Home Theater Questions? Ask a Technician for Answers ASAP
If you uplug the RCA cable from the HSU subwoofer, does it still have the hum?
If you leave it connected, and disconnect the M&K subwoofer from the RCA cable, does the HSU sub still hum?
Have you changed out the AC Input to another location to see if it still hums?
How long have you had the sub for and when did the problem occur?