I think the key here is it is primarily a USB DAC. I just put an Allo DigiOne in my system and it won’t provide USB the S2 prefers.
sounds like just what i need no hassle just works and a great sound.
thank you
Fritzg, why don’t you try wiht regular PI output … i do get how better SPDIF output from Allo is compared to PI regular … or you could try Allo USBBridge … that should improve whatever is not good with default PI USB ports ?
Just saw this review, the reviewer seemed to like it: https://www.headfonia.com/review-pro-ject-audio-pre-box-s2/
Read from the article: “It [the remote control] plays and pauses Roon”. How is it possible? Don’t you need a USB device between it and Roon Core / endpoint (Pi, laptop…?
Play/pause/next/prev works for me, but I have it directly connected to the computer with USB (through an iFi nano iUSB3). Not sure if/how it works in other cases.
When connected via USB, the S2 shows up as (essentially) a USB keyboard, and sends media keys (play/pause/track-forward/etc.), just like the special keys on top of a USB keyboard with those keys, so if there’s anybody listening for those, they will get those keystrokes.
Roon on PC listens for them and responds. RoonBridge does not listen for them on any platform, so it won’t work if the S2 is plugged into a Pi. (It would be nice if RoonBridge on Linux listened for them.)
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Very clear explanation. Thank you Sir
Any idea what the behavior with ROCK would be? I am guessing similar to RoonBridge, but it’s just that - a guess.
Hi Boris, I tested it with ROCK, no controls unfortunately.
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And? Tell us, I’m most interested! 
Curious what you think. I have been eyeing this for a couple of weeks now. Now that Roon is going to do MQA, I am waiting for that roll out to see the results of MQA through Roon.
If Roon does MQA really well (which I expect) then I will be going with the Pro-Ject Pre Box also. I think that this box has a lot to offer for the price.
MD
So far, it has been boring mostly – in a good way, I guess. I was looking forward to an afternoon of tinkering, but no: firmware update to 2.12 (it came with 2.10 installed) went without a hitch, plugging into Cubox gave DSD512 immediately (running Armbian with kernel 4.14.6), NUC6i5 does not break a sweat upsampling to DSD512 (1,4/1,5x speed), Airport Express (last-gen) supplies a flawless WiFi bridge (strangely, my wife is not too fond of cables across the living room floor).
It has been playing all formats absolutely fine so far: no pops, no crackles, no flaws. MQA decoding has been fine as well (tried a bunch of tracks ranging from 44.1/48/88.2/96 to 192).
A bit too early to make a sound assessment (the little bugger was delivered 2 hours ago), but is seems to be a great match with my AKG K550 headphones (rather modest in todays $$$ times, but I love these phones for closed-back listening). I hooked up an Aqvox 5V/1A linear PSU left over from my Pi days that was tucked away in a drawer somewhere – that probably helps.
As said: more to come. 
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Thanks for your first impressions, Rene. Out of personal interest, and knowing you have/had one too: can you already compare to the Chord Mojo?
I bought one about 6 weeks ago and can give my feedback as well. I will try to keep it brief. (Edit: failed on that point 
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Regular old PCM, it sounds good, about like my PeachTree Audio DacITx, maybe a tad better than that. Also similar in character to my iFi Micro first-generation portable DAC with the ESS Sabre chip, slightly less sparkle on top but with maybe a little more precision than that DAC. Feels about equivalent to my Furutech GT40a - very similar in character. Not as much sparkle on top as my W4S DAC2 which was a price point level up; definitely a half-step down from that DAC. But once my ear adjusts the music is enjoyable. If MQA was irrelevant this would be a good second system DAC or a good entry-level to mid DAC. Feels like a $300-$400 DAC, which it is.
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MQA, with some sloppy A/B testing against the non-MQA same release on Tidal, takes the S2 up a level, at least upon first impression. There is an apparent precision that isn’t there with non-MQA (again, it is relative, and the difference is noticeable but not necessarily a sea-change). I am not saying it has the sparkle or beauty of the W4S DAC2, that part did not change by adding MQA, but a different character altogether; feels more precise. It’s a pleasant change of pace, albeit perhaps a little bit of a novelty.
However, I suspect that a good deal of the favorable impression from the A/B change is the tremendous boost in volume that MQA adds. I have to wonder if that was one of the overall “tricks” the MQA engineers used to create a perception of added quality. I do feel there is a legitimate component of a different character of sound; but I also feel that the major aspect of the flash you feel when switching to MQA is the added loudness.
Does that mean I conclude that MQA is a novelty or just another tweak? Well kind of, but not in a bad way, and not different necessarily from going from redbook to high resolution. To me the quality of the mastering and the source material is, as many others have said, far more influential than any different processing can do to an existing recording.
But I would probably need to have an MQA capable DAC otherwise at the level of my W4S DAC2 in order to do a real apples to apples comparison. Perhaps if you took a DAC at that level and added MQA, there would be an additional bump.
Either way, it’s a fun experience to compare. I’d definitely continue to listen to MQA where available - many more obscure titles need to come out before MQA listening is more than a novelty, similar to the limited amount of multi-channel material out there - and when it gets easier to find through Roon.
Think of it like having a love of very fine artisan cheese or wine…there might be a version that you enjoy eating or drinking because it really emphasizes an aspect of that product that you’d not really delved into before. You might otherwise have your favorite cheeses or wines and this one might not be on that list, but you still enjoy it because it adds an intellectual layer that wasn’t there before.
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I use it from Friday, in my headphone zone, connected directly to Lenovo W530 running Roon Core. I am very happy with it. It matches perfectly my headphone amp (Sound Project, battery powered beautiful amp, done by my friend in Poland) and Beyerdynamics Amiron Home headphones. I feed the power to the unit from TPLink PowerBank. It works, I only wonder if having dedicated LPSU will help or power bank battery is better?
Does anyone tested the box with Allo USBridge? Maybe @allo.com has Pre Box S2 as test unit in the lab? If yes it will allow me to move the good old W530 out of my desk 
Has anyone had the chance to compare the Pre Box S2 Digital with the Meridian explorer2; I currently am using the explorer2 connected directly to a Nuc7i7 running rock and love the sound but I would be interested if the S2 would be a relatively cheap up grade.
Hello Michael, I have both but I do not use them like that. The Explorer 2 is on my NUC for my headphone, the S2 is on my main system to play DSD. dp