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    Easy as that, eh? Hats off to you, sir. :) ...

    Easy as that, eh? Hats off to you, sir. :)

    Iíll go with a decent 9V PSU for now and iron out the finer audio details then see how much more energy I have for power supply design.

    Thanks...
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    Swapping the power supply for a better one (a...

    Swapping the power supply for a better one (a Korg 9V PSU instead of a random cheapo) eliminates almost all of the noise. Gah.

    If I wanted to make the circuit more resilient to cheapo power...
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    @fdaniels good question! I had tried that a while...

    @fdaniels good question! I had tried that a while back, but not recently. Running the circuit from a 9V does indeed eliminate the noise.

    So... I need to filter the power supply?
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    I came across this post...

    I came across this post that sounds like a very similar problem to mine, and it made me wonder whether my skimpy breadboard cables were not giving me a clear enough ground connection. I swapped all...
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    The JFET buffer is quite common in guitar pedals...

    The JFET buffer is quite common in guitar pedals (this sort of thing), but a TL07x buffer makes sense too (and should be better quality). Iíve swapped the buffers out for TL071s Ė they work fine but...
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    @fdaniels thanks for the pointer on the inductor...

    @fdaniels thanks for the pointer on the inductor position Ė I think I misunderstood your earlier recommendation. This makes much more sense.

    Hereís the full circuit that Iím tinkering with. One of...
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    Quick experiment Ė I donít think this is the...

    Quick experiment Ė I donít think this is the correct approach, but it does eliminate the noise and maybe that would be helpful in diagnosing the problem.

    I grounded the mixer to the Teensy audio...
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    Iíve made some progress! A few steps forward, a...

    Iíve made some progress! A few steps forward, a few steps back.

    I bought some 33uH inductors and added them to the circuit as @fdaniels suggested. They reduced the power supply whine a little....
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    @jonr @fdaniels @MarkT @Blackaddr thanks for the...

    @jonr @fdaniels @MarkT @Blackaddr thanks for the tips! That all makes a lot of sense. Iíll make some tweaks to the circuit and see how I get on.
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    How to reduce power supply noise

    Iíve been working on a Teensy 4.0-based music machine for a while, and Iím getting down to the last niggly noise issues. Iím hoping this is something people have solved before, but I havenít managed...
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    Adding AudioNoInterrupts() around the stop()...

    Adding AudioNoInterrupts() around the stop() calls in my sketch makes no difference Ė the play() calls still sporadically fail (with or without a delay() between the stop() and the play()).

    This...
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    After a lot of experimentation and digging I came...

    After a lot of experimentation and digging I came across this in the Audio library source code:


    // When changing multiple audio object settings that must update at
    // the same time, these...
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    Thanks, Pete. I tried adding the delay (and a...

    Thanks, Pete. I tried adding the delay (and a longer delay just in case) but it had no effect.

    Keep the suggestions coming! In the meantime I’m going to try adding some debug logging to the Audio...
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    I ran the SdCartTest sketch to check whether it...

    I ran the SdCartTest sketch to check whether it was just a case of the SD reads being slow or inconsistent, but the results were (I think) totally fine. I consistently got values close to:


    ...
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    Thanks, Pete. I tried this but it doesnít make a...

    Thanks, Pete. I tried this but it doesnít make a difference. And in fact it looks like the play() function already calls stop() itself:...
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    Diagnosing AudioPlaySdRaw failures

    Iíve wired up a Teensy 4.0 with two Audio boards for the quad output setup with a 32GB SanDisk Ultra SD card and itís working splendidly. This forum (especially...
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