I recently bought a Rotel RB-1070 2x130 Power. When the amplifier is on, even there are no interconnects or speaker cables are connected to the amplifier, there is a really quiet noise coming from the amplifier. I can hear it within 1/2 meters if I pay attention and I can hear it clearly when I put my ears on the amplifier. It's some kind of a buzzing noise. Is this normal?