NAIM ND5 XS/XP5 XS (£1925/£1595)

摘要

If there's one technical feature that defines the performance - and sound - of the ND5 XS then this is the proprietary upsampling MR filter first seen in the Nairn DAC [HFN Jun ' 10]. This custom digital filter acts earlier than is typical, providing reduced attenuation of stopband artefacts immediately adjacent to the top-end of 48kHz recordings (just -43dB at 26kHz re. 22kHz) and restricting the response of both 96kHz and 192kHz digital audio to a -3dB point of 27kHz [see Graph 2, below]. Lower 44.1kHz and 48kHz sample rates feature a -0.25dB roll-off at 20kHz. The decision to employ such a filter is a subjective judgement on the part of Nairn's engineers but the elimination of all pre-ringing is clearly revealed by the impulse response [inset. Graph 2]. The closest digital parallel is with Cambridge Audio's apodising filter [HFN Aug' 11 ] and with the analogue filter developed by Soshin Electric for Sony's inaugural CDP-101 CD player 30 years ago [HFN Jan '12, p112]. Unlike the Nairn DAC, however, distortion increases more obviously at high frequencies through the ND5 XS's analogue stage from 0.001* to 0.01%, a factor of lOx evidenced in the black (1kHz) and blue (20kHz) traces on Graph 1, below. The A-wtd S/N is about 2-3dB poorer than the Nairn DAC at 106dB but linearity is unchanged at ±0.1 dB over a full lOOdB dynamic range. Stereo separation is superb at > 110dB from 20Hz-20kHz while jitter is fabulously low at <20psec over all sample rates [see Graph, HFN Feb' 12, p61 ]. Readers are invited to view a QC Suite report for the Nairn ND5 XS's digital audio performance by navigating to www.hlfinews.co.uk and clicking on the red 'download' button.