Network Audio Players/Servers

The response and time domain behaviour of the ND 555 is entirely determined by Naim's custom 16x upsampling digital filter. This brickwall IIR filter is executed on a 4th-gen SHARC DSP and is combined with two 3rd-order analogue filters (in series to yield a 6th-order roll-off) at the output. This digital filter type suffers no pre-ringing, but does exhibit extended post-ringing [see inset Graph] – akin to a pure analogue filter.

All incoming sample rates are upsampled to one of two elevated base rates – 768kHz (for 48k/96k/192kHz media) and 705.6kHz (for 44.1k/88.2k/176.4kHz media and DSD64 files). The Burr-Brown PCM1704, a legacy 96kHz/24-bit 'ladder type' multibit DAC is used here in current output mode with discrete I-to-V conversion, but its response does not exceed 30kHz with either 96kHz or 192kHz media. Instead, Naim's digital filter cuts in earlier, delivering a 60th-order roll-off at –3dB/27kHz. PM.