PicoMite: driving a small speaker

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Joined: 11/02/2018
Location: Australia
Posts: 1892
Posted: 06:44am 25 Mar 2023      

Some experimenting today.

Feeding the raw PWM signal straight in to an LM386 linear audio amp, no filter on either input or output, resulted in what I think is perfectly acceptable sound.

Rather than come up with more stuff for you to buy, this should work with whatever amp you already have. If you have one with a bridge output you will get more volume, useful with a 3.6V battery supply.

Even a class D chip should work as it's PWM frequency will be in the hundreds of kHz. It should see the 44kHz as just another audio signal, unless it has it's own low pass filter on the input.

If you happen to have an LM386 the connections I used are:-
pin 2 - 1k to Gnd
pin 3 - 1k to PWM signal
pin 4 - Gnd
pin 5 - 100uF to speaker
pin 6 - V+ (5V or battery)

Volume control is a 100R pot in series with the speaker.

Pins 1,7,8 - NC
Edited 2023-03-25 17:07 by phil99