JBL Sub W/ LOUD hum

[Rkyle]

Hi, for our home theater system we have a jbl sub that started this obnoxiously load hum in the middle of the night while I was sleeping. It sounds like the hum of a transformer but way louder. I've opened the unit up and had a look inside where i found nothing (or at least can't tell) wrong. It is a powered sub and as soon as you plug it in it immediately starts buzzing very loud whether the volume is high of lowest and whether there is any audio sources connected or not. So if anybody has any ideas about why this might be happening, I'm all ears.

 

[americanaudiophile]

Sometimes spontaneous hum is caused by an internal problem in the subwoofer. Not much you can do about it.
The buzz you are getting when it turns on could be a ground loop problem. If the sub has a three prong AC plug try a 3-2 ground lifter.
Sometimes a bad ground on your cable box input can cause constant buzz on all inputs. Try disconnecting the coax input on the cable box (you don't need to be on that input when you disconnect the cable). A RF ground isolator will solve it if that's the issue.
A bad sub cable could also be the problem.