This amplifier was tested and I can get audio and everything see to work fine but when the TURNOVER knobs are on DEFEAT position and the volume is all the way down is making Humming Noise but when I put the volume like quarter way the humming go away and if I put the TURNOVER Knobs too any other position the humming noise go away even with the volume knob all the way down so I think this amplifier need some service the power switch knob is broken please see pictures what you see is what you are going to get