Raspberry Pi I2S to SPDIF Hat

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

  1. pandather

    pandather Acquaintance

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    I'm hearing the whine too, thankfully I have it with my router/modem/switch etc. in my closet. I could barely hear the thing until I turned my ear towards it, and then it became fairly obvious. It isn't close to strong enough to ring pass my wall though, so I have no issues, but could see where there could be some concern.
     
  2. Poleepkwa

    Poleepkwa Friend

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    Guess I am lucky, as mine is absolutely dead silent at all times.
     
  3. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    Well, three is definitely a trend! My best guess is one of the crystals. I was able to hear it, very faint to me. I placed a square of thermal putty on top of the crystals and it seems to go away:

    [​IMG]

    Can you guys try this at home? Not sure what material you might have. As long as it is non-conductive and won't leave a trace it should not matter.

    We will try some type of epoxy on the production boards. It might only be one of the crystals, or even the ferrite bead feeding them.

    Cheers,
    Michael
     
  4. pandather

    pandather Acquaintance

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    Sure thing, I'll try that once I get home. I have thermal pads, clay, and dynamat, so I'll see if any of them completely fix it.
     
  5. Scott Kramer

    Scott Kramer Friend

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    Hi, more info on the noise:

    First booting (piCorePlayer audio build) the noise is minimal, can barely hear it from a few feet away. It's easier to put ear next to it to hear it.

    First playing music it gets louder and stays even when stopped, can be heard across the room (still not toooo loud but it's there). This is how I noticed it because had music playing on repeat (but audio system vol down). At my desk it's very noticeable.

    Stopping music and having the option "close output" set, a higher pitch is there and continuous.

    It is what it is, maybe a case will muffle it. Would be nice to find the weird component instead of epoxying it--
     
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  6. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    The idea is to epoxy the offending part. Clearly it is a mechanical vibration probably due to a minimal solder weld. If it is one of the low jitter clocks we prefer to epoxy it rather than find a replacement as good and as cost effective. If it is something else then we can look at alternate vendors.

    Cheers,
    Michael

    P.S. can you try something there to dampen it?
     
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  7. Scott Kramer

    Scott Kramer Friend

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    Will do... remember I did post a video earlier in this thread of me pressing on a very specific capacitor next to the pcm5122, killing the noise on the P1. I even removed that cap, then put it back. No change, only pressure stopped it on that board (and maybe only my specific board).
     
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  8. Merrick

    Merrick A lidless ear

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    Got my BNC cable and installed Moode Audio on my Pi. This sounds fantastic! The background sounds blacker, I'm hearing more depth and the sound is more holographic. It sounds more vivid and real than the Digi+ (not Pro) I've been using up to this point. Thank you again for sending me the board Michael! I'm also happy to know that when I eventually upgrade my DAC to something with AES, that the board will continue to be usable.

    If there's anything specific you want me to test for, please let me know. As far as any high pitched whine, I can hear it if there's no music playing and I have my ear pressed up to the unit, which I will never do as it sits on my equipment rack on the other side of the room. I can apply some damping material on it later to test.
     
  9. Mban

    Mban Almost "Made"

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    I should add to this thread that I find the same as above. My ear has to be pressed right up to the 502DAC in order to hear the sound. Also, as Scott found, applying pressure to the center of the board reduces the volume/pitch of the sound. To me, the sound on my board is so low in the first place that it's a non-issue in my case, and can't be heard as soon as my head is a foot or more away from the Rpi3/502DAC.

    Michael, would it be alright to use neutral cure 100% silicone? Main concern would be heat buildup under the silicone if there are any parts that get warm/hot during operation (I haven't tested for any heat produced on the 502DAC board).
     
  10. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    That should work and the silicone won;t stick.

    Cheers,
    Michael
     
  11. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    Actually I completely forgot! I'll check on that Friday (out tomorrow). It's likely the same parts were used as the last batch, so maybe changing it to another vendor will help. Thanks!

    Cheers,
    Michael
     
  12. darkstar>eyesoftheworld

    darkstar>eyesoftheworld Rando

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    Mine has been running for a day. Much improvement over my 4 year old yulong u18 USB/spdif converter with a regen in front of it. I'm running a pi 3 running Kodi (downloaded from hifiberry to be able to run DAC + pro)with a teradak 9vua power supply turned down to 5v. The board is feeding a yulong d18 DAC. Everything has more weight, more detail and occupies a larger space. My wife says it's the most profound upgrade I've done. I was expecting it to be and she was doubting. My unit does have the "whine" I can only hear it with my ear 6 inches from the unit. I'm excited to hook a power supply up to the board. Am I looking for 3.3v? Any recommendations would be appreciated.
     
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  13. haywood

    haywood Friend

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    The 502DAC board needs 5v. Ideally you'd supply power for the Pi separately and remove the jumper to further reduce the possibility of electrical noise but Michael's design does a good job of cleaning things up with even the stock smps.

    Did your wife hear the noise? And is that with a case or without?

    Michael: I don't have anything on hand to do the damping trick, can you give an Amazon link or product name for something appropriate?
     
  14. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    O
     
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  15. darkstar>eyesoftheworld

    darkstar>eyesoftheworld Rando

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    So, I should power the pi with smps, and put my teradak on the board? I'm not sure what you mean by remove the jumper. My wife didn't put her head up to it and she haven't heard it. No case, if anyone knows of one for it, let me know.

    Just put the smps on the pi and the teradak on the board. Then saw where it was clearly marked 5v. The sound is much more relaxed. Loving this thing.
     
    Last edited: Feb 23, 2017
  16. Scott Kramer

    Scott Kramer Friend

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    Untitled 2.png

    @Michael Kelly I put some meat* over the area you suggested and no change. Over that suspect cap it gets louder softer changes pitch with pressure. It's minor but using it at your desk (setting down your headphones) it's only very slightly annoying. Maybe there is variation re: loudness. Your call on it being a problem or not--

    *thumb
     
    Last edited: Feb 23, 2017
  17. haywood

    haywood Friend

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    Normally the hat is powered through the Pi's GPIO pins, there's a jumper next to the power input on the hat that you remove so that it only draws power from the input. You can also leave the jumper on and use your lps to power either the Pi or hat and that will power both but I'm not sure what will sound best.

    If your wife didn't hear it and you can only hear it by getting very close without a case then I wouldn't sweat it. I just bought a cheap acrylic case for now so the bottom was protected, the top is open except for an old iPod case to dampen the noise a bit.
     
  18. darkstar>eyesoftheworld

    darkstar>eyesoftheworld Rando

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    i also have a cheap acrylic case with the top removed. I don't see a jumper next to the power input, just a small red cap.

    I removed the black cap. Gotcha
    Now only the green light is on and music won't play.

    I rebooted and all is well.
     
    Last edited: Feb 23, 2017
  19. Scott Kramer

    Scott Kramer Friend

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    Surprising isn't it!
    I'd keep it simple and avoid the SMPS, let your LPS power both*... and you are powering the pi through the gpio which is better.

    *connected to the 502 directly, not the pi
     
    Last edited: Feb 23, 2017
  20. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    You seem very worried that I will ignore this. I don't believe I am, but it takes a little time to figure things out and come up with an economical solution. Don't worry, we will fix this!

    Cheers,
    Michael
     

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