pwm audio filter

https://learn.adafruit.com/adding-basic-audio-ouput-to-raspberry-pi-zero

https://hackaday.com/2018/07/13/behind-the-pin-how-the-raspberry-pi-gets-its-audio/

Another 70%: https://daniel.haxx.se/blog/2021/03/09/half-of-curls-vulnerabilities-are-c-mistakes/

8 pin buffer chip:

C5622, Nexperia 74HC244D,653 C96123, 1206 47uF cap C17557, 220 ohm, 1/8w, 0805 resistor C17408, 100 ohm, 1/8w, 0805 resistor C1525, 0402 100nF cap C17398, 1.8k, 1/8w, 0805 resistor C45783, 0805 22uF cap 2x8 pin outputs, each with a ground