550 Radio/Amplifier

[550M]

Well, the old girl turned 20 last month, and has decided to turn the radio down! I have sound coming out of the back of the head unit, but not reaching the speakers. I assume therefore that the Amplifier is on the blink. Anyone know where it is? Google has drawn a blank, and the workshop manuals do not refer to one. Any help or pointers on where it is located would be most welcome. It doesn't appear to be in the dash area.

As an aside, I thought I'd run it around Silverstone Circuit at the upcoming Sunday Service track day. Novice session. Wish me luck...

[550M]

No amp? Bugger. That'll be why I can't find one then.

I replaced the old unit to bring it up to Bluetooth and standard a good few years ago. And i'd already tried two new head units, assuming the new one had had it, before trying the outputs. Hmm....

For the extperts, I've got an Alpine unit fitted, and it's coming up with DC Error? Any thoughts?

Thanks for the advice.