Headphones

As every generation of iFi Audio's various product lines gives way to the next there is typically a marked evolution in performance, and so it is between the NEO iDSD and the mk2 reviewed here. Tested in fixed, balanced line output guise, the premature clipping reported in the mk1 has been fixed in the mk2 by iFi Audio reducing the maximum output from 5.6V to 4.3V - all achieved without comprising the wide 110dB A-wtd S/N ratio or excellent low-level linearity that holds true to within ±0.2dB over a full 110dB dynamic range. The mk1 also showed a complex pattern of jitter sidebands at ±33Hz, ±66Hz, ±99Hz, etc, amounting to some 550psec and this, again, has been addressed in the NEO iDSD 2 which incurs a mere 10-15psec of correlated jitter with any of its upsampling filters [black spectrum, Graph 2]. Some phase noise remains but only the 'Bit Perfect' mode shows any real increase in both requantisation noise and ~200psec of correlated jitter [red spectrum, Graph 2].

The TI DSD1793 DAC and option of four user-selectable digital filters is retained in the NEO iDSD 2 with the 'STD' (linear phase) choice offering the best (53dB) stopband rejection and flattest -0.14dB/20kHz, -0.75dB/45kHz and -2.6dB/90kHz responses with 48kHz, 96kHz and 192kHz media, respectively. The remaining filters offer poor stopband rejection and a greater HF roll-off traded for reduced time domain distortion with BP (Bit Perfect) best suited to higher sample rate media. Improvements to the analogue output are reflected in its reduced 0.0009-0.002% peak level distortion (re. 0dBFs, 20Hz-20kHz), falling to a minimum of 0.0001-0.00015% over the top 20dB of its dynamic range [see Graph 1, below]. For a full reveal of the NEO iDSD 2's headphone amplifier performance, see our boxout. PM