I use op-amps in electric guitar effects pedals in conjunction with transistors to create overdrive, distortion and other musical effects. My knowledge is limited technically but I learning through practical experience. I have come across an unusual circuit that I Canaletto sense of: the parts that are confusing are 2 diodes in series and 2 transistors in series the weird par to me is that one of the transistors is a NPN and the other is a PNP. I am trying to follow the input which seems to go through the opamp, then the diodes and then the transistors. Of course there are resistors and capacitors in the circuit it I think I understand their functions.