Need A4000 Motherboard

[Castellen]

If whoever repaired it did not do a good job, send it back for a re-service.
As with anything, mistakes can happen and intermittent problems are common with electronics.

Explain the situation to them, and they should be happy to repair the audio problem at no additional cost to you.

The analogue audio stage in the A4000 is barely complicated, so it shouldn't be difficult to get it working properly.

[Castellen]

It should have been tested before and after the job as you would with any other electronics repair.
Was it an Amiga specialist who did the job, or did you just ask someone in the know to replace the 22µF capacitors for you and not test it?

If the capacitors have leaked, there could be a problem with corroded PCB tracks which are causing bias imbalances on the op-amp.

Anyone with some basic knowledge of op-amps and analogue electronics should easily be able to repair it.

Schematics are readily available:
http://amiga.serveftp.net/

[Castellen]

Ahh, that explains it then.
Replacing the capacitors is only half the job.  Sometimes you can get away with doing that only, but if there has been damage caused by the capacitors or something else (like in your case) then you need to do a little more work.

Amiga.fr offer a good reliable service, or you can always send the board to me on the other side of the planet for repair :-P

[Castellen]

Maybe the distortion is less noticable with Eagleplayer as maybe it's only using one channel?
Or perhaps the audio from Eagleplayer is at a low enough level so that if the op-amp bias voltage has been offset, the amplifier's output is not noticably clipping?

Anyhow, if you want to replace the board, that's fair enough.
Interested in selling your old one for a reasnoble price?  I could do with a few more spares for swapout repair jobs.