Buzzing sound from Panasonic sc-pt960 surround system???

I just bought a panasonic sc-pt960 5.1 system. there is a constant faint but hearable buzzing sound coming from the main front 3 speakers mostly the center one. I turn the volume to 1 or low and its a constant buzz. It i turn it off or mute the buzz goes away. As I turn the volume up, the buzz is still there but then the DVD sound works fine to just the annoying buzzing sound. While I am testing the front speakers the back wireless speakers are OFF. I live in an apartment complex, have no dimming switches. What do I need to buy or try to help this to go away? Or do i return everything?

anyone have any idea what to try?