[BTetc]

I took the radio apart looking for line level outputs. No luck, but I did find the following:

Connector B:
Pin 6=Ground (this is why pin 5-6 didn't work...pin 5 is ground also)
Pin 7="REMOCON" Remote volume control.
Pin 16="SW-AMP+B" Here's the remote turn on lead. I haven't verified this but all the circuitry was there so I have no reason to doubt it.

And - if you're looking for a mute input,
Connector A pin 5=mute when grounded. I tried this and it works.

I have a photo but haven't figured out how to post them yet.

Have fun...