Not everyone has the Teensy audio shield with the I2S 16 bit interface, so I will investigate using standard ADC analog inputs for audio in, built in DAC for audio out, and a dual PWM output as an alternate audio DAC interface.

The input and output passive circuits are found in the Teensy audio design tool GUI as seen in the video:
https://www.pjrc.com/teensy/gui/index...

The sketches used are from the Teensy example sketches in the Arduino IDE for audio passthrough hardware testing.

Dual PWM details and general PWM calculations
http://www.openmusiclabs.com/learning...
https://www.edn.com/design/analog/432...
https://www.edn.com/design/analog/444...
https://www.ti.com/lit/ug/tidu027/tid...

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