An Arduino Due forms the heart of the project, controlling a TEA5767 module, an SH1106 128×64 pixel OLED display and a rotary encoder. The sound signal is passed through an LM4811 headphone ...

I needed a rotary encoder — I pulled a cheap one out of one of those “49 boards for Arduino” kits you see around. Not the finest encoder in the land, I’m sure, but it should do the job.