Incidentally, I'm making progress with my iPod-to-OEM HU research. I now believe I've identified the pins that carry the audio signal from the CD changer in the C3 connector. I just found something on Landroversonly where somebody identified the wire colours that carried the signals - although this was from a 2003 disco with an Alpine HU, I matched up the quoted colours with pin numbers from a piccy somebody took for me of the plugs in the back of his P38 Alpine HU, and then compared that to my 'suspicions' of where the audio inputs lie, based on where the extra shielding in the loom is, according to RAVE. They match up perfectly - it seems like the L audio is on C3 pin 13 (+, red) and pin 16 (-, grey) and the R on pins 14 (+, white) and 17 (-, black).
The BAD news is, this arrangement can only mean it's a balanced signal... meaning you couldn't just splice an iPod connection into it raw, without causing buzz and interference. I'm currently delving into a way round that, though, using a centre-tapped autotransformer designed for audio applications as a 'balun' - which will take the iPod output (unbalanced) and convert it into a balanced signal. Not sure if that would kill the 'buzz' though, as autotransformers don't provide isolation. It depends on how much isolation the audio source (iPod) has between it's audio and power grounds. We may find that it works just fine, but buzzes like a good'un as soon as you plug a charger into it... the infamous 'ground loop' effect!
Theory all done, and already have a circuit design in my head - just need to protoype and experiment now (difficult without an Alpine setup in front of me to play with) - but if it all works out like I think it will, I should be able to produce an iPod-input adaptor for around the £20 mark.
I may even be able to work a USB charging port into the mix for about an extra tenner... but I'm getting a little ahead of myself there!!
