Has anyone here played with a Bose head unit from a '90-'93 Riviera? These seem to be fairly rare. However I found one yesterday.
The connectors on the back of it are identical to the normal Reatta radio. Main difference is that the two connectors that normally run to the speakers are used instead for low-level audio outputs. Hooking it up to my bench power supply, (yellow, brown/white, and grey wires on +12v, and importantly, *both* black wires on ground) the panel lights all work and the box seems to power up and function ok. Have not tried the cassette portion, nor hooking up a CD player yet.
For some reason, I thought the Bose units used balanced low-level outputs. However looking at the diagram in the the '90 FSM, page 8A-150-2, it seems like the audio outputs are unbalanced. They also use a separate ground drain for a shield around the three wires. So it seems like it would be trivial to connect it up to a normal amplifier with no balun needed.
I didn't bother buying the amps/speakers. The door systems have a long acoustic chamber that protrudes out and would rely on major mods to a Reattas door panels to incorporate. And that simply isn't going to happen in my car. For now, I just want to use it on the bench to test my junque CD players to see if I can get any of them working, and try out a couple of other ideas.