UnWanted Noise--B-z-z-z-z-z-z-z... (1 Viewer)

[Bobbi]

I just recently started dabbling with rudimentary HT. I have TW Cable. I connect the RCA audio cables to the TW red/white jacks on the cable box and to an input on my HK 3370 stereo receiver--Aux/Tape2--I've tried several inputs on the receiver.

The audio is there but it is accompanied by a steady low-end B-z-z-z-z-z-z... on all the inputs.

I called TW service. They came and replaced the set-top box. Same noise. The clueless TW tech says it's feedback. I need a better interconnect cable.

So today I purchased the top-end ($16.00) RCA interconnect cable at RatShack and another supposedly "shielded" cable at a local electronics store.

Same thing. B-z-z-z-z-z-z-z... I also get the same noise if I use the audio outputs on my ancient NEC TV.

Fiddling around with the routing of the cables seems to alter the level of the noise but it is always there to one annoying degree or another. Not only that but when the interconnects are connected to the cable/TV the noise even leaks over to the other components on the system though at a much reduced level. I can still here the B-z-z-z-z-z... though faintly on Aux, which is connected to my computer sound card, also on the CD player.

As soon as I disconnect the TV/cable box I'm back to pristine sound--no B-z-z-z-z-z... Totally clean audio.

So what gives? Do I need still better cables? A shorter run (the current set-up requires 12' cables)? Could it be the TV producing feedback--even with the cables connected to the set-top box?

Any help--recommendations would be greatly appreciated.

 

[Bruce N]

This is commonly referred to as a "ground loop" hum. I'm not good at explaining things but if you search for that term you should find lots of info. There are ways to break the ground on the incoming cable line.

Hope this helps,
Bruce

 

[Bobbi]

Bruce--

Many thanks. You nailed it.

I bought the 75/300 ohm antenna transformers at Radio Shack for $6.00. They were recommended on a web site found in a "ground loop hum" search. The hum is gone.

Now I can return all the fancy interconnect shielded cables I tried before. None of those made one iota of difference.

Apparently this is a very common problem. Amazing that none of the TW Cable techs knew anything about it. It's scary who's out there in "service" trucks these days.

Thanks again.

 

[Craig Rup]

Have you grounded your receiver or amp twice, check. Obviously if you are using a surge suppressor that has a built in ground and if you have grounded your receiver or amp to a cold water pipe, etc. this may explain your problem. If so remove the ground from your receiver, amp. This may resolve your problem.