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Optical S/PDIF Bridge: Bit-Perfect Music Assistant Streaming to Any Receiver
I'm building a small device that drives an LED over I²S to blast music through an optical fiber into my receiver's S/PDIF input, giving my home theater prepro proper Music Assistant SendSpin support instead of the AirPlay implementation that crashes my amp and adds up to ten seconds of latency. Because S/PDIF is digital and uncompressed, whatever Music Assistant sends arrives bit-for-bit perfect at the prepro's internal DAC rather than going through a cheap external DAC — a FLAC file really does land intact, not just in theory. The proper LED blaster is in the mail; once it arrives I'll solder everything up, put it in a tiny box, connect it to the receiver, and we'll have 100% digital room-synced streaming in the living room. The idea came from a DIY Perks video, and I'll publish a full build with a blog post and files once the final parts land.
Description
What I'm making
A tiny box that takes audio from Music Assistant and feeds it into my home theater preprocessor over an optical S/PDIF connection. The core of it is an LED driven by I²S — the LED blasts the music through an optic fiber into the receiver's SPDIF receiver input. It might look like an "LED-based music trigger," but that's essentially what's happening: the light is carrying the digital bitstream.
The goal is to give my receiver proper Music Assistant SendSpin support, which should be far more stable and reactive than what I have now.
Why not just use AirPlay
My receiver nominally "supports" AirPlay, but in practice it's a shitshow. Latency here at home is atrocious — up to ten seconds — and it recompresses the decoded waveform, which is a dead end for what I want. On top of that, AirPlay on this receiver doesn't even work correctly; it just crashes the amp. So I'm moving to this solution instead.
Why optical / S/PDIF is the right answer
S/PDIF can be optical or electrical, but fundamentally it's digital and uncompressed. Whatever Music Assistant throws at the little red LED gets played in its purest form, using the DAC internal to the home theater preprocessor rather than a $2 DAC from AliExpress. That's not just theory — a FLAC file played this way gets to the prepro's DAC bit-for-bit perfect. That's better than what AirPlay offers, even granting the counterfactual that AirPlay worked properly on my hardware.
Who else this is useful for
Anyone with a receiver, amp, or prepro with an optical input should be able to use the same thing to get full Music Assistant support. It'll also be useful for people with headphone amps that have digital inputs who want lossless streaming to their device. And soundbars — almost all of them support digital input through both HDMI and optical.
Status and next steps
The proper LED blaster is in the mail. When it arrives, I'll solder it all together, put it in a tiny box, and connect it to the receiver. Once the parts for the final build are here I'll drop a whole build write-up with a blog post and files.
Credit where it's due
The idea came from a DIY Perks video on YouTube (https://youtu.be/1H4FuNAByUs) — that's what got me started on this.