****ing ground loops

[emorphien]

So something happened yesterday, when everything got disconnected & reconnected we acquired a ground loop hum. It wasn't the new HDTV, that much was easy to make sure of. Couldn't figure it out yesterday but after I got back from swapping our SD cable box for an HD cable box, it was still there.

After going through the rigmarole of disconnecting & reconnecting things I figured out that even if the receiver wasn't plugged in to AC, it was still happening. It was coming in through the cable TV line. If I unplugged the cable line from the cable box or the RCA digital audio line connecting the cable box to the receiver, the 60Hz hum disappeared.

Even if the only thing plugged in to the AC was the subwoofer, it still happens when the RCA digital connects box to receiver and the subwoofer connection is hooked up.

Time Warner is coming tomorrow, although I don't really expect them to fix anything, I'm not looking forward to buying an expensive Cable TV ground isolator as suggested in the Audioholics article (http://www.audioholics.com/tweaks/connecting-your-system/ground-loops-eliminating-system-hum-and-buzz)

I'd switch to an optical cable, but my receiver is out of inputs.

 

[markw]

What sometimes helps for cable induced hum...

..are home-brew cable isolators.

Get two barrel-style 300 ohm to 75 ohm balun transformers, like they used to use on the back of TV's when they only had 300 ohm RF inputs and you wanted to connect an RF cable box, or what they still use on yagi rooftop antennas to facilitate 75 ohm feed lines.

Connect the two twin-leads together so you have the two male cable ends to work with.

If you get lucky, when you insert this between the cable input and the cable box, it will break the ground circuit.

If not, it was a valiant effort and didn't break the bank. And, yes, this has been known to work.

I know the article recommends against it, but it's worth a try, doesn't cost a fortune and, who knows, it just might work for you.

 

[MDS]

Make sure TW checks or replaces the ground block outside the house where the cable enters to ensure a good ground.

If that doesn't help, then worry about a cable isolator.

 

[emorphien]

Make sure TW checks or replaces the ground block outside the house where the cable enters to ensure a good ground.

If that doesn't help, then worry about a cable isolator.

Thanks, I will make sure they do that. Hopefully it helps.

It looks like the cheapest solution (If I have to buy something) is an optical to RCA digital converter box which I've seen for less than $20 at monoprice and elsewhere. I tested it with an optical connection, and no surprise, the noise didn't get through to the subwoofer.

 

[zumbo]

I used a 3-2 prong reducer on my sub that is connected to my surge protector. The surge protector is connected to the wall with a 3 prong plug. I connected a common ground between my surge protector, and my receiver. This grounds anything that is connected to receiver by a patch cable. Cost a buck or two, and the hum was gone.

 

[zumbo]

Make sure TW checks or replaces the ground block outside the house where the cable enters to ensure a good ground.

If that doesn't help, then worry about a cable isolator.

I read to disconnect this ground, as it is the cause of the hum that the cable isolater gets rid of. I had this hum previous to the hum I described in the previous post, and that got rid of it. Climbed up on the roof where TW would not see the ground was lifted.

 

[emorphien]

My sub doesn't have a 3 prong plug, neither does my receiver or cable box. Whatever is going on, the noise is coming in through the cable line.

 

[MDS]

Have you ever noticed that page 1 of every manual for any a/v component has 'Note to cable installer' about proper grounding?

If lightning strikes nearby your incoming cable connection, your house is toast without that ground.

 

[zumbo]

I took this from Adcom surge protector manual:

Grounding Screw
The grounding screw 1# provides a convenient system
grounding point where one or more of the components is
not equipped with a three prong AC cord. The entire
system can be grounded by simply connecting a wire
between the chassis of any system component and the
ACE-615 grounding screw 1#. (The remaining components
will be grounded to the ACE-615 through the
various audio and video coax connections.)

 

[zumbo]

Have you ever noticed that page 1 of every manual for any a/v component has 'Note to cable installer' about proper grounding?

If lightning strikes nearby your incoming cable connection, your house is toast without that ground.

Might be why my TV died the other night. Up on the roof I go.

Oh well, new LCD 1080p on the way.

 

[emorphien]

Based on that, audio connections are completing the ground between my cable line and sub I suppose.

 

[Davemcc]

I'm not looking forward to buying an expensive Cable TV ground isolator

Try this $8.40 isolator. This is what I used and it worked perfectly.
http://www.partsexpress.com/pe/showdetl.cfm?Partnumber=180-075

 

[markw]

Great find!

Try this $8.40 isolator. This is what I used and it worked perfectly.
http://www.partsexpress.com/pe/showdetl.cfm?Partnumber=180-075

This is a good thing to know. It appears to do what that rube goldberg device I described tries to do.

 

[emorphien]

Try this $8.40 isolator. This is what I used and it worked perfectly.
http://www.partsexpress.com/pe/showdetl.cfm?Partnumber=180-075

I saw that, I may try it. I have however read that it may interfere with digital cable, or HD channels.

 

[markw]

I saw that, I may try it. I have however read that it may interfere with digital cable, or HD channels.

But, considering the alternatives. I'd say it's worth a gamble.

 

[emorphien]

They came, they installed an isolator and they left.

Actually he's outside checking the cable lines. When he got here he wasn't quite sure what I was talking about, he had never seen or heard of it before. I explained the ground issue, let him hear the hum, he called someone and we chatted some more and then he returned from the truck with this beastly isolator. It is about an inch in diameter and 2 or maybe more inches long.

It works, and that's all that matters! I didn't have to pay for it either.

 

[zumbo]

They came, they installed an isolator and they left.

Actually he's outside checking the cable lines. When he got here he wasn't quite sure what I was talking about, he had never seen or heard of it before. I explained the ground issue, let him hear the hum, he called someone and we chatted some more and then he returned from the truck with this beastly isolator. It is about an inch in diameter and 2 or maybe more inches long.

It works, and that's all that matters! I didn't have to pay for it either.

SWEET!

 

[yettitheman]

They came, they installed an isolator and they left.

Actually he's outside checking the cable lines. When he got here he wasn't quite sure what I was talking about, he had never seen or heard of it before. I explained the ground issue, let him hear the hum, he called someone and we chatted some more and then he returned from the truck with this beastly isolator. It is about an inch in diameter and 2 or maybe more inches long.

It works, and that's all that matters! I didn't have to pay for it either.

Sounds like an old FasTrap!
http://www.microwavefilter.com/specialtraps.htm

 

[emorphien]

it's a Viewsonics.

I imagine a bunch of people make these things.

 

[Davemcc]

I saw that, I may try it. I have however read that it may interfere with digital cable, or HD channels.

For the future reference of anybody with ground loop issues, I used that device with my cable HD-PVR with no issues whatsoever.