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Pro-Ject Pre Box S2 digital DAC

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

  1. Julf

    Julf Evil brother of Mark V Shaney

    I agree - there does seem to be an input capacitor. Hmm... Puts us back in square one in sorting out the issue :(
  2. JohnW

    JohnW Trade: Lakewest


    I suspect the click is related to change of sample rate (When we need to select different Base master clock frequencies) - not DC offset.

    You should not hear clicks between 48KHz and 96KHz etc.

    We will look into it and see if we can reduce the level of the click - although we dont experience the clicks on our lab units.

    It would require a user installable firmware update.
  3. Julf

    Julf Evil brother of Mark V Shaney

    That was of course my first thought too, but how would that manifest itself with one amp but not with another?
  4. JohnW

    JohnW Trade: Lakewest

    No idea, if it was DC then the "transient change" would still be heard irrespective if the AMP's DC or AC coupled.
  5. gahabana

    gahabana Active Member

    hi JohnW,
    yes that is correct and you are spot-on. 44.1 to 88.2 to 176.4 is fine. same with 48, 96, 192 ... DSD (DOP) is in the 1st buckett (88.2/176.4) - so yes - that is when the pop happens. ... from user standpoint - if pop is less loud then music (when one presses the 'next song' during 1st one) - one could live with that .... but it kinda happens as well when one songs finishes (silently or even with silence) and another one starts.

    Hope you do manage to check that. My FW version that it says on the device is 2.1 - hope this helps ?

    thank you a million !
  6. gahabana

    gahabana Active Member

    Julf - i have only one amp (Bryston)... the difference between 2 setups (given that bryston has effefctively 2 inputs - balanced and rca and with jumpers at the back you decide which is the 'active' input) is that initially i used Benchmark DAC2 as preamp (as it has analog input as well) for output from S2. then i connected S2 directly to the amp and realised clicks are really really loud even when music is playing at fairly low volumes (e.g. -35 or -40dB).
  7. Julf

    Julf Evil brother of Mark V Shaney

    So just to check that i understand you correctly - when you ran the S2 output via the DAC2, you didn't have any pops, but when you run it directly to the amp, you have the pops?
  8. JohnW

    JohnW Trade: Lakewest

    Just for clarification, the click only occurs between tracks with sample rate change?

    So with no sample rate change then no clicks between tracks?
  9. Hayche

    Hayche pfm Member

    Is the gain lower on this than the mdac? I get a very low hum through the mdac into my power amp. Maybe this is a better match for my power amp.
  10. gahabana

    gahabana Active Member

    hi JohnW - yes - pops/clicks are happening ONLY when samplerate changes and then only when it changes from 44/88/176/352 and 48/96/192/384 (and vice versa).
    If master frequency does not change there are no pops/clicks. Tried many times by now.
    When it does change, then it does not click/pop every time but more then half times it does.
  11. JohnW

    JohnW Trade: Lakewest

    I suspect that he clicks are present with the pre-amplifier but you have there level attenuated by -35dB to -40dB, with digital pre mode the clicks are not attenuated.

    It sounds like the root cause as to why the click is so audible in your setup is excessive system gain. -35dB to -40dB is way too much attenuation for normal listening levels.

    Typically we listen anywhere from -30dB to -10dB (really loud).

    We will see if we can mitigate the level of the click, but having so much excess system gain is sonically not great (due to much attenuation and wasted gain).
  12. gahabana

    gahabana Active Member

    hi Hayche,
    no hum whatsoever. neither when S2 goes directly to poweramp nor when it goes 1st into another preamp (at least not in my setup with Bryston amp and with benchmark dac as a pre-amp).
  13. gahabana

    gahabana Active Member

    Julf, when i ran S2 into Benchmmark acting as a preamp, i heard lot less clicks as i was at the sametime testing roon upsampling to 768 and/or DSD so sampling frequency did not change that often.

    Secondly , i've just replugged it back - pops/clicks can be still heard in that setup - S2 runs at 0db (or -3db) but they are lot less loud. I guess the only explanation is - benchmark dac might have DC elimination or capacitors at input or output or both so it makes it less loud.

    When connected to power-amp directly - and even at -30dB i get fairly loud pops. i would normally listen at -15 to -10db (medium loud to farily loud) ... but pops would be loud and i was worried over damaging speakers.
  14. gahabana

    gahabana Active Member

    JohnW, yes i would normally listen in that range (-25 to -10db) which is from 'i guess people talking volume to loud music volume) ... the only reason why i mentioned -30db or -35db (below that is too low to hear music really - at -50dB it is like very quiet music and at -60db you can barely hear it and at -70db ear must be on the speaker) is cause at -15db pops are really loud through speakers. louder then music (which usually is silent in between songs).
    Now i have just tested via Benchmark DAC2 as a pre and S2 playing at -70dB (cant hear music from 3m) ... it popped relatively loud (volume on benchmark used as a pre is almost at max (3pm)) - which is about the same what i get when S2 connect to poweramp directly.

    I think there is no mismatch - Bryston delivers full power at about the same level where benchmark as dac delivers full volume and its about the same where Pro-ject DAC S2 does - about 2V rms according to specs. I realised same volume when going through Benchmark as pre for DAC which means it's all good.

    Maybe it is my unit doing something specifically wrong ... as i mentioned earlier - pop click does not happen every time when master freq. gets changed but on average half of the time or more i can hear it.
  15. JohnW

    JohnW Trade: Lakewest

    We will try to reduce with a firmware update - basically increasing the time before the DAC comes out of Mute after sample rate change.

    We have a whole load of work ATM, so it will take us a week or two as we want to add other features (Balance control, USB volume control option and Fixed level / Digital Pre-Amp mode) etc.
  16. gahabana

    gahabana Active Member

    Hi, I've connected S2 back via Benchmark DAC acting as a pre-amp (volume on Benchmark close to max -about 4pm, and volume on S2 on -20dB) - level volumes are to my ears the same when i connect S2 direct to the amp, but pops/click are wee little easier on the ear when going via Benchmark as a pre (or I am imagining).

    I set with my iphone flat in my hand 3 meters from the speakers and played 4-5 songs and am including recording here (should be visible to everyone though you might need gmail account - am not certain) here is the link:
    If playback does not work from the browser, download the file - it should have . .m4a extension and play more or less in most of players.

    Songs played are (each for about 3-4 to 10 seconds)
    1. Radiohead/Just, 44.1khz
    2. Killing me softly with his song/Robert Flack, 192khz
    3. Feel it (in the air tonight)/Naturaly 7, 44.1khz
    4. Imagine/John Lennon, 96kHz
    5. Avalon/Roxy Music, DSD64, played as DOP/DSD64
    6. Liberian Girl/Michael Jackson, 96kHz
    7. Madonna something, 44.1khz

    ... order played 1-2-3-4-5-6-7 and then back each song for few seconds.
    In most of the changes you can hear click/pop - some of them very loud some just annoying. The worst one is between 3 and 4 about 18seconds in a sample - it is really loud.

    Hope this helps a bit.
  17. gahabana

    gahabana Active Member

    hi JohnW - sorry for cross-posting - i didn't see your response before posting my recording of 'pops'. Very happy you are aware of the issues - and YES - i can confirm i am thrilled with the 'speed' of DAC handling FS changes ... my feeling is if you mute it for few milliseconds just prior to doing the change it might work great and still be very fast. even 10ms is hard for people to spot between the songs. Benchmark was bad at that ... took in some cases over half a second and i complained to them 2 years ago but their engineering said it's all good and something must be wrong on my side and then when they came out with DAC3 apart from chip change biggest improvement was taking FS change down to 6ms :)

    Balance could be cool (maybe i'd try to use it but i have decent listening space so probably no need) ... USB Volume Control could be handy (Roon can leverage that)... though i will order metal/aluminium remote for S2 as soon as it is available) ... anyhow, i am happy with the feature set and sound. if you get rid of the pops and i think you will :) Pro-ject DAC S2 is a keeper for a long time. :)

    Thank you !!!

    PS. One other point - i think firmware at the moment (sans pops) is really working well. Like awesome well. Didnt really listen to a lot of music just testing a lot over last 2 days and not once did something get locked up ... was not the case with benchmark (e.g. if Benchmark was playing at frequency not at 44.1khz and i rebooted the player - it would not lock though it would think its all ok - only solution was to power it off and on OR via remote switch to usb 1.0 mode and then back to 2.0 effectively resetting it).
    so please please - as you ADD features - try not to screw it up :) cause it is really awesome and i think of high quality !!!

    Lastly, as there is no 'driver' for linux ... i did make a patch for kernel (same one as used for Oppo Sonica DAC, just changing the USB ID of the device to the one that S2 has). Roon figured out it can used 'native' DSD and all the way to DSD512. I did discover an issue when switching from PCM to DSD playback (native DSD64 and DSD128 without any Roon resampling/volume changes etc) that song would start as hiss and then over one or two seconds it began to sound well. As I said - this is probably not complete 'tweak' to native USB support in Linux - some DACs need additional commands to be issued when switching from PCM to DSD so that may be the case with S2 but net is - that also sounds great and i tried upsampling to dsd512 which worked flawlessly :) There are no issues at all when using DOP format (DSD64/128/256) - it was locking immediately... really fantastic little product and i would need to have some god-given ears to hear how/why much more expensive DAC sounds better :)

    PPS. If you guys want me to try to help on linux kernel patch for native DSD support - glad to try to help if i can - feel free to PM me. LOVE your product !!!
  18. left channel

    left channel Well-Known Member

    @JohnW I can confirm I'm getting the same pop sounds as @gahabana. Thanks for planning to release a firmware update so quickly.

    I've also discovered an issue with Qobuz. When streaming from the Qobuz app for Windows, the Pre Box S2 Digital does not sense or display the sample rate. (I've experienced no such problem when streaming from Qobuz via UAPP on Android, nor for that matter Tidal via UAPP/Android nor on Windows, nor downloads on either platform.)

    Hope that's helpful. And thanks for designing such an amazingly feature-packed little Box!
  19. JohnW

    JohnW Trade: Lakewest

    Hey???? really really Odd! the sample rate is calculated internally by the DAC, I'm at a lost as to understand how the Qobuz app for Windows can effect this - we will have to look into it.

    Really odd! :confused: :rolleyes: :)

    We are currently really overloaded with work, but looking at the S2 software is on our pending list - the XMOS interface used on the S2 is a development for our MDAC2 project so this early feedback helps debug the software before its release.
  20. JohnW

    JohnW Trade: Lakewest

    Thank you, both Jarek and I are grateful you like our design - its nice to be able to design such affordable and high quality little boxes :)

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