sub hum when TV is on (1 Viewer)

[Rick Radford]

I just noticed that when I crank up the Samson channel level input control to 0db, I get a noticeable hum from the sub. It's barely noticeable at -10db. I can't hear it when source material is being played.. but when nothing is playing, it's quite evident.
This only occurs when the TV is on. I thought it might have to do with the receiver power cord being routed behind the TV.. but changing this did not affect the hum.
I moved the speaker wire (12g Carol) around in an attempt to see if this was the problem.. but the hum persists... no change.
Any ideas?
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--RR

 

[Bob McElfresh]

There are 2 main sources of humm:
- Two amps with slightly different grounds. The solution is to use a "cheater" plug on the sub that removes the ground from the electrical socket.
- The CATV coax is injecting 60 hz noise into your system. Test by removing your CATV coax and listening if the humm goes away. If this is the problem, follow this link for solutions:
http://www.dplay.com/tutorial/cablehum.html
Good Luck.

 

[Marc H]

In addition to Bob's suggestions, also, try plugging the sub into a wall outlet on a different breaker from the TV to see if that reduces the hum. If that works, then a power bar with RF filter should be used for all your audio gear but not for the TV.
Sounds like you have the sub connected by speakerwires but if not, and you are using a line level input, use a shielded cable in order to avoid rf noise from the TV.
Make sure you don't have the sub plugged into the AC outlet on the back of your receiver, they hum like a bugger like that as most receivers can't supply enough current through the switched outlet.

 

[MarkO]

I had the same trouble with an amp. The amp humed from its transformer whenever the TV was on. It was worse on brighter lit scenes. I tried everything but nothing helped. I did notice that if i put my ear against the tube i could hear the same hum. It would vary in volume up and down.

 

[Rick Radford]

Bob,
>>Two amps with slightly different grounds. The solution is to use a "cheater" plug>Test by removing your CATV coax>try plugging the sub into a wall outlet on a different breaker from the TV