I just received a 520 that I ordered from onecall. When in surround modes on any source, there is a faint buzz that comes from the center speaker. It goes away when switched to stereo mode. I can only hear this when I am right next to the speaker, and it does not increase as the volume on the unit increases. I also demoed a 320 a while back and it did the same thing. Am I just being picky, or is this a problem? The happens on any speaker connected to the center channel. I have tried unplugging everything from the unit and tried plugging it in, in different rooms. Any help would be great.