I've got a Harman/Kardon AVR3550 -receiver. It' been a quite nice basic receiver and it's been enought for my needs... ...but I'm a tweaker I started wondering that what op-amp IC's this receiver is using at the pre-amp part on the receiver. I'm interested to see what kind of those are and how those are connected to the circuit board. So, I opened my unit and tried to find out what IC's there are inside. I found several IC's - quite a few video/audio switches - but couldn't find op-amps for the sound. The circuit board on top has the video connectors. The circuit board at the middle has audio connectors and most of those those switch IC's. The circuit board a t the bottom has power transistors etc. But no op-amps. Does anyone has any knowledge where I could find those op-amps? Or what kind of op-amps it has?