20 pcbs for $31??? Which supplier?
Amp is stable with 10k pot, but with 100k pot turned half way, or without any pot at the input, it oscillates in lower audible spectrum..
Just by any chance, do you have access to a couple of regulated power supplies? Preferrably standard lab power supplies. Your need two to create the split voltage. Try using this to power your amp and see if it makes any improvement.