Hi - Hope someone can offer some help on this issue...

I have a consistant hum while watching broadcast cable TV with all audio components turned off. Only the TV is on. No digital cable box, just direct analog. The hum is coming from my powered sub. When the picture changes on a broadcast, the hum changes in volume/intensity - stange coorelation in my mind.

First, I must say that all of my gear (including the sub) is plugged into a Monster powerbar 1100 conditioner/surge suppressor. I didn't notice this hum at all until I installed the power strip.

My Tv is a Sony 40XBR800. My sub is Atlantic Tech 162pbm. I have the Outlaw 1050 receiver.

Any thoughts on the problem? Anyone suspect a defect in the power strip?

Thanks in advance!
DJ

The cable is your most likely culprit - it's aproblem that occurs with analog or digital, as its more a function of the wiring than the signal format. If you haven't done so already, check out this recent thread for some info on ground loop trouble in a cable signal. A device such as the Xantech 63400 Ground Breaker (available on this page ) should get you squared away.

While I do agree with Msr. Gonk, I do have to take issue with your inital description.

"I have a consistant hum while watching broadcast cable TV with all audio components turned off."

There is a major contradiction here.

As Gonk suggested, you may have a ground loop problem. Experimenting is in order. Please keep us informed as to your progress.

Paul

If you have a ground loop problem with your cable, it'll manifest itself whether your other equipment is on or not. Another thing to look into is whether or not your cable is grounded to the same grounding stake as you electrical service.

If the power cord to the sub is a three prong type, try getting an adapter like THIS one which should help with the hum.

Thanks for the repsponses...

I should have thought of this as a possible source of the problem sooner, but here goes...

I have a heavy gauge drop cord between the sub power cord and the power strip - could that be causing some interference?

DJ

It's possible, I suppose, but unlikely. Is the power cord on the sub two-pronged or three-pronged? It only hums when you're watching TV? Are you sure?

Try plugging your sub into a separate outlet, not the power strip. If that works, get yourself a surge protector for the sub only.

I have a problem using the adapter as a ground break! The adapter pictured, if installed correctly, is supposed to have the screw holding the plate to the outlet placed through the loop and screwed into the plug. This gives you a ground path to your panel. If you don't install it this way you have interrupted your "saftey wire"!

Hullguy makes an excellent point - these are called "cheater plugs" for a reason. They can be a useful diagnostic tool, but it's not a good permanent solution.

Does the subwoofer stll hum when the cable bringing the audio signal to the subwwofer is removed from the subwoofer?

What if the subwoofer input is shorted?

I have a similar (36") Sony. It's power supply is a switching type power suply (not a linear one) and these type of supplies may be putting high frequency junk on the AC line (and radiating it into the ether as well). Perhaps you sub is sensitive to this junk.

This is unrelated to your problem, but light dimmer switches also put junk on the AC line and can cause a hum (or buzz) to come out of the speakers because one or more pieces of audio equipment is sensitive to it.

Paul

Here is a link to information from the manufacturer of most of my speakers, including subs, which addresses the exact issue with hum. Maybe it will be of some help.