[cmjones01]

I've just managed to get hold of an original service manual for the Grundig Fine Arts "IR" range of hi-fi separates. It's quite a piece of work, with a huge amount of detail on how everything works.

It explains how the IR communication works, and it's either terribly clever or a horrible bodge depending on how you look at it. The IR is really just normal AES/EBU/SPDIF digital audio, the same as you'd get on the optical digital input or output of a CD player or PC sound card. The odd part comes in how the components discover each other and communicate remote control commands. Though the CS8425 chip which handles the digital audio also has a data channel available for exactly this purpose, the Grundig components don't use it. They amplitude modulate the digital audio stream with a slightly modified Philips RC5 remote control code in order to pass commands from component to component.

There's also some clever trickery done to get the IR beam sent and received from the right one of each of the four available ports on each component, and to pass audio data through any component that's not currently playing.

The service manual hints at the existence of an IR DCC recorder in the range. Now that I have to see.

Given all this information, it's very tempting to try adapting an existing hi-fi component - like a Minidisc recorder, for example - to the IR system, thus achieving the expandability that was never possible when all this was new back in the mid-90s. That's one for the long winter evenings.

Chris