Mod your Beresford 7520

[leo]

Right, with the original op-amp fitted, I get almost the same shape waveform as with the 4920 but with some extra distortion at full volume, so this is the worst so far. Interestingly I get an almost perfectly smooth waveform from the fixed output, so It seems to be the variable output that is distorting the signal.

I'll do more testing tomorrow night. Let me know if you think of other things for me to try. Oh and I'll try and take some photos of the scope display to make it easier to see what I'm going on about.

If the fixed output is ok but the variable output is clipping at any setting on the pot then the actual op-amp gain may need reducing, should just need a few resistors changing