Hello bluray,
As Mark and kcarlile have suggested, such noise is not normal and all the symptoms you describe point to ground-loop hum. Try connecting the AudioByte amp to a different AC receptacle in your room and don't use a surge protector or power conditioner. Disconnect all inputs. The hum should disappear. If re-connecting any AC-powered device to the Audiobyte amp causes the hum to return, try different combinations of reversing the AC plug on the connected device or using a different (or the same) AC source. One combination will work.
If the hum remains, then call the toll-free number.
Regards,
Alan
