I have all of my electronics running through a panamax 5100 and have been running my subs with a speaker level input. Recently I have been attempting to run a line level to the subs and speaker level to the tweeter and midrange. My theory is that I am wasting current and energy by NOT using a line level as my subs have their own built in amp. Where is the current and energy going that is not needed or used by the amp? My viewpoint is that I am wasting all of this so the problem arises when I plug the line level into the sub I get a nasty hum. I have disconnected the cable tv from the system with no loss of hum so the hum must be coming from the line level connection between the sub and the receiver. This hum was not present when using the speaker level inputs.

My quick fix is to make a common ground with a small stranded wire between the receiver, which does have a common ground screw on the back for just such a purpose, and to the amp on the speaker. I have not had time as of yet to try this fix but will over the next few days.

XenonMan
I have never thought about bypassing the amps and then using the extra channels that way. perhaps if I cannot figure out the ground loop issue this may become a solution.