Network Audio Players/Servers

While the NEO Stream takes its industrial cues from the NEO iDSD [HFN Mar '21], and shares the same XMOS processor and TI DSD1793 DAC, the interim has seen iFi Audio address the only technical foibles detailed in my Lab Report of two years ago. Specifically, peak-level 0dBFs inputs no longer clip the analogue output which now achieves a 'clean' 2.08V (single-ended) from a uniform 37ohm source impedance. Also, the complex jitter pattern with sidebands at ±33Hz, ±66Hz, ±99Hz... amounting to some 550psec, has now been eliminated. Via its USB-A input, an external HDD and with 32MB buffering, the NEO Stream achieves a fabulously low 5psec and 12psec with 48kHz and 96kHz/24-bit files, increasing to 250psec jitter with 192kHz files, the latter almost entirely PSU-related. The 0.0016-0.035% distortion (20Hz-20kHz) is a little higher at HF than with the NEO iDSD's balanced output, but the 0.0005-0.0056% minimum achieved by the NEO Stream at –20dBFs [see Graph 1, below] is still very good. As, I might add, is the 105dB A-wtd S/N ratio.

If the NEO iDSD was limited to iFi Audio's GTO (Gibbs Transient Optimised) digital filter by default, the NEO Stream offers Standard (linear phase), GTO (minimum phase), Minimum (actually a short linear phase filter!) and 'Bit Perfect' (NOS filter) options via its menu. The Standard and GTO filters deliver the flattest responses (–0.1dB and –0.45dB/20kHz, respectively) and good stopband rejection (106dB and 53dB) at the expense of added ringing in the time domain [black and blue traces, see Graph 2]. By contrast, the Minimum and BP filters [red and green traces] have little or no ringing but trade this for poorer stopband rejection and a more obviously rolled-off treble with low sample rate files (–3.1dB and –3.2dB/20kHz). PM