I recently bought the sony davs500 system, and I think it works fine in my small room, except for one big thing: There is a noticeble buzzing noise comming from all the speakers. This is not problem when I play loud music but when the volume is below 10 I can here the buzz If I listen carefully, especially if I play classic music. I am wondering if anybody else has this complaint or whether my unit is defect. My unit is hardware-upgraded to multiregion but I don't think that replacing a chip could have triggered the problem? Any advice or comments will be greatly appreciated. thank you.