Streamers — Pro-Ject Stream Box S2 Ultra

The Stream Box S2 Ultra is a compact network bridge from Pro-Ject Audio Systems, built to move files and streams from a home network into an external USB DAC. It contains no converter of its own - its output is digital only - so the box works as a front end for a DAC the owner already has or plans to buy. Pro-Ject builds it in Europe and prices it at EUR 699 in Europe, while the North American price is USD 849.

Key specs that matter

The file system handles PCM up to 32 bit and 352.8 kHz as well as DSD256. Network access comes through Ethernet or WiFi to the 802.11 b/g/n/d/e/h/i standards, and Bluetooth covers Classic plus EDR in versions 2.1, 3.0 and 4.0 together with Low Energy. Two USB-A sockets accept storage, a micro USB-B socket takes a computer feed, and the signal leaves through a single audio-optimised USB-A port. An HDMI socket carries video only. TIDAL, Spotify, Qobuz and HRA Streaming are built in, TuneIn provides radio, and the protocols supported are RAAT, Shairport and DLNA. The box is Roon Ready certified and certified for Audirvana. The case measures 105 x 37 x 105 mm and weighs 375 g without its outboard 18 V, 1 A DC adapter.

Engineering and use context

The audio USB output, as the maker describes it, uses its own internal power supply and parts it calls audiophile grade, which separates that port from the general computing circuitry. The micro USB input enables a PC Detox mode - a computer plugs into the box, the DAC hangs off the audio port, and the Stream Box sits between them to clean up the noisy computer signal. Hardware is based on a Raspberry Pi computer running open-source software. Control runs through the Pro-Ject Play app on iOS or Android, a web browser, or Roon, and a monitor connected via HDMI shows the graphic interface for direct operation without a phone. An external USB drive attached to the box enables CD ripping, and the same drives serve a local library. Up to six units can be grouped for multi-room playback, and Roon streams arrive bit-perfect.

Pairing

Any DAC with a USB input can take the output, which lets an older converter without network connectivity join modern streaming services. Pro-Ject sells the Stream Box S2 Ultra as a bundle with its Pre Box S2 Digital, a DAC and preamplifier in the same footprint, and the two share the S2 case size for stacking. Because the unit has no analogue output, a DAC is always required between it and the amplifier.

Alternatives

The Pro-Ject Stream Box S2 is the non-Ultra network streamer in the same S2 case series.