Raspberry Pi I2S to SPDIF Hat

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

  1. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    For these boards the I2S bus is driven from the WM8004. This is because the RPi does not put out a master clock and we need a PLL to recover it. This means the inaccurate BCLK from RPi is multiplied to get a master clock. These clock errors create real problems for the downstream digital devices, causing loss of lock at random times.

    Because we are the master, a second board can not be added. There are XLR to RCA adapters that are reasonable priced. A quick search on amazon for "XLR RCA adapter" turned up quite a few choices.
     
  2. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    HAT crime, I like it! Frankly the whole HAT spec was poorly thought out, but that's kind of like most thing in life!

    We will be designing a case that will have a bottom half that is the Pi, then sides for each HAT with a top plate. We need this because if you add our 502SSD to the Pi plus any one of our DAC/AMP/TUBE/SPD boards you get a streaming server with SSD storage, Wifi and more! Sorry, shameless plug!

    Cheers,
    Michael
     
  3. Vastx

    Vastx Almost "Made"

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    Actually having aes\bnc and rca\toslink in the same board would not be a bad idea at all. I guess all aes users would like to have a rca output just in case. If the price difference is not that much north of 50$ I'd prbably prefer a board with aes and bnc too. We all happen to change dac once in a while, ain't it?
    The speed one could be the basic hat board with rca\toslink and the speed two could be a shield board with all the output one might need (rca\toslink\bnc\aes).

    When you wrote "Hat size is the official supported spec from the Raspberry Pi folks" what you mean by that? What is the downside of being out of the supported specs?
     
  4. tboooe

    tboooe Facebook Friend

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    My only concern is sound quality. If not having Toslink or any other output will help with the sound then I am personally in favor of removing it.

    Speaking of cases, I am glad to hear Pi2 Design is developing one. Count me in for that too! Should I just start direct depositing my paychecks now to you???

    IMO, this is one of the best looking cases available for the Pi:

    [​IMG]
     
    Last edited: May 4, 2016
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  5. Wfojas

    Wfojas Friend

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    I would think most people would need AES and BNC, and use an adapter to make the BNC coax. Toslink is the outlier, I would think.
     
  6. philipmorgan

    philipmorgan Member of the month

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    That's exactly the case for me. I've never heard anything good about how Toslink stacks up against BNC or AES, and my Gungnir Multibit doesn't force me to use Toslink. So for my purposes, BNC and AES (miniXLR would be fine) on the same board would be ideal.
     
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  7. tboooe

    tboooe Facebook Friend

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    The question is who is this product targeted at and who will buy it. I agree that Toslink is not needed if audiophiles are the target. On the other hand, there are still a fair amount of "regular" users who use Toslink. I personally do not because of the bandwidth limitations but it is appealing because of the electrical isolation. I actually use fiber between my Router and my audio pc. I intend to do the same thing with my Pi3 + this board acting as a renderer on my network.
     
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  8. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    So right now most of you seem to prefer RCA and XLR, instead of XLR and BNC? But, BNC to RCA is under $1 for an adapter at Amazon. Heck, I'll include it!

    It seems the desire for BNC and RCA together was the odd one? Just to summarize: 503SPD1 has TOSLINK and RCA, while 503SPD2 has XLR (Balanced) and BNC. All have transformer isolation, though we may offer the SPD1 without.

    Are we good? I would like to send these off for fab this week. But I am kind of doing it for you folks, so your opinions are key! :)

    Cheers,
    Michael
     
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  9. philipmorgan

    philipmorgan Member of the month

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    The 503SPD2 is exactly what I'm looking for :)
     
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  10. tboooe

    tboooe Facebook Friend

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    I am down with 503SPD2 true 110 ohm XLR and 75 ohm BNC. As you mentioned the BNC to RCA converter is cheap. I will take two please.
     
  11. IceUul

    IceUul Friend

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    XLR + BNC is ok, if BNC can make to RCA. Most of the dacs, what have TOSLINK also have some other input:XLR, BNC or RCA, which are better choice than toslink.
     
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  12. fraggler

    fraggler A Happy & Busy Life

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    I know I was a proponent of the budget board since my DAC can't take BNC or AES, but as others have said, it is pretty simple to make a BNC to RCA cable or adapter, and all else being equa, I might go for the SPD2 for potential upgrades down the line.
     
  13. Wfojas

    Wfojas Friend

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    Yeah, and people are not that High End (or far away) to care about the impedance mismatches, or use a terminated t connector if needed for the BNC to RCA. I'm in, too. Like the new case, too.


     
  14. error

    error Friend

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    SPD2
     
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  15. Merrick

    Merrick A lidless ear

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    Sounds like BNC->RCA coax is the best option for me as well.
     
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  16. Vastx

    Vastx Almost "Made"

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    The speed one is done and good to go.

    Do we need a poll for the speed two outputs? Or we can agree on something?
    Personally I wouldn't throw away toslink for wider appeal reason as @tboooe said. I can agree on letting rca go given the possibility bnc->rca adapter inclusion.
    Micheal stated that he's doing this for us, but we've got to think that the more this board sells the wider is gonna be the support through platforms imo.
    And I don't think Mike would be sorry to sell a shitload of these boards.
     
  17. lukeap69

    lukeap69 Pinoy Panther

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    BNC & AES gets my vote.
     
  18. fraggler

    fraggler A Happy & Busy Life

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    I thought the whole point was Speed 1 for the masses, Speed 2 for the advanced crowd. I think it is a differentiation that makes sense and makes it easier to segment the market. The hats are very affordable so switching hats based on need isn't out of reach. I just don't see Toslink as that important to have when the other options are there. Especially on the Speed 2.

    I think these option look perfect, though would say a mini XLR would be more compact and fine for AES if easily available.
     
  19. Vastx

    Vastx Almost "Made"

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    The point stands as you said, still I see no reason to dismiss the toslink. It doesn't hurt the sound quality or the wallet and there is space.
    The speed one is still for the "masses" and the speed two would be for a wider "advanced crowd".
    Don't get me wrong... I never use toslink and I'd be perfectly fine with the speed one.
    And if you guys are happy with the speed two without the toslink I'm happy too :)
     
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  20. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    No I would not!
     
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