Low and distorted audio output on my Amiga 4000

[spirantho]

I believe from memory there's a 7905 regulator for the -5V. Check the voltages and the capacitors (including ceramics) on the voltages around the op-amp, particularly the -5V on the regulator.

[spirantho]

You're right about it being +/- 12V, but I think I did have a problem on this bit of the circuit. I may be misremembering it but I think a ceramic capacitor had gone short which was shorting the legs of the 7905 and messing the entire -12v line up.
It was something like that anyway.
I've seen a number of failed ceramic caps in AGA Amigas.... Check for discoloration, that can be a giveaway.

First, though, check the connections as Castellen said, I'm only going on a vague memory! It may help though.