PicoMite: can we explain/fix "ticking" when using PLAY SOUND

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Joined: 16/09/2019
Location: United Kingdom
Posts: 3888
Posted: 10:41am 20 Mar 2023      

Hi folks,

I'm still struggling with this, both with ticking and hissing when using PLAY SOUND:


1. It's not the SD card, it sounds the same with and without the LCD/SD module attached.
2. There is more hissing when running from the battery than from the Pico/USB.
3. I can "hear" the heartbeat LED flashing as a hiss.
4. The output from PLAY WAV is acceptable, no ticking and not significant hissing.

I'm looking to remove/reduce the tick and the hiss, I realise the former may be something that if completely fixable will require me to improve the software, but I'm guessing the latter is a matter of scattering capacitors/resistors/ferrite beads like confetti .

And no I haven't done, or understood everything that has been suggested, I'm even more out of my depth with analog than I am with digital electronics.

Here is my current schematic:

The low-pass filter is the original PicoMite one, I've also tried the one in the more recent PicoMite manuals (4.7mH/2.7nF/33nF/68nF) on solderless breadboard and it didn't seem any better .

What I'm planning to try next:

1. Try a soldered version of the improved filter.
2. Put both a 100uF electrolytic and a 0.1uF between power and ground on the main PicoGAME LCD after the battery switch - which I think is what @Turbo46 is saying ?
3. Update my music engine to remove redundant calls to PLAY SOUND when two consecutive "notes" are the same.

Any other specific suggestions are welcome,