Hi Scott,
I have no idea why Richard would consider shorting the unused input to be inadvisable, as long as the connection is applied several minutes or more after power has been removed. The sub would see the short as a zero volt signal being applied to it through a zero ohm source impedance. That is essentially no different than how it would see the output of a solid state power amplifier that might be connected to that input, with that amplifier being in the powered up state while no music is being played.
And if perchance you are running the MC7100 in bridged mono mode, it is conceivable to me that the hum problem might go away if you were to change the connections and the stereo/mono switch on the amp such that you are running in stereo mode while using just one channel.
Hope that helps. Best regards,
-- Al
I have no idea why Richard would consider shorting the unused input to be inadvisable, as long as the connection is applied several minutes or more after power has been removed. The sub would see the short as a zero volt signal being applied to it through a zero ohm source impedance. That is essentially no different than how it would see the output of a solid state power amplifier that might be connected to that input, with that amplifier being in the powered up state while no music is being played.
His suggestion was to run a ground wire from the ground terminal on the sub amp to the amp or preamp. Is this just a matter of taking a piece of unterminated wire and securing it under the ground terminal on the sub amp on one end and any screw on the back panel of the main amp on the other end?Not sure. If the ground terminal on the sub is the same as the negative signal input terminal, or if it is connected directly to that terminal, and if the chassis of the amp or preamp is not connected directly to its circuit ground (for instance, if that connection is made through a resistor or inductor or capacitor in the amp or preamp), doing that would amount to an alteration of the grounding configuration of the amp or preamp, possibly affecting sonics. I don't think it would hurt to give it a try, though, PROVIDED that you are NOT running the MC7100 in bridged mono mode.
And if perchance you are running the MC7100 in bridged mono mode, it is conceivable to me that the hum problem might go away if you were to change the connections and the stereo/mono switch on the amp such that you are running in stereo mode while using just one channel.
Hope that helps. Best regards,
-- Al