My father in law is an electrician... and it just dawned on me what may be causing SOME of the issues
my sub is at the back of the room.
amp at the front
to get the signal to the sub, I run an RCA from the amp to an RCA wall plate. The cable that runs up the wall, along the roof, and down the back wall, is actually speaker cable, and not RCA cable. Then I run another RCA cable from the wall plate at the back of the room to the sub.
Could it be that my speaker cable in the roof, which is acting as an RCA cable, is allowing more hum and noise through?
I tried connecting a LONG RCA cable from the amp to the sub directly, and the hum was still there, but only about half as loud. Still too loud though.
Anyways.... for now I have a solution. Please let me know if this is okay:
1. Turn my sub volume knob down until the hum is pretty much inaudible. My sub volume knob is just over a quarter..
2. Turn the sub output on my receiver up to about +5dB.
Tell me, is this a fairly okay solution? There's no real issue running the receiver's sub output so high is there? I mean it's all relative right? The final output volume of the sub seems to be the same as before (volume knob on half, sub output on -3dB on receiver)