Raspberry Pi I2S to SPDIF Hat

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

  1. haywood

    haywood Friend

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    That was my worry as well, especially when we're running these outside of an enclosure that might block a lot of this noise.

    With this in mind I hacked some holes into an old iPod box (from back when they were made of very snugly fitting cardboard like the iPhone) for the power and optical cables and "drilled" a few holes into the top for some really shitty ventilation and the high pitched noise is virtually undetectable.

    [​IMG]

    Obviously this isn't a solution for Michael but in a typical consumer electronics scenario the part(s) causing problems might be perfectly acceptable. ¯\_(ツ)_/¯
     
  2. Br444m

    Br444m New

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    Getting very exited about this hat with all the positive experiences posted here. Anyone did a direct comparison with the Hifiberry Digi+ Pro yet?
     
  3. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    The main advantages we have, as I see it:

    Ultra-Low noise LDO (Linear Tech LT3042)
    Isolated Differential AES via 6.35mm jack
    Proper 1.2V Pk-Pk SPDIF Voltage Level via BNC
    Very good (not great) Analog Out (assuming I get it working finally)
    One driver for digital and analog, no need to switch boards or drivers

    Using optical or RCA I would think the results should be very close, but I can't be sure what effect the LDO will have over whatever Hifiberry used.

    Cheers,
    Michael
     
  4. Poleepkwa

    Poleepkwa Friend

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    This was why I used the optical in my comparison with the Digi+. I was assuming they will sound pretty identical.The difference was bigger than I expected and pretty easy to pick up on. Possibly the Digi+ Pro will be closer to the 502 DAC. Coaxial might yield even bigger differences (or not) Do not have 2 similar coax cables, so not going to bother.
    P. S My unit is quiet. No whine or buzz, even with my ear right on the unit. Are the newer prototypes using different parts vendor?
     
    Last edited: Feb 25, 2017
  5. auri

    auri Facebook Friend

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    My personal Pi project is off to a good start. Picked a Hammond 1444-972 case that I'm thinking of finishing by making an L of 1/2" oak ply over the top and front. Or something lower profile to keep it the exact same size as my Bifrost.

    Stuffed the AMB s11 PSU board today. Transformer coming tomorrow and the Pi itself next week. Should turn out pretty nice.

    [​IMG]
     
  6. auri

    auri Facebook Friend

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    Can someone give me a measurement on the 502DAC? Length from far end of board to the base of the plugs where it would mount on a chassis. Thanks.
     
  7. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    Send me an email at [email protected]. I can get you a dxf or step model.

    Cheers,
    Michael
     
  8. haywood

    haywood Friend

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    If you just need ballpark it looks like around 3.5"x2.25" with the connectors themselves extending well past, especially the bnc.

    An interesting aside with the high-pitched noise is it seems reactive to heat, my temporary ghetto box meant to muffle the noise does that, but at some point it seemingly warms up enough that the board gets to a state like others have said: only audible at very close range, even with the top removed. If I disconnect the power and it cools down the noise is there when it starts up again.

    My bnc cable came and initial impression is the difference between coax and the optical out is subtle, some more energy in the high end and the sound is a bit less smeared in comparison (not that it sounded smeared before but you know...). I also ordered an external ssd (super overkill because the Pi only has usb 2 but it needs to be dead silent and not draw a lot of current from the port) to see how a direct connection to the Pi sounds and especially works wrt things like mpd database updates.
     
  9. darkstar>eyesoftheworld

    darkstar>eyesoftheworld New

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    I had a nice long and louder than normal listening session this weekend. This thing is truly incredible. I can finally enjoy loud music with out fatigue. Notes bloom in and out. Soundstage has never been so deep. On recordings that call for it, I don't hear the music coming out of the speakers. It's much easier to pick out each musician. I've ordered this power supply to go with my other teradak.
    http://m.ebay.com/itm/132017059332?_mwBanner=1
     
    Last edited: Feb 28, 2017
  10. auri

    auri Facebook Friend

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    Got it, thanks. I was looking at the pic posted by @Scott Kramer a few pages ago and didn't realize he mounted it to a Zero. Thought it overhung the end of a full size RPi board. Oops. :rolleyes:

    If anyone is looking for a good power supply for one of these, try the International Power IHTAA-16W. They're an open frame linear regulated PS that provides three outputs, a +5V rated at 2A (the 2.5A RPi rating is absolute worst case scenario with all kinds of crap hooked up) and +/-12-15V which would be perfect for a small chipamp, a hard drive(s) or in my case, op-amp based active crossover boards. Hook it up to a fused IEC inlet and you're good to go. Of course I only came across them once I finished building two AMB s11...

    One of those things that looks like a zillion have been made over the years. They're available on ebay from around $30. http://www.ebay.com/sch/i.html?_fro...C0.H0.XIHTAA-16W.TRS0&_nkw=IHTAA-16W&_sacat=0
     
  11. fraggler

    fraggler A Happy & Busy Life

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    Cool find, though the current for the 12/15V line is pretty low for anything other than a very light weight chipamp. Will look for variants that might allow for a little more power for my all in one box.
     
  12. hifiandrun

    hifiandrun Almost "Made"

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    Here is a quick follow up of my testing report on page 36.

    The 502DAC board is a true HiFi board - even if just for the digital output. IMHO, it can compete with any USB-spdif chain setup cost $500 and more based on my previous A/B tests (to Singxer XMOS F-1 with mods) - they are not in the same league. And I found recently that although the 502DAC board has equipped with an ultra-low noise voltage regulator, the board can still do better with better regulated power supply. It is this board and the Schiit Gungnir Multibit led me started to believe that digital play back can compete with good vinyl setups.

    In my previous report, I used a DIY linear power supply which had two independent 5V outputs - one for Pi board and one for Michael's 502DAC board. The problem was that the output current were low - less then 1 amp for the Pi and the LCD. The yellow lightening bolt sign (under-power sign) showed up all the time on the right corner of the display. As a result, the Pi CPU would keep adjusting its running speed. Recently I made another LPS using similar circuit but a larger transformer. The two 5V lines were typical design around LM1085 regulator. I was surprised that although the under-power sign was gone but I felt the sound was a lot worse compare to my old LPS. It was just not sounded right - grainy, narrow sound stage, and blur image, etc. I tweaked things around, finally it got significantly better than the old LPS. I listed what I did and found:

    1. Replaced the regular three-prong inlet socket with a power line EMI Filter module, which reduced the grainy sound.
    2. Added a C-R-C low-pass DC filter circuit between rectifiers and the LM1085 in the 502DAC power supply. This didn't do too much better in sound, maybe just placebo effect.
    3. Upgraded to two-stage regulation 5V output for Michael's 502DAC board, first stage to 7V then second 5V. A DEXA UWB kit was used for the 5V stage.
    4. Switched to high quality wires for cable between LPS to 502DAC board. This affected the sound, significantly.

    The last finding was a surprise to me. At first, with the first three upgrades, the new LPS still sounded a little bit grainy (digital sounding) and lean. I tried many different things, just couldn't figure out why the newer LPS was worse than the older one. Finally I realized that I just randomly cut some wires from a broken desktop computer power supply to make the cable. Once I replaced those wires with high quality wires, the grainy went away and an obvious improvement over the old LPS. Now I understood what people said about the Schiit Gungnir Multibit DAC - hologram and euphoria sounding. The sound stage was wider beyond the speakers and deeper. The mid, bass, and vocal voice became warmer, liquid, and more present. Instrument separation was better. I could crank up the volume and no fatiguing after long listening session, even with some "hot" recording such as "I am shipping up to Boston" from Dropkick Murphys.

    Happy listening !
     
  13. auri

    auri Facebook Friend

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    Yeah you're right, super tiny. I was thinking of something for my horns.

    Does anyone know, am I good at 5.13V? I have some extra zener diodes but don't really want to swap them out if I don't have to.

    My chassis is ready to go other than the obvious. First board I've stuffed in like 9 years and I didn't get any magic smoke, calling that a win. This chassis size (9x7x2, same as Bifrost) is pretty decent for an RPi and a 2A+ linear power supply.

    [​IMG]
     
  14. hifiandrun

    hifiandrun Almost "Made"

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    Looked very nice. I think that rasPi would like 5.13v over 5.00v. I purposely added a small resister between the ground pin of LM1085-5Vfixed and the true ground to get 5.10V. Most usb cables have thin wires in them cause voltage drop.
     
  15. auri

    auri Facebook Friend

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    Heh, yeah you're right, nothing like Googling the answer to something and opening the official documentation for the power supply requirements to find the first sentence: "The Raspberry Pi 3 is powered by a +5.1V micro USB supply."

    https://www.raspberrypi.org/documentation/hardware/raspberrypi/power/README.md

    Nevermind!
     
  16. haywood

    haywood Friend

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    Tight quarters but it looks good, where did you get it and does it come in black? My lps is a bit longer than 9" though so I'd have to pop the lid and see how much free space there is.

    Now that all my parts are here the sound is sublime, it sounded good before but the lps gives it an ease that makes the subwoofer the limiting volume factor (because too thumpy). The usb attached storage likewise seems to sound better than nas -> wifi but that could be just new toy syndrome talking.

    Mac + Linux talk:
    At first the mpd update was super slow which was perplexing because it's an ssd, but taking a look at the mpd.log there were a ton of errors. I'd ended up going with ext4 formatting with a third party driver for it on my mac, and copying the files directly for speed but that 1) creates an file permissions issue since on the Linux side the user isn't right and 2) it left a bunch of ._ files everywhere that the mpd db process couldn't grok. The permissions were easily fixed with chown and chmod, and the ._ files aren't needed so I just deleted them. I haven't looked to see if setting iTunes and Audirvana to use the Pi shared directory as their library (which is slower than nas but I won't be using them much) is what caused that or if it was using Finder to copy the files.
     
  17. auri

    auri Facebook Friend

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    Hammond 1444-972, got it off Mouser. It was a whole $15. No black but there's always spray paint :D

    I can move the PS over quite a bit, but I figured the further it was from the sensitive electronic device the better. Plus, there's room for a battery, SSD, or anything else in the opposite corner.
     
  18. zeed

    zeed MOT: Gaudio

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    @Michael, do you have a rough idea about when this beauty will be available to public?
    Have you already addressed all the little issues or are you still working on that?

    @testers, since I couldn't join the testing-team I need to ask you: do someone already tested extensively the AES/EBU communication?
     
  19. philipmorgan

    philipmorgan Member of the month

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    It worked great for me with an earlier prototype of Michael's board and the Sonic Frontiers SFD-1's AES input.
     
  20. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    Funny you should ask! I just finished the first unit of the latest revision and the noise is gone! Analog out is working to spec (remember, it's a PCM5122, not the worlds best DAC). We are now going to build up another 6 asap. Assuming all is well with those, we will turn on the spigot and build about 40. They will go on sale as soon as that is done, probably another week. List price is $89USD, but all SBAF members get 20% off.

    BTW, the audible squeal also seems to be gone, but I am going to ship a unit to some of the few that heard it to be 100% sure. I don't fully trust my old ears!

    Cheers,
    Michael
     

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