Pro-Ject Stream Box S2 Ultra network bridge Lab Report

The Pro-Ject Stream Box S2 Ultra, like the Roon Nucleus+ [HFN May ’18], and Melco N1ZS20/2 [HFN Jun ’17], N1ZS10 [HFN Feb ’15], N1AH40 [HFN Aug ’15] and N1ZH60 [HFN Jun ’16], is a transcoding/signal conditioning device so any uplift in performance – over a conventional NAS or PC/Mac – can only be inferred via a third-party player or DAC. The jitter suppression and/or galvanic isolation of the attached USB DAC is a factor here, so a DAC with excellent data recovery/reclocking may not express a significant difference. Similarly, a DAC that incurs jitter at the chip level will suffer the same jitter sidebands in the analogue domain regardless of the coherence of the digital data.

For my tests I used the Pro-Ject Play app to set the buffer to 12MB (max) with a pre-buffer of 40% and resampling ‘off’. Driven via the Stream Box S2 Ultra’s ‘USB DAC’ output, the AC-powered Oppo Sonica DAC [HFN Oct ’17] still showed a low-rate skirt of uncorrelated jitter – the cause inside the Sonica itself. A PC-to-Sonica USB connection yielded 155psec, falling to 114psec via the Melco N1ZS20/Sonica [black spectrum, Graph 1] and traded here for a more complex pattern at a lower 112psec [red].


48kHz/24-bit jitter spectra from an Oppo Sonica DAC over USB (black, via Melco N1ZS20/2 USB player out; red, via Pro-Ject Stream Box S2 Ultra


48kHz/24-bit jitter spectra from a Chord Mojo over USB (red, via standard PC; black, via Stream Box S2 Ultra; cyan, via Melco N1ZS20/2 USB player out)

Hub-powered USB DACs often provide a good indication of incoming data integrity and noise on the +5V supply, and here iFi Audio’s iDSD DAC showed a drop in jitter from 140psec to 11psec coupled with a huge gain in A-wtd S/N ratio from 88.9dB to 108.4dB (the Melco/iDSD achieved 105psec/94.6dB). Chord’s battery-powered Mojo [HFN Jan ’16] witnessed a big improvement over its PC/USB performance (50psec/103.8dB) to 11psec/114.9dB with the Stream Box S2 Ultra in the driving seat [black spectrum, Graph 2]. The Melco/Mojo pairing [blue] offered a fractionally lower 5psec jitter but the overall A-wtd S/N was also 1.5dB poorer at 113.5dB. All things considered, the S2 Ultra proves its case as a very able digital signal conditioner. PM

Digital inputs: Ethernet, 2x USB-A, micro USB-B, BT
Digital outputs: 1x USB 2.0 Type A; 1x HDMI
Digital jitter (Oppo Sonica): 112psec (155psec via PC USB)
Digital jitter (IFi Audio iDSD): 11psec (140psec via PC USB)
Digital jitter (Chord Mojo): 12psec (85psec via PC USB)
Power consumption: 8W
Dimensions (WHD) / Weight: 103x37x115mm / 375g
Price: £599

Pro-Ject Audio Systems
Supplied by: Henley Audio Ltd, UK
01235 511166