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Pro-Ject Pre Box S2 digital DAC

Discussion in 'audio' started by miero, May 9, 2017.

  1. GromitInWA

    GromitInWA New Member

    I’m on my way back from CES and was able to get enough time to visit Pro-Ject in their suite at the Venetian. I saw the battery box and also a linear PSU with various outputs. I believe that they will both retail for around $200. I’m not sure when they will be available.

    The battery box is called the Accu Box S2 USB and essentially contains a battery with a USB output. You can see it here:

    The Power Box S2, on the other hand, is a linear power supply without a battery but provides USB power as well as 15V and 20V DC power for other Pro-Ject products. It takes a 20V DC input. This is the back of it:

    Essentially their S2 line being positioned as a modular set of “real hi-fi” devices. Here is the range from the little catalogue that they had:
    [​IMG] [​IMG]

    The Pre Box S2 Digital was being shown with a Mac running Roon driving it via the USB port (no external power) and going into another beefier headphone amplifier to drive a pair of Sennheiser headphones that would have been too hard to drive directly from the Pre Box S2 Digital.

    I also spoke to a gentleman at the Hi-Res Audio Pavillion who was there for Onkyo but had the Pre Box S2 Digital himself and was raving about it.
    WAD62, The Moog and left channel like this.
  2. pj.walczak

    pj.walczak Active Member

    First, thanks for this topic. Based on all the input here I made a decision to buy this beautiful box. It was great choice. It is "brain" of my headphone system. It is connected directly via USB to my Lenovo W530 laptop running Windows 10 (1709) with Roon Core. Then it is feeding my dedicated headphone amplifier, and Beyerdynamic Amiron Home headphones. I love the sound of the system. I really enjoy music.
    JonhW - special thanks for you, first for great design, second for being so active and supporting us.

    DAC is really great. First what I did, was to upgrade firmware to 2.12. Piece of cake. With Roon I am using it with WASAPI driver, with newer builds of Windows the box doesn't even require dedicated drivers, is just using USB Audio 2.0 drivers built in now in Windows. I played all PCM formats, DSD and decodes MQA. Again, easy, working out of the box, and sounds great!

    (Most of people probably know this, but if not, great samples of different formats (and great music by the way) you can download from here: http://www.2l.no/hires/index.html?).

    Pre Box S2 digital deserves best conditions. So that is why I have few more question, to make sure I give this little box the best environment it deserves.
    1. External power supply. Now I am using TPLink PowerBank with 5V/2A. Is this good enough or shall I invest in some linear power supply (in Poland, we do have at least two companies producing them at reasonable prices: Nostromo.audio and Tomanek.net.pl. My question, will LPSU improve anything against Powerbank?
    2. I read in your whitepaper that you invest a lot of efforts to be able to handle even "noisy" USB signal. So my question is it reasonable to invest in something like Allo USBridge (message from Allo is that noise from laptop is up to 100mV, and they provide much cleaner signal lower then 27mV). Again, may question is, does it matter with Pre Box. I assume that when I see Green/Blue MQA logo it means, DAC recived bit perfect signal. But I might be wrong.

    I am not looking to waste money, I do not want to believe in any audiophile voodoo, but if there is something that can give Pre Box better environment to work I happy to invest, as it deserves the best!

  3. brab

    brab pfm Member

    to the designer or users: how will this Project compare playing CDs from a transport with my current Mdac outputting to a balanced power amp?
  4. MagnusH

    MagnusH pfm Member

    Bit-perfect does not mean it's perfect. What matters for PSUs is the jitter and other noise that finds it way into the DAC chips and disturb the generation of analogue signal. Bits-are-bits arguments are valid in some cases (I am almost sure they are valid for Ethernet cables for example), but sadly not for USB input.
  5. Julf

    Julf Facts are our friends

    Let's separate jitter and noise - they are very different. Jitter was an issue before modern DACs with buffering and reclocking. Noise might be an issue - but that is easily tested with an USB isolator. Haven't seen any controlled listening tests showing it makes any difference.
  6. pj.walczak

    pj.walczak Active Member

    PSU - no question here. Good power for DAC is necessary, no magic here (we have both digital and analog sections in the DAC). But my question here is if power-bank is enough or LPSU is better. I do not have enough knowledge to know, which is better for DAC. I would assume Powerbank is as good or even better, but sometimes common sense makes no sense.

    Then feeding audio stream from computer to DAC via USB. Jitter - I believe that with asynchronous implementation and USB Audio 2 that is being used in Pre Box, the device deals with it. So for jitter I think with this particular box we should be OK.
    Noise over USB- here I am not sure. Does it matters only if we are using USB also for power? It doesn't matter at all with all the filters we have in Prebox? Or it matters and having dedicated USBridge will make Pre Box better (again assuming that we are still using good separated PSU)?
  7. left channel

    left channel Prominent Member

    @pj.walczak your results with a PSU of any kind will depend on the quality of the power coming out of your electrical outlet, and your results an anti-jitter accessory will depend on the quality of the signal coming out of your PC. Following is some background, and my results.

    John says when connected via USB and using external power we should only use a third-party battery or linear PSU, to avoid noise from earth leakage currents. Before he gave that recommendation, most of us had tried the stock external switching PSU and heard a large improvement over USB power alone. Most also hear at least a small further improvement from using a third-party PSU. Some of those are switching PSUs purchased before John's final recommendation, but at this point I believe it is a good idea to use only battery or linear PSUs.

    The Pre Box S2 Digital includes USB signal filtering, but not reclocking. Reclocking is necessary to eliminate jitter on the signal produced by your PC. Most of us hear at least a small improvement using an anti-jitter accessory. Some anti-jitter accessories also replace the USB power supply, but with the Pre Box all or most here have found using the external power input is better than USB power of any kind.

    My results:
    Power - I hear a clear improvement using the stock external PSU over USB power alone. I hear no further improvement after upgrading the PSU with a cheap linear wall-wart. That may be because the new PSU is cheap, but more likely because I am in a new house with very clean filtered power.
    Jitter - I hear a small improvement in the signal quality using a USB anti-jitter accessory that cost almost as much as the Pre Box itself, but no further improvement when I rely on USB power through that accessory.
    Mark Dirac likes this.
  8. pj.walczak

    pj.walczak Active Member

    Thanks @left channel !
    Regarding Jitter, I am far from being expert, but if i read the spec correctly we have 16-core XMOS USB chip for asynchronous USB data transfer. This should mean, as long as the source machine is not heavily struggling with performance, jitter should be no problem. In the spec we have even that statement: Jitter as low as 100 Femtoseconds! (six times lower then very good DigiOne SPDIF). My understanding was that jitter is no more problem of the past: Toslink, bad implemented SPDIF or old USB Audio 1 Audio synchronous USB (I have one DAC with synchronous USB input, and sounds really bad compared to DigiOne and SPDIF).
    So to summarize: It is worth investing in power supply. However I am still not sure which one is better battery (standard USB power bank) or LPSU?
    Jitter - small improvement with accessory costs almost as much as Pre Box. So if someone already has it, worth using. For me, I doubt I will hear a difference, I am 40 years also old punkrocker, hundreds of really loud gigs, it is miracle I still hear anything ;)
  9. left channel

    left channel Prominent Member

    @pj.walczak glad that was helpful. A couple of clarifications:

    Over on head-fi.org you'll find posts by the man who discovered jitter, Mike Moffatt, stating that USB jitter is still a problem today. (He also says optical is worse than USB, and coax is better than both.) The Pre Box S2 Digital has a low-jitter clock circuit, but in my experience it does not entirely eliminate jitter. More than one of us has reported hearing an improvement when using an anti-jitter accessory.

    The anti-jitter product I mentioned has more features than the Pre Box S2 Digital product needs, and is normally on another of my DACs. I suggest you look at the AudioQuest Jitterbug, which is only 1/8 the price of this DAC. There is also a product which converts USB to coaxial, the Schiit Eitr, for 1/2 the price of the Pre Box. As I said, we hear a larger improvement from an external PSU, but an anti-jitter accessory does add a small additional improvement.

    As to battery vs. linear PSU, I have tried both with the same results and don't really have an opinion. John has made no recommendation either, and as you can see from @GromitInWA's post above, Pro-Ject offers one of each: a battery PSU (Accu Box S2 USB) and a linear PSU (Power Box S2).
  10. pj.walczak

    pj.walczak Active Member

    Thanks for the input. Did anyone tried using Pre Box S2 with Allo USBridge then? Jitter accessory looks like fixing something that is already broken at the source, Allo promise is that the signal they send from the bridge to DAC will be as good as possible from the very beginning. And it costs 183 USD, its size is about the size of PreBox, and eliminates the need of laptop on your desk. Looks like good choice?
  11. Julf

    Julf Facts are our friends

    Eh? Jitter has been a well-known and understood phenomenon since the beginning of digital transmission systems back in the 1920's (and extremely well described by Shannon and others in the 1940's).
  12. left channel

    left channel Prominent Member

    At least one member of this forum is using this DAC with an Allo USBridge, and at last report he was very happy with it: @anthonyb

    Sorry, let's just say Mike Moffatt was the first to stand up and call the music industry's bluff on digital music, and the first to try and fix it for consumers, developing the first outboard DAC in the 1980s. His colorful comments on this industry are quite refreshing.
  13. Julf

    Julf Facts are our friends

    "First outboard DAC in the 1980's"? I don't think so. Denon and BBC had those in the late 60's and early 70's. And what bluff are you talking about?
  14. left channel

    left channel Prominent Member

    First outboard consumer DAC, probably. First DSP-based outboard consumer DAC, definitely.

    We're getting off-topic here. Feel free to PM me.
  15. Julf

    Julf Facts are our friends

    You mentioned "the music industry's bluff on digital music" here, so I think it is appropriate to clarify it here, not in a PM.
  16. left channel

    left channel Prominent Member

    @Julf in other words, that digital music was inherently better just by virtue of being digital.

    Or in Mike's words, why the first CD player he encountered "really did sound like bats with clothespins on their testicles". :-D

    As I said, a bit off-topic. Perhaps we should start a new thread on DAC history.
  17. Julf

    Julf Facts are our friends

    I would love to see pointers to claims that were made and that proved to be false.

    It is funny how the DAC chips from those first CD players are now extremely popular among the NOS DAC crowd, who think they are the best-sounding ones... :)
  18. left channel

    left channel Prominent Member


    Again, #marketing. Also, #sad.
  19. left channel

    left channel Prominent Member

    @JohnW another user (who will probably join us here shortly) has reported this bug, and I hear the same thing:

    1) set the filter to Optimal Transient,
    2) play an MQA track (we understand this will turn off the filters),
    3) play a non-MQA version of the same track and it will sound thinner/weaker than it should,
    4) change the filter setting and it immediately sounds better; toggle it back around to Optimal Transient and the track sounds normal.

    Firmware is 2.12.
    Tested with the Tidal app on macOS (1 user) and Windows 10 (2 users).
    Tested with foobar2000 on Windows 10 (1 user).
    Mihail IOV likes this.
  20. anthonyb

    anthonyb pfm Member

    @left channel @pj.walczak

    I'll have the USBridge this week and a Talema LPS also on the way from China (to power DAC and Usbridge) so will be able to chime in properly then. So far it sounds good, better than the (admittedly old) DAC1 it replaced. Where it wins out is the DSD, MQA, more inputs, remote etc. What those mean in an auditory sense, I don't quite know yet. I've been feeding (noisy) USB from my Roon NUC (to test MQA) or COAX from a pi+hifiberry digi+ and I'm hoping to see an improvement when the USBridge arrives.
    pj.walczak and left channel like this.

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