You have got to totally substitute all interface external to the amplifier in order to determine if this noise is a factor of the internal amplifier or an external cause. You have not completed that mission yet. Temporarily swap EVERY (I repeat....every) wire with the tower amplifier that has no noise. You should only need to connect a single channel for this test to provide a conclusion. If you have noise where the tower amplifier did not then the issue is likely an internal one. If there's no noise then the cause is still external and you have overlooked something.
You stated that you received an amplifier with an existing problem (terminal). Have you contacted the dealer that sold you the amplifier?