roll-off/stopband rejection to the 'Balance' option [green traces, Graph 2].

Jitter, tested with three AES/USB DACs [see table, below], is unaffected by choice of digital filter or resampling rate and seems wholly defined by the intrinsic jitter of the (top-flight) DACs themselves. Although the Aries G1.1 lacks the galvanically-isolated USB output of the G2.1 there is no observable deterioration in distortion, S/N or jitter [see Graph 2, below]. PM