A Digital Audio Recorder For TOSLink

Every now and then in our travels we come upon a project with such an obvious need that it’s almost a surprise nobody has thought of doing it before. So it is with [Elehobica]’s project, an audio recorder for S/PDIF audio streams. It’s the device you could have used, years ago!

S/PDIF, or its optical fiber cousin TOSLINK, is the digital output you’ll find on the back of Hi-Fi equipment, it’s a serial encoding of an uncompressed digital audio data stream dating from the era when CDs were new. Its relative simplicity may be what’s given it longevity — it’s easy to implement so it plugs into pretty much everything.

Perhaps back in the day it might have been a pain for an 8-bit microprocessor to handle, but in 2026 it’s no bother for a Raspberry Pi Pico. The project is a small PCB with the Pico, a few interface components, and an SD card socket, and it sends what it hears on the input to the card as WAV files. We particularly like its smart sample rate and bit depth detection, and the way it cuts up tracks based on periods of silence. If you work with SPD/IF, this is going to be a useful tool.

Perhaps it could even be fed with a laser!