Headphones

The response and time domain behaviour of the Uniti Atom's digital heart is entirely determined by Naim's custom 16x upsampling digital filter. This brickwall IIR filter is executed on a SHARC DSP and is combined with two series-connected 3rd-order analogue filters (6th-order roll-off) at the output. In common with the proprietary WTA filter used in Chord Electronics' DACs, Naim's bespoke filter cannot be adapted to accommodate MQA, should either company have been inclined to offer this facility in the first place. Specifically, Naim's digital filter avoids acausal pre-ringing, but does exhibit extended post-ringing [see inset Graph].

The partnering Burr-Brown PCM1791, a legacy 'Advanced Segment' DAC, operates up to 192kHz/24-bit and DSD64, but its response here 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