Out of boredom I just spent some time learning about the audio system on my car (a '99 Saab 9-3), with an eye towards seeing what I can do in terms of aftermarket kit. MP3s and satellite radio might be nice, or just a newer non-OEM head unit, etc. But Saab seems to have tried really, really hard to make sure I don't touch anything. Viz:
Volume controls which send control voltages through an ADC to talk to the head unit via packets might be a sign of overengineering. So it looks like the only realistic upgrade options I have are to add a separate mp3 player or satellite radio unit via an FM modulator. The stock stereo sounds ok, so that's probably fine anyhow -- I just couldn't believe the level of complexity in all of its interfaces.
- The amplifier uses balanced connections
- The speakers have odd impedances: 1.8, 2.5, 5.5 ohms
- There is no line-in
- The CD-changer audio-in ports are not activated unless a CD changer is present
- Communication between the CD player and the head unit is via a Saab-specific packet-based protocol, "I-BUS"
- The display is a separate system (SID) from the head unit, and they communicate over I-BUS too
- The steering-wheel controls send control voltages to the SID, which instructs the head unit via I-BUS
In other news: This weekend I'm heading back to Belleville to order a suit for the wedding from my father's store, made-to-measure. Yay, new things! Yay, not paying retail!