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Have your Pi & eat it: Pro-ject’s Stream Box S2 Ultra

  • UPDATE 3rd April: the Pro-Ject Stream Box S2 Ultra is now certified Roon Ready.


    ‘£600 is flipping expensive for a tarted up Raspberry Pi!’

    Not quite the words of the forum poster but in line with the sentiment: that Pro-ject is ripping off customers by charging silly money for a Pi with open source software and a nice case. Fairy dust or what?

    Actually, strip away the invective and we find a reasonable question. Pro-ject are quite open about the Stream Box S2 Ultra (Stream Ultra) being based on the (CM3 industrial version of a) Raspberry Pi running a customised Volumio operating system.

    This Munich High-End 2018 launch video makes the introductions:

    So what justifies the extra cost? Quite a lot it would seem.

    Enter John Westlake – co-designer of the product – onto the said forum with 1200 words politely and cogently explaining the design principles. Jitter and noise are the focus, with close attention paid to clocking, power supplies (no fewer than eight) and radio frequency filtering.

    I’ve lived with the Stream Ultra for a while now. I know from experience that it’s good. Also that it’s price competitive. But what is it?

    Functionality
    Primarily the £599 / €699 / $849 device is a network endpoint. A network endpoint pulling Ethernet (my preference) or Wi-Fi in and serving its output to a DAC over USB. PCM up to 32bit/352.8kHz PCM and DSD256 – enough for most – and it passes MQA signals to a DAC (confirmed with a Mytek Liberty DAC).

    It’s also a USB de-crapifier (love that word). There’s cleansing circuitry at work already, focusing mainly on reducing noise on the USB signal – manufacturers such as Schiit and Wyred 4 Sound offer similar USB pipe cleaners at varying price points. Pro-Ject / Westlake decided to make this function independent of network bridging for those who want it.

    Running on top as an operating system, a bespoke version of the Volumio operating system that sees Tidal playing directly from the Stream Ultra. Qobuz, Spotify (but not Connect…yet) and web radio are also supported. Users of other services like SoundCloud or Mixcloud are directed toward Bluetooth or Airplay. And if streaming is 100% your thing – i.e. you have no rips or downloads – then the Stream Ultra can simplify things. Bye bye server, see ya later NAS.

    UPNP / DLNA and Roon support keep network drives in play. Or stream from a USB drive plumbed into one of the Pro-Ject box’s two USB inputs. And like all Raspberry Pi-based streamers, we can also ditch Volumio for our favourite Linux distro. The choice y/ours. Pro-ject facilitates it but doesn’t support it.

    All up, the Stream Ultra is a very versatile piece of kit.

    The device itself
    It’s tiny too. Just a small 105x105x37mm silver (or black) box. On the front panel, an on/off button (something a Pi lacks) and another for toggling between network streamer and USB decrapifier modes. Three lights indicate the unit’s connectivity state. Here we also find the first of two USB inputs.

    It’s standing room only on the rear: Ethernet, a second USB input, USB output, power socket and a Wi-Fi aerial (supplied). The micro USB socket off to the right is where the Stream Ultra taps incoming USB signals for cleansing. A standard wall-wart is supplied. End users can bring their own external 18V power supply but Pro-ject claims that third-party offerings won’t make much of a difference to sound quality given the care already lavished by Westlake on the unit’s internal power supplies.

    All signals are sent to a DAC via the USB output. You can also power other 5V kit via the USB inputs. The Pre Box S2 Digital, also designed by Westlake, is an obvious candidate (but this pairing remains untested by yours truly). Finally, power users can attach a touch screen via HDMI for hands-on control of the Stream Ultra.

    Operation
    I ran the box headless, defeating the HDMI output to reduce noise (apparently). The Stream Ultra runs lukewarm so can be stowed away. Check Bluetooth reception in this scenario though – I noted regular dropouts (hardly surprising).

    Power up/down takes around 30 seconds – rush at your peril. For primary use as a Roon endpoint, nothing else is needed – simply enable it as an audio zone inside the Roon app and you’re off to the races.

    For Volumio, we must put the Pro-ject Play app (iOS/Android) on smart device or plug the Stream Ultra’s IP address into a web browser. The user interface is well short of Roon but serviceable. Controlling Tidal isn’t bad. Web radio is convenient. The file player sourcing music from a thumb drive or NAS (the latter via UPnP) is okay with a small library.

    Supporting kit
    For listening, main amplification and DAC duties were shouldered by an Ayre EX-8 streaming amplifier (£7,750 with DAC, USB, and network card) playing through Graham LS6 speakers (£2,200) connected by Tellurium Q Black 2 cables (£270).

    The Stream Ultra was compared to the network card inside the EX-8 (£625 of the EX-8’s £7,750) and the Allo USBridge powered by a 5V SBooster power supply (circa €450).

    Beats as it sweeps as it cleans
    First up, the de-crapifier, courtesy of a Windows laptop running Audirvana, its USB output cleansed by the Stream Ultra before hitting the EX-8 DAC.

    Using Janelle Monae’s Dirty Computer (amongst others) somehow seemed appropriate. Compared to feeding the DAC directly the sound was very similar – difficult to distinguish. Only after much switching over did I hone in on a slightly clearer, tighter, and airier sound emerging from the Stream Ultra. The difference re/defines marginal though.

    Repeating the test using the USB feed from my Roon Core – a NUC running ROCK – only confirmed things. A little rougher around the edges without the cleanser in the circuit but really not something to worry about.

    As network streamer
    Back to the main bout, with three alternatives – USBridge with SBooster (£450), Stream Ultra (£599), and EX-8 card (£625) – vying for streaming supremacy. As with the recent Mytek shootout, this was an apples to apples comparison, all three presenting a similar tonal picture.

    Versus Ayre EX-8
    The network card in the EX-8 is no slouch. Able to compete on an equal footing means the Stream Ultra runs in exalted company.

    In fact, it was more extended than the EX-8 at the top, offering up more air and greater detail. Lower down there was greater control, bass lines being easier to follow. The most prominent difference was in dynamics, the EX-8 being the softer of the two. The Stream Ultra revealed itself as more alive, bringing the music and musicians into the room more – the believability quotient rose.

    I’m late, very late, to the Mark Hollis / Talk Talk party. Through the Stream Ultra the mix on Laughing Stock conveyed more meaning, more atmosphere. Things were starker, the dynamics giving full reign to Hollis’ rollercoaster emotions. Very powerful.

    The delta wasn’t huge – readily apparent when going from EX-8 to Stream Ultra, less so the other way. The Stream Ultra clinched a narrow victory though.

    Versus Allo USBridge & SBooster
    Against the USBridge juiced by the SBooster, a similar picture emerged. More extended treble from the Stream Ultra that led us to greater detail exposure than the ALLO/SBooster combo. Bass was better defined, dynamics were stronger.

    On Tina Turner’s Private Dancer – like Turner herself, seemingly ageless – the drums came on with more snap, the cymbals more bite, the bass line more prominent when heard via the Pro-Ject. The beautifully crafted mix was easier to follow, the contribution of individual instruments more obvious.
    Differences here were greater than with the EX-8 network card but not by much.

    Ultimate Ultra
    Want to squeeze out a bit more? Try a thumb drive plumbed into a USB port, played via the Pro-ject app. User friendliness is limited but it trumps all else on sound quality. Differences are akin to those discussed above – control, air, dynamics all improve – the thumb drive just takes things a small step further.

    As a music player, it’s no Roon. For a few current favourite albums copied to a thumb drive it works well enough though. Consider one’s interest piqued – I shall experiment in future reviews where appropriate (the Ayre EX-8 in for review can play files directly too).

    Conclusions
    Pro-Ject have done a good job on the Stream Ultra, as they did with the Pre Box S2 Digital that I enjoyed last year. Indeed the two would probably make a good pairing – they match aesthetically and can run from single power feed (or Pro-ject’s Accu Box S2 that has both 18V and 5V outputs).
    The Stream Ultra can fly in exalted company, fully justifying its position fronting the Ayre EX-8 and Graham LS6 used here – a combination that sneaks into £10k+ territory.

    Which surely makes the Stream Ultra an over-performer. It’s versatile, the added functionality proving very useful at times. And purely as a Roon endpoint, it’s an excellent choice.
    What a belter!


    John Westlake technical explanation here.

    Phil Wright

    Written by Phil Wright

    Phil is a Brit living in deepest Devon. Think: Tolkien's Shire but with killer cream teas. He's been around since digital audio's inception - he even wrote his dissertation on the introduction of the CD - but today's developments in both music and audio gear make him think 'we have never had it so good'. Phil is a Music-First audiophile with wide ranging tastes (Trad Jazz excepted): 5000 albums in his local library with the remainder coming from Tidal.

    Hi-res techno: Berghain 09 by Vatican Shadow

    KIH #64 – Get real!