Network Audio Players/Servers

Thanks to Lumin's balanced analogue output stage and custom digital processing, the performance of the D2 is not wholly determined by its choice of Cirrus Logic (née Wolfson) WM8741 DAC, albeit one per channel. Maximum output is a healthy 4.1V from a usefully low 10ohm source impedance while the A-wtd S/N ratio is a very wide 115dB, via both network and USB-A inputs and over all sample rates. Distortion is very low too with a minimum of 0.0003-0.0006% achieved between 20Hz-20kHz at its peak output [see Graph 1, below]. This is unusual these days when most DACs typically enjoy their lowest THD from –10dBFs to –20dBFs, but is testament to the quality of the analogue stage as much as the legacy WM8741 DAC(s). The latter is limited to 192kHz but will handle DSD64 either natively or in a 'DSD Plus' mode where the bitstream is converted to LPCM. The DAC also offers a range of advanced digital filters although, in the D2, a standard, sharp-roll linear phase filter is employed for the lower (44.1kHz/48kHz) input sample rates. Stopband rejection is an almost absolute 122dB here while the frequency response shows a very mild treble lift of +0.1dB/20kHz.

Higher 96kHz/192kHz sample rates have a slightly earlier roll-off than anticipated at –3dB/42kHz and –3dB/50kHz, respectively, although the rejection of alias images is no less impressive than with the lower 44.1kHz/48kHz rates. Jitter is very low too though, once again, this shows some difference with increasing sample rate – from a vanishingly low 15psec at 48kHz to 50-55psec with 96kHz/192kHz inputs. In all cases the level of phase noise or noise-like jitter is almost entirely eliminated [see Graph 2, below] which typically bodes well for stable, pin-sharp stereo images. Crosstalk is also very low at <–100dB. PM