PicoMite: driving a small speaker


Author Message
Volhout
Guru

Joined: 05/03/2018
Location: Netherlands
Posts: 3696
Posted: 07:15pm 24 Mar 2023      

@Eejit,

It is very friendly of you to help us find a solution for Tom, but not every pi is the same pi.

The Pi4 uses PWM output at 192kHz.
If you want 20Hz...20kHz, the Pi4 has to reject 192kHz (around 10x the highest frequency 20kHz).
That can be done with simple RC filter as shown in above schematics.

The PicoMite runs PWM at 44kHz (2.2x the highest frequency). Using the Pi4 audio filter will not reject much of the 44kHz PWM frequency. You need a better filter.

It does not harm trying, but you will end up with a lot of 44kHz (inaudible that is) and digital amplifiers (class D) will distort heavily, and cats will avoid your picomite....

Volhout