In the home theater space most people would tell you the age of optical audio, known officially as TOSLINK ... intended for a digital-to-analog converter (DAC) from HiFiBerry.

On the hardware side, [Paul] has posted up his adapter board for a cheap, but very professional looking, optical TOSLINK sender. But if you’re feeling ghetto, you can simply use a red LED ...

Ultra low jitter and high fidelity design using new receiver & D/A converter chip. Converts coaxial or toslink digital PCM/ LPCM audio signals to analog L/ R RCA and 3.5mm Jack audio simultaneously.