[C]

I never had this problem before on my sub (Velodyne), but it appeared after
I upgraded my Yamaha receiver.

The hum appears when the receiver is turned off. The sub does actually
turn itself off after awhile (hasn an auto on/off feature). I've checked
all the outlets in the house for proper wiring. The sub itself has a
two-prong cord, so no 2-3 converter trick to be had here.

And, even more weird (and remember, I =never= had this problem before),
when the amp is off and I turn on the lights on the same circuit as the
amp, the hum appears. Turn off the lights and after a few minutes, the sub
will turn itself off.

I have also disconnected the coax coming into the house, thinking that may
have been the culprit. No luck.

Any one got any insight?

Thanks, all.