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


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Turbo46

Guru

Joined: 24/12/2017
Location: Australia
Posts: 1598
Posted: 12:06am 18 Mar 2023      

I just tried the CMM2 playing the game and I can hear no clicks. That may be down to my Lo Fi ears though. I am presuming that the sound is done in the same way. Do you hear the clicks on the PicoMite VGA?

Terminate the input of the spare amplifier to 0v via a 10k resistor and connect it's  speaker output terminals together via a 100 ohm resistor. This should reduce the possibility of the spare amplifier becoming unstable, oscillating or motor boating, which could affect the other amplifier and maybe cause clicking. Add a volume control you may be over-driving the amplifier.

Can you connect the output of the filter to a computer speaker (with amplifier) or a pair of high impedance headphones to see if you can hear the clicks. If not, they may be getting into the amplifier via the power supply.

Connect the amplifier to an external power supply, say 3 AA cells, with the 0v connected together and see if you can hear the clicks. If not, you could try filtering the supply in the same way the SD card is done. Double the electrolytic. I would definitely put an electrolytic across the supply close to the amplifier anyway. There may not much you can do about filtering the SD card on the display board but you may be able to filter the supply to the whole display.

A quote from the link I put in the other post:
  Quote  I WILL DEFINITELY NOT RECOMMEND YOU TO BUILD THIS ON A BREADBOARD, THE DISTORTION RATES ARE HORRIBLE !!!

The amplifier does get good reviews, I think it's worth persevering with.

Bill