Raspberry Pi I2S to SPDIF Hat

Discussion in 'Digital: DACs, USB converters, decrapifiers' started by Michael Kelly, Apr 30, 2016.

  1. Martin_W

    Martin_W New

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    So this is the head phone jack that isn't supposed to work?

    If all I need to do is plug it into an amp via rca or spdif. I can try that.

    thanks
     
  2. Grahad2

    Grahad2 Red eyes from too much anime

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    Yeah, RCA -> Amp or SPDIF -> DAC/receiver should work just fine.
     
  3. Martin_W

    Martin_W New

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    merci beaucoup
     
  4. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    Sorry Martin, Grahad2 is right. Not sure how you got an older unit, but yes, the HP was removed after that initial revision. As stated though, if that is what you bought the unit for, then we will happily refund your money. And you can keep the unit.

    Cheers,
    Michael
     
  5. gaspasser

    gaspasser Flatulence Maestro

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    Are you attempting to use the 1/4" AES/EBU jack that is a digital out as an analog headphone jack?
     
  6. trung225

    trung225 Facebook Friend

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    Hi @Michael Kelly ,
    I bought a 502DAC two months ago to build a Raspberry Pi transport. The result is very satisfying, but my audio-nervosa still want to squeeze out an additional 1% from my transport. I am planning to replace both NDK clocks by Crystek CCHD-957, so I want to ask if I can do it simply by remove NDK clocks or I need to remove additional resistors to do it?
     
  7. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    OK, first, officially, I can not approve of this as it voids the warranty. The NDK clocks are very tiny, so I hope you have a steady soldering hand. If you proceed, note that there is a 33 ohm resistor in series with the output of each clock. So I would suggest removing only the clock and driving to the resistor from your external clock. Also, the enable of each clock is driven from the PCM5122 GPIO and these enables need to go to your clocks as well.

    Let us know how it works out and if you feel the difference is noticeable.

    Cheers,
    Michael
     
  8. trung225

    trung225 Facebook Friend

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    Thanks Michael for your help. I always know that I will lose warranty by doing this kind of thing. I want to ask one more things, that could I use 45- and 49-MHz clocks in 502DAC or it only works if I feed the MCLK from 22- and 24-MHz clocks?
     
  9. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    The 502DAC uses the same PCM5122 driver as the Hifberry DACPLUS. As such, it expects the clocks to be 22.5792Mhz and 24.576Mhz. I am sure it could be modified for the higher clock, but that would mean hacking the driver.

    Cheers,
    Michael
     
  10. philipmorgan

    philipmorgan Member of the month

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    There's MOTs and then there's f'ing rock star MOTs whose level of transparency and desire to work with customers is truly outstanding. Just wanna recognize @Michael Kelly as the latter kind. :)
     
  11. Martin_W

    Martin_W New

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    oops. :oops: is that what it is?

    that's actually good because it means that I probably haven't broken it,

    Michael, I was only attempting to use the headphone out to test that it was working.

    I'll take it to work now and plug it into my dac and check it there

    thanks
    for you help guys.
     
  12. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    Guys,

    I have gone ahead and designed a digital only board, the 502AES. It will use the same driver is the Hifiberry DIGI plus. There is no analog out so it's strictly for connecting to your downstream DACs. The output it supports is COAX, XLR balanced, and I2S over HDMI. The pinout for that should match the PS audio and the Gustard products.

    Although it will be simpler with fewer parts we will likely keep the price at $79 USD. Mostly as it will be lower volume and somewhat compete with the 502DAC, Still, if you want XLR balanced and/or direct I2S, there is nothing else our there! And you guys really helped teach us more about the marketplace. Thanks! And there will be a case!

    Some screen caps are shown below.

    Cheers,
    Michael

    [​IMG]

    [​IMG]
    [​IMG]
     
  13. philipmorgan

    philipmorgan Member of the month

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    @Michael Kelly Nice! Would a clock multiplier LED make sense as a way to be even more explicit about clock rate without chewing up too much more board real estate or adding too much to the part count?
     
  14. trung225

    trung225 Facebook Friend

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    @Michael Kelly : I'm very happy to hearing about your new 502AES.

    I have some things to suggest. Firstly, could you consider using Flip-flop for reclocking. As I see in the 502DAC, you use WM8804 for reclocking and convert i2s to SPDIF/AES. But WM8804 has intrinsic jitter around 50ps, so I think you could do a more elegant way, by converting i2s to SPDIF/AES via WM8804 and after that reclocks these signal with flip-flop like 74AUP1G79.

    Secondly, could you implement a MCLK input for 502AES, so that some insane people like me can satisfy our audio-nervosa by adding some shiny toys like MCLK from Crystek and OCXO.
     
  15. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    There is no hardware indication of what the clock multiplier he is. That is buried in the driver. I could certainly add some LEDs to GPIO but then who would write the code, who would upstream it to the various kernels, distributed to the players, etc. That is the main reason I cloned the Hifiberry stuff. No software!

    Cheers,
    Michael
     
  16. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    Those seem like pretty good ideas. I wonder though, does anyone else in the forum feel the jitter coming off of the 502 DAC was a problem? I'm not saying it could not be improved, but I do wonder what level of improvement would actually be gained in real use. Still, it is definitely worth looking at. It does not seem to be that complex. Would you happen to have a pointer to an example circuit?

    Cheers,
    Michael
     
  17. Clemmaster

    Clemmaster Friend

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    Isn't the WM8804 used with the external clocks?
    I believe the 50ps jitter is when the chip's PLL is used, instead.
     
  18. damaged-goods

    damaged-goods Acquaintance

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    I got my 502DAC recently and it works great, very easy to set up! It sounds better than the Hifiberry Digi+ I've used previously and so far I've just pwered it through the pi (but with a sbooster supply). Thanks for this nice piece of gear, love it!

    @Michael Kelly, is there still a plan to make this acrylic box for the 502DAC? I'd love to get one.
    Also, can the 502AES be used with a BNC to RCA adapter?
     
  19. trung225

    trung225 Facebook Friend

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    Yes, but we don't know how much jitter will be when WM8804 uses with the external clocks too. I don't know about Pi2design's measurement devices, but I think it could be beneficial if we use simpler parts to do the reclock things. In my experiences, small and simple parts normally have better jitter performance (WM8804 vs FPGA for example). And D-type flip-flop chip is not exactly too expensive to implement.

    @Michael Kelly :
    I think 502DAC jitter is very good. But from several reports from people who use Ian's FIFO reclocker and my experiences with SGM and Aurender Music server, better clocks like some OCXOs are really beneficial. So I think it will be great if you implement external MCLK input. Normal customer will use the stock clocks. Someone likes me can use external clocks. Best for both worlds. :D
     
  20. steklo

    steklo New

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    Hi Michael,
    I'd also encourage you to offer some kind of ultimate version! I don't know if you have already checked the Allo DigiOne but this seems to have pretty low jitter. There is even one review out there (in french) that compares it to 502DAC and Digi+:
    http://forum-hifi.fr/thread-4520.html
    Best regards
    Stefan
     

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