Pro-Ject Stream Box S2 Ultra. Network Bridge/Music Streamer! (English Version)

Pro-Ject Stream Box S2 Ultra. Network Bridge/Music Streamer! (English Version)

Paradise Embedded !

Pro-Ject is trying to solve one of the most interesting (and challenging) problems of modern audio: The interfacing between the data infrastructure and the audio player, both at the hardware level and at the software level. We test its idea, which includes a built-in computer and open source and we present our impressions.

Most music lovers know about Pro-Ject Audio Systems products from the field of analog playback, the turntable. And indeed, Pro-Ject has been instrumental in reviving vinyl in recent years. But with the concept known as “Box Design”, Pro-Ject launches a rich range of small electronic devices, such as amplifiers, preamplifiers, headphone amplifiers, phono, DAC, power conditioners and digital sources. The Stream Box S2 Ultra, the object of our test, also belongs to this last category.

Linux It Is!

With tiny dimensions, only 105mm wide/deep and 35mm high, this device has built-in music streaming capabilities from the popular Qobuz, Spotify and Tidal platforms and can be used to stream music from all these services. Shoutcast software and the TuneIn service are supported to listen to internet radio and can also act as a Roon endpoint.

The S2 Ultra can play music from storage media with USB connection, as well as from NAS devices installed on the home network that support UPnP / DLNA. It also supports AirPlay, for playing music over Wi-Fi from an iOS device or from an iTunes library on PC and Mac, and streaming music from mobile devices via Bluetooth or from servers and applications that support UPnP / DLNA.

Stream Box S2 Ultra has another interesting technology, USB Detox. As described by Pro-Ject, Detox removes digital noise from the stream that reaches the device via the USB port when it is connected and plays music from PC or Mac. What you will not find in the Stream Box S2 Ultra, is a built-in DAC. Its only output connector is a USB port, for connection to a USB DAC, through which it can output PCM audio in resolution up to 32-bit / 352.8kHz and DSD to DSD256.

There are two USB ports on the back of the Stream Box S2 Ultra. One for DAC output and one for connecting a USB drive (there is also a USB port for connecting a drive to the front). On the right back there is a Micro-USB port marked Bypass, for the operation of USB Detox. The HDMI port is intended for connecting a monitor to access the settings.

The Stream Box S2 Ultra is a Raspberry Pi computer operates at bootloading rate with an open source. The device provides internet access and is used to select music and control playback. According to the manual, the settings and options environment can be accessed from a browser on Windows, MacOS, iOS or Android. But the easiest way to operate the Stream Box is with the Pro-Ject Play application for iOS or Android. So, once the Stream Box is connected to the network, the next step should be to download the Pro-Ject Play app from the Apple App Store or Google Play. We can also add streaming services to the Stream Box S2 Ultra by selecting “My Music” in the Settings menu of the Pro-Ject Play application.


Some of the advantages of playing music from PC or Mac compared with a specialized music streamer such as the Stream Box S2 Ultra are that users have the option of selecting the music player and taking advantage of the wealth of features included, while often being more functional and more powerful than music players in the form of an electronic device. However, it is worth mentioning that the manufacturers of devices such as the Stream Box, rightly state that these specialized devices are specially designed for music playback and thus have audio advantages over general-purpose computers.

In the case of this device, a look inside makes the things obvious. You can the special CM3 version (for embedded applications) of a Raspberry Pi, but that’s where the … “external help” stops and the work of Pro-Ject begins The device has a very good power supply (eight local stabilizations) as well as a system for general signal management, to and from the device, via wireless receivers, Ethernet and USB ports, with all these functions starting from one module of LT Technologies (LM811) while Pro-Ject has done very good work at the circuit level. According to published information, CM3 is running a “special edition” of the Linux Volumio which is specialized for playing high quality music.

As we heard Sviatoslav Richter’s Fantasia in C Minor – K. 475, the piano revealed better tones through the Stream Box while the presentation of the space via the PC was noticeably flatter, more two-dimensional. Also in Saint-Saens, Intro et Rondo capriccioso, by Maxim Vengerov, the orchestral textures had more information through the Stream Box and less detailed description via the PC. But these differences were not huge and certainly not enough to surpass the functionality and usability of Windows and foobar2000.

Put in the equation and USB Detox function of the Pro-Ject and things get even better. In Fantasia in C Minor, K. 475, the sounds appeared better and the overall feel was less mechanical and harsh. At Saint-Saens, Intro et Rondo capriccioso, USB Detox released the orchestral presentation and sense of space. It was not a huge difference, but it was enough to continue our listening exclusively with the Stream Box.

The Stream Box S2 Ultra by Pro-Ject is a functional, tiny wonder with many applications. If we choose to connect it to a USB DAC such as the Pre Box S2 Digital, which is proposed by Pro-Ject, we will have a sophisticated, small digital source for streaming and locally stored music. We are dealing with a device that offers a new sense of the possibilities of digital playback, both in a variety of applications and features, and in innovations that affect the daily practice of the audiophile. Every modern digital fan will find many reasons to put it on their rack.


Description: Network Bridge / Music Streamer

Connectivity: Ethernet, Bluetooth, Wi-Fi, USB-A (Storage / Streaming, Detox), HDMI (Monitor)

Compatibility with services: Qobuz, Tidal, Spotify, Shoutcast / TuneIn

Sample rates: 32-bit / 352.8kHz (PCM), DSD256 (DSD)

Control Compatibility: Roon Ready, Shairport, UPnP / DLNA.

Remote control: Pro-Ject Play (App, Android, iOS), Web interface.

Other features: USB Detox, Multi-room (6x).

Dimensions: 105x37x105, (mm, πxυxβ).

Weight: 375gr

Price: €799

Reviewer :George Katrakazas._ΥΒ

Info: Orpheus Audio, tel: 210-5221.524,

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