Raspberry Pi I2S to SPDIF Hat

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

  1. Scott Kramer

    Scott Kramer Friend

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    Ut oh, hope that isn't nervosa setting in :p -- anyway how about piCore 3.10 *non* advanced-audio kernel... does that sound the same as 3.02?
     
  2. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    Yes. The center pin is the signal while outer two pins are ground. This is similar to the way CUI does it, but Switchcraft does the opposite.

    We did not do it since there would be no mechanical stability and I was worried the board would be damaged. But as long as you are willing, give it a go!

    Cheers,
    Michael
     
  3. Poleepkwa

    Poleepkwa Friend

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    I see if I can source some replacements. I would like hear how it sounds as a DAC too.
     
  4. hifiandrun

    hifiandrun Almost "Made"

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    Hi Michael,
    I de-soldered the RCAs for the DAC section upon receiving your testing board and have not tested them yet. Looking at the pictures of your new board, it seems that there is a switch (two pins) for using either BNC or AES(XLR). I only connected BNC for testing. Maybe I need to short or disconnect the equivalent pins on the testing board to eliminate the noise/buzzing?
    The production board looked great, much better quality in fabrication. One question, I saw no holes going through at the places of the 40-pin GPIOs. Does this mean that no stacking of HATs on top of the new board?
     
  5. hifiandrun

    hifiandrun Almost "Made"

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    LOL, I am sure that is one of the major reasons. But I did spend several hours comparing the three versions on last Saturday. There were much subtle differences between the two 3.10 compare to, say, the differences between the I2S Pi DAC/converter and the F-1 XMOS usb/spdif converter. I was hair splitting - most of the time I wanted to convince myself that the newer versions were better - newer software, right? But I ended up going back to the older 3.02 version. I posted here hoping to get opinions from you guys who happened have tried those.
    To my ears, the piCorePlayer 3.10 Audio-optimized version was a little better compared to the 3.10 vanilla version - a little higher resolution. Those two 3.10 versions shared a warm and bold sound signature, but also a little restrained at the same time. The 3.02 version had an open, relaxed, transparent sound signature, and the bass was more palpable. The differences between the 3.02 and either 3.10 versions were larger than the differences between the two 3.10 versions.
     
  6. Scott Kramer

    Scott Kramer Friend

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    Ok, I'll do some AB'ing on 3.10 & 3.02 -- did you have any non-default settings, such as CPU, HDMI disable, squeezelite...?

    I'll do my usual settings on both: CPU (stock speed, but force turbo) so the CPU is not jumping around clock speeds, and HDMI disable.
     
    Last edited: Jan 24, 2017
  7. hifiandrun

    hifiandrun Almost "Made"

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    I have not tweaked any settings. I put the downloaded images on three microSD cards - same brand, same size/speed. LAN, Jivelite installed, no LMS. LMS was on another SOC, also LAN connected. Separated 5V LPS power for the DAC board and the Pi board. Looking forward to your comparison. I will set to turbo and disable the HDMI. Thanks.
     
  8. Scott Kramer

    Scott Kramer Friend

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    There is one setting thats enabled on 3.10 now, but not 3.02.

    It's squeezelite *use* MMAP -- try turning that off in 3.10 (remove the 1 in the screenshot) before you change anything else.
     

    Attached Files:

  9. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    The jumper affects the output voltage level on the BNC, not the XLR.

    We switched to an SMT header for this hat. The height of the connectors makes it unlikely to stack on top of it, so it will need to be the "top" of any stack. The two goals were, 1) eliminate any "stubs" on the high speed I2S signals, and 2) make it easier for manufacturing as the through hole version required hand soldering of the 40-pins.

    Cheers,
    Michael
     
  10. rvsixer

    rvsixer New

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    Looks like a great device.

    So just to confirm, does it appear as a single sound card to the player software, and output to all outputs concurrently? Or does one actually have to pick a different device when switching to a different output?

    I want to connect to my AVR via SPDIF, and to my headphone amp via RCA (not to listen concurrently of course, but it would make it oh so convenient to use without having to switch device outputs in the player software everytime).

    Thanks!
     
  11. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    That's the beauty of this! It looks to software like the hifiberry DAC pro plus with the dual clocks and the PCM5122 DAC. The Wolfson SPDIF transmitter is slaved to the 5122 and follows whatever mode is set. The various digital outputs are nothing more than electrical variations, while carrying the exact same protocol data.

    In this final version though, we did add a small headphone amplifier. It is controlled over I2C and does need to be enabled in the player software. We are not supporting that right away, but will add support for it later.

    Cheers,
    Michael
     
  12. rvsixer

    rvsixer New

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    NICE! Thanks for the thorough reply.
     
  13. haywood

    haywood Friend

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    Any ETA on these now that you're getting production pcbs Michael? And is there a waiting list or pre-order set up that we can get in on? I should probably start assembling rpi build parts.
     
  14. rvsixer

    rvsixer New

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    Agreed.

    Anyone know of any OTS raspberry cases that would fit (or can be modded to fit)? That AES connector must be around 30mm tall!


    UPDATE:
    What's the total height of pi3 + 503? I found a case that has 2" inside dimension between top and bottom plates (google HDZ concepts extra high stackable case).
     
    Last edited: Jan 26, 2017
  15. hifiandrun

    hifiandrun Almost "Made"

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    Hi Scott,
    Big thanks. I removed the MMAP setting, now the piCorePlayer 3.10 sounded identical to 3.02. (or maybe a little better? this could be a real nervosa, lol). Happy listening!
     
  16. Scott Kramer

    Scott Kramer Friend

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    Verrrrry interesting, I didn't know for sure that was it, but there's been rumblings about MMAP being buggy in the past. If you feel strongly enough about it maybe bring it up in the 3.10 threads on forums.slimdevices or diyaudio. The piCore devs are there, maybe they'll change the default (and other people may notice it too). Was waiting for your result before trying it... so now know exactly what to change. Thanks!
     
  17. Mban

    Mban Facebook Friend

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    Before you read the following, note that the differences stated here are small (and therefore exagerated in this review to nitpick) and as usual, these are only my opinions.......

    My short review of the 502DAC running on top of Raspberry Pi 3 (I use either Volumio or Raspbian). FLAC, MP3 and internet streams all tested. No other USB connected, no network cable connected. WiFi left on to access the Pi via internet. Chain is Rpi3/502DAC into Schiit Yggdrasil into Bottlehead Mainline into Dynamat modded HD650’s. All of my gear gets power from a custom 4000VA balanced transformer/conditioner feeding a Belkin PF60 conditioner:


    Effect of power supply
    Samsung Tablet SMPS (2Amp) vs. ultra-low noise dual-linear regulated supply (LM338 supply feeding modified linear supply #2 - Salas Reflektor-D, then feeding into 502DAC):
    - SMPS has a hazier sound. Linear supply is clearer and more transparent, better leading edges on sounds. SMPS is slightly more closed in. linear has a larger soundstage. Linear has a blacker background. Linear gives a slightly more realistic tone to all sounds/instruments. Linear has better dynamics and imaging. Less ‘digital’, in a sense, and more natural sound when using the linear supply.


    Effect of digital output connection
    Optical vs. Coax vs. AES/EBU
    - Optical is slightly warmer and less transparent. Coax and AES have a slightly sharper leading edge, and sound more defined and neutral. Coax and AES have slightly greater depth and dynamics. Coax and AES are incredibly detailed, yet very smooth. Sounds are ‘correct’, and sound more like real life instruments than I’ve ever heard from my setup (or any other setup for that matter). Coax and AES very close in performance, but AES may have a bit more detail, dynamics and soundstage width. This difference may be a result of processing of the signals within the Yggdrasil, and potentially not differences from the 502DAC itself.


    THE BIG QUESTION
    Yggdrasil USB input vs. 502DAC AES
    - I ran off of battery power from my Acer Windows 10 laptop. Laptop was setup with Foobar2000 using Wasapi output. USB cable from laptop to Yggdrasil is ‘Strait Wire’ brand. For the 502DAC, I used AES output and the linear power. There was no contest between these two sources! 502DAC sounded smoother, more dynamic, blacker background, more realistic, more detailed, more depth and much cleaner. The largest effect, however, was significantly less listening fatigue using the 502DAC rather than USB. There was usually some quality of leading edges, cymbals shimmer and transient sounds on USB that annoys the hell out of me on long listening sessions, and would become fatiguing over time. This was gone with the 502DAC.

    Raspberry PI 3 USB output vs. 502DAC AES
    - Interestingly, the Rpi3 gave a better sound than my laptop when feeding the Yggdrasil via USB. A cleaner, slightly smoother sound. However, this USB source still paled in comparison to the AES from the 502DAC. 502DAC was still better in every way, as described above.




    Still to do: Analog Output Comparison
    I re-soldered the RCA connectors on the board, then glued them down to give them strength so that they can be used. My next post will compare 502DAC analog out vs. Yggdrasil and vs. couple headphone out ports (e.g. laptop and phone).

    Hope you are all doing well,
    Mischa
     
    Last edited: Jan 29, 2017
  18. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    Guys,
    It would seem this project is a bit cursed! I messed up the ground plane split between analog and digital, but did not catch it in the first revision due to the messed up connectors. With the new revision we get some undesirable noise at ~8K and ~15K running at about -85db. It is coming from the digital section of the 502DAC, not the Pi. I can knock it down below -100db with a cap filter at the output, but that reduces the output above 10K by 2-3db. Not good!

    As for the digital section it is still working extremely well. With our new dScope audio analyzer we can see the carrier frequency accuracy is better than 0.2ppm. This is a reflection of the high quality clocks and is also what the previous revision was achieving. The analog noise does not affect the digital section in any way.

    So now I have another 10 boards that are not ready to sell, but can be offered to those who want to try the digital section. Ah, product development, it can really suck!

    Cheers,
    Michael

    P.S. If you want a unit, send me an email with "502DAC tester" as the subject line.
     
  19. darkstar>eyesoftheworld

    darkstar>eyesoftheworld New

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    I tried to send you a PM, but it wouldn't let me. I'm only interested in the digital out. I'd take one off your hands. Let me know what you need from me.

    Thanks,
    Mike
     
  20. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    Like I said, send me an email with the correct subject matter, then include your mailing address and email.

    Cheers,
    Michael
     

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