Feedback

You are probably confusing "feedback" with "ground loop hum" and they are ENTIRELY unrelated. Raise the volume till you hear a little hum, select and disconnect EACH INPUT one at a time until you find the input that causes the hum. When you know which 2 components are having trouble together, you can change where they are plugged in... connect them to the same power outlet. If that does not stop the hum, run a 20 gauge wire from the ground post on the AVR to some bare-metal screw on the other component so you connect the 2 chassis together directly. Your AVR likely does not have a grounded chassis as most of them made today have 2-wire power cords with no connection for ground.