Network Audio Players/Servers

As we saw in the Ovation CS 8.2 [HFN May '17], which employed an earlier generation of Pascal's S-PRO2 Class D amp module, AVM's 500W/4ohm rating amounts to 2x245W/8ohm and 2x480W/4ohm in practice, with 240W, 510W and 830W achievable under dynamic conditions into 8, 4 and 2ohm loads [see Graph 1, below]. The modules are current-protected and so output into low (1ohm) loads is 'limited' to 380W (20.4A at <1% THD). The A-wtd S/N is a little below average at 78.4dB (re. 0dBW) but the response, which rolls gently away from –1dB/12kHz to –2.6dB/20kHz, takes the edge off any glare. The pattern of distortion, low at 0.007-0.009% through bass and midrange, increases more rapidly at HF to 0.03%/10kHz and 0.06%/20kHz (all re. 0dBW). Versus level, THD increases gently from 0.007%/1W to 0.02%/10W, 0.05%/100W and 0.1%/200W.

While these qualities are primarily linked to the Class D amp, the CS 8.3's preamp also picks up some slight 'colour' from the triode tube stage [see Graph 2] so that THD falls from 0.014-0.0013% over the top 30dB of the ES9018 DAC's dynamic range (the ES9038 claimed in AVM's literature is incorrect). However, with gain set to '+4' for a 2.03V preamp output, the 106.1dB A-wtd S/N ratio remains very respectable. The 'Steep' and 'Smooth' digital filters are both linear phase types, the former trading more extensive ringing for a full 83dB stopband rejection and flatter –1.3dB/20kHz, –5.5dB/45kHz and –13.6dB/90kHz response with 48kHz, 96kHz and 192kHz media. The 'Smooth' filter offers just 6dB of stopband rejection and a 'sweeter' –4.3dB/20kHz response, but ringing/time domain distortions are much reduced. It is recommended for 96kHz+ sample rates. PM