PicoMite: driving a small speaker

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Joined: 24/12/2017
Location: Australia
Posts: 1601
Posted: 01:46am 25 Mar 2023      

  phil99 said  All the above is good as a general discussion about audio but loose sight of Tom's requirements.
1) Compact
2) Adequate quality and volume for a small handheld device.
No HiFi high power output needed.

Thank you for trying to inject some sanity into this post. Going back to Phil's post that he linked to, he also says :'The output filter makes no audible difference, though the scope shows it greatly reduces the 44kHz at the speaker.'

The output filter makes no audible difference

This suggest to me that the speaker and our ears are pretty good at filtering out the PWM frequency. If some of it gets through to the speaker then it is of no consequence. If your cat runs to the other end of the house and bats fall from the sky then you may have to address it, until then...

Since the signal is being fed through an audio amplifier a filter is necessary to recover the audio signal from the PWM. I would stick with a single one stage RC filter for the time being at least until the circuit is performing satisfactorily. Two stages would be better but less compact - a single stage LC filter would give the same result and be just as compact.

From what I've seen on the web, the amplifier seems adequate for the job so I would stick with that.