While examining one of my A-110-1s to help answer a forum question I noticed that it was equipped with a TL064 op-amp. A quick look at the schematics revealed that it is part of the waveform generation. I am not an expert but from what I´ve learned, the 064 is usually not the first choice for audio applications. So just for fun I replaced it with a TL084 I had lying around.
A-110-1 with TL084 for IC2