Have a Harmon kardon avr 225 with infinity speakers. Recently, I noticed a buzzing out of my front right speaker at very low volumes. The Buzzing is virtually gone at normal volumes and above. I switched the front speakers and the buzzing stayed in the same location, so I believe it is a problem with the receiver. The buzzing is loudest at the lowest volume and gradually get softer as I increase the volume. Totally gone if I mute or unplug the input. Input is a optical cable.