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Cable TV / Subwoofer HUMMMMMMM

My HT system works fine until I connect the Television cable to my system. I get a terrible sounding ground loop hummmmm. I have unhooked and hooked up each component and isolated the problem to be between the subwoofer and the cable signal. If I disconnect the subwoofer the hummm goes away and I can enjoy the cable TV. If I disconnect the cable I can enjoy my subwoofer. Once the cable is disconnected I enjoy using my sub with my DVD, VCR and CD inputs, its just the cable signal that screws things up.
So WHAT is the problem, it is driving my nuts disconnecting and connecting the cable and subwoofer. PLEASE, all help his appreciated.
My systems is as follows, A/V reciever Yamaha DSP-A1, Sunfire True subwoofer, Monster HD2000 SVHS interconnects, AQ ruby audio connects, Aerial 10T mains.

Thanks
mainprize
10 responses Add your response
jmcgrogan2's avatar
jmcgrogan2
6,346 posts
 
If you have a powered subwoofer, you could try floating the ground. Mondial sells what is called a MAGIC box, which is a ground isolating unit for video systems. The costs is around $100 if I remember correctly. This might be worth a try. Good luck
triodemark
4 posts
 
A much cheaper but effective solution: convert 75 ohm cable (screw in type) to 300 ohm (flat twin lead), then convert 300 Ohm back to 75 ohm, then connect this onto back of TV or VCR. You will lose approx 6db of signal compare to the Mondial Magic (aprox. 1 to 2 db loss.) You can get these parts from Radio Shack. Happy listening!!
phild
603 posts
 
Check out www.jensentransformers.com They make a $50 CATV gadget that stops the ground loop. It plugs into the cable, and it's about the same size as the above adapters. I hear that Radio Shack also sells a similar item for less. It took the hum out of my system, although it did cause some video problems on certain channels (a side effect of my lame cable provider, I'm sure).
perfectimage
406 posts
 
If I understand things right the ground for the cable is to close to your house ground. The noise jumps from one ground to the other. I had this problem and I bought a MIT ground loop cable. Its looks just like a reguar coaxle cable and is used as such. There are no drawbacks and the cable is of such a quality that it acualy gave me a little better picture. It cost just under $100.00 but its worth every penny.
avguygeorge
2,300 posts
 
Nice interconnects!!!
jcbtubes
400 posts
 
Checkout any store that specializes in HT installations. They'll have a "ground breaker" transformer which installs in-line with the cable coax. The local dealer sells them for about $15. If money isn't an issue, the Mondial unit is a little more impressive (albeit for 7 times the price). Goodluck.
briweve
123 posts
 
Thanks for a great post. My cable jack and plug that I hook my sub into is only a foot away. I have been having this Humming problem for about a year, sent the sub back to get worked on and no one could find the problem. So I have been living with the hum. Can't wait to run home and check this out.
kennyt's avatar
kennyt
1,226 posts
 
Something all of you may have missed, and an easier fix than any listed.
The exact same thing happened to me in my HT when I added seperate power amps to a receiver, what the problem was was having a dimmer swich on a lamp (or wall) in the same line. The amount of noise made by a dimmer switch is often not picked up by a receiver, but will be when seperated power amps (as in your sub) are connected. Power conditioners didn't clean it up either. Switching from a lamp with a dimmer to one without immediately stopped this problem completely!

If this is the problem, it's simple to fix-kill the dimmer switch, if not, you may need to advance to some of the other rec's above....

Good luck!
mainprize OP
1 posts
 
Thanks JcbTubes!!! Walked in to the local HT store and asked for a cable TV "ground breaker" and for $15.00 I solved this very annoying problem.
Hope Briweve has similar luck as he sounds like he has been suffering quite a while.
mg123
192 posts
 
The cable ground breaker is the formal low cost solution, but actually I just attached a wire from the ground on my amp to an aligator clip which I connected to the shield of the cable tv cable (the outside screw connector). You might need to "lift" the ground from one or more of your components using a 3 to 2 prong ac plug adapter as well. Grounding your cable is key, though.
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