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Old 07-10-2012, 09:50 PM   #16
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Improper Grounding causing Sub woofer noise


This problem is all to common in the Audio/Video industry.


You're most likely dealing with a ground loop.

Sub is plugged into an outlet that's on a different phase than the outlet the AVR is plugged into is the typical issue.


Troubleshoot by running a drop cord for the sub from the same outlet the AVR is plugged into.


If you then get no hum, you need a ground loop isolator.


Jensen IS the way to go: http://www.jensen-transformers.com/index.html

Pricey but they work...

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Old 07-10-2012, 10:06 PM   #17
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Improper Grounding causing Sub woofer noise


ktkelly, no what they are dealing with is improper grounding of the CATV & Telco to most likely a piece of PVC connected to the meter pan, not metal conduit. Everyone like you likes to throw the term "ground loop" when talking about A/V equipment without knowing what is actually causing the problem.

It is basically like placing a band-aid over a gushing arterial wound on your leg or arm. Does nothing for the real problem, but in turns causes bigger issues. I am sorry, but there are too many uneducated people playing A/V salespeople, or playing A/V engineers, that do not know that all someone has to do, is fix the real problem, and that is fix the electrical distribution system in the structure they are using the equipment in.
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Old 07-10-2012, 10:10 PM   #18
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Improper Grounding causing Sub woofer noise


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Originally Posted by gregzoll View Post
ktkelly, no what they are dealing with is improper grounding of the CATV & Telco to most likely a piece of PVC connected to the meter pan, not metal conduit.
It's certainly not PVC, but holy crap would that be funny if it were true. It does look like it transitions into some type of flexible plastic at the bottom though, hard to tell with just the picture, but that doesn't change anything on how they bonded the phone and catv...

Last edited by stickboy1375; 07-10-2012 at 10:13 PM.
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Old 07-10-2012, 10:15 PM   #19
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Improper Grounding causing Sub woofer noise


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Originally Posted by HarleyP View Post
Hrm ok so this is the first time I've really looked closely at how everything is setup at the electrical panel, what I assumed was the ground for the electrical panel is actually the ground for the catv.

http://i.imgur.com/6A7GF.jpg

I don't see anything going from the Electrical panel. You can see 1 unused clamp at the top, and then 3 wires further down that are bonded to the 'pipe' that goes up to the meter. The bottom 2 are the old phone ground, and the old cable ground, which are no longer used. The top and clean one, is the new one actually going into the catv box and bonding to the splitter inside. (here's a shot inside the box: http://i.imgur.com/pspah.jpg)
If you feel comfortable, open the cover to the breakers and take a picture, I want to see if any grounding electrode conductors exist. Only do this if you feel comfortable...
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Old 07-10-2012, 11:25 PM   #20
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Improper Grounding causing Sub woofer noise


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Originally Posted by stickboy1375 View Post
If you feel comfortable, open the cover to the breakers and take a picture, I want to see if any grounding electrode conductors exist. Only do this if you feel comfortable...
yup no problem, will work on that tomorrow
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Old 07-11-2012, 01:12 AM   #21
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Improper Grounding causing Sub woofer noise


Here's an old trick. Use a U.P.S to power the audio equipment, and use "braided" over sized grounding cable running to a 10ft. 3/4 inch ground rod that is driven into the earth no closer than a 6ft. minimum distance from either the electrical panel's ground rod...or the home's water pipe...(where it enter's the ground, or runs underground).
I'll eat my hat if you have as much as a blip of a hum after that...
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Old 07-11-2012, 06:36 AM   #22
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Improper Grounding causing Sub woofer noise


Daisy chaining a wire from the chassis of one piece of audio or video equipment to that of another is intended to eliminate ground loop problems.

If driving an additional ground rod should help out, connecting it to the other ground rod(s) should be even better. Use a #6 gauge copper wire for this purpose. It may be helpful to undo and redo the various clamps holding the ground wires (grounding electrode conductors) on water pipes and ground rods, which will clean and improve the connection (bonding).
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Last edited by AllanJ; 07-11-2012 at 06:40 AM.
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Old 07-11-2012, 08:32 AM   #23
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Improper Grounding causing Sub woofer noise


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Originally Posted by gregzoll View Post
ktkelly, no what they are dealing with is improper grounding of the CATV & Telco to most likely a piece of PVC connected to the meter pan, not metal conduit. Everyone like you likes to throw the term "ground loop" when talking about A/V equipment without knowing what is actually causing the problem.

It is basically like placing a band-aid over a gushing arterial wound on your leg or arm. Does nothing for the real problem, but in turns causes bigger issues. I am sorry, but there are too many uneducated people playing A/V salespeople, or playing A/V engineers, that do not know that all someone has to do, is fix the real problem, and that is fix the electrical distribution system in the structure they are using the equipment in.



I'd really love to hear why a grounding problem on the telephone line, would cause a problem with an audio circuit. That's too funny.


I, unlike you, will not resort to a personal attack, but will maintain my position that the problem is exactly as I say.

It IS a ground loop, and there are a couple very easy, and completely legal, fixes that are not "band-aids" as you wish to call them.









To the OP:

The real problem is that when you connect that RCA cable to the sub, you are connecting two different electrical circuits that have a different electrical potential. Ergo, you just created a ground loop. Your line level feed is now carrying voltage.

Free fix? Move the sub. Costly fix? Jensen ground loop isolator.



Check out Jensen. They make great "band-aids"....




Ground loops explained:

http://en.wikipedia.org/wiki/Ground_loop_(electricity)
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Old 07-11-2012, 10:10 AM   #24
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Improper Grounding causing Sub woofer noise


If the cable line and the house ground are at the same potential then there shouldn't be a ground loop. So correct me of I'm wrong here but wouldnt fixing the actual cause of the problem be the smarter choice? He's basically isolating the ground in the cable with that ground loop isolator and losing some of his signal quality at the same time.
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Old 07-11-2012, 10:16 AM   #25
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Improper Grounding causing Sub woofer noise


ktkelly, do we even want to get into how non-grounded telco and catv lines can cause issues with the electrical system. Especially in that they both can be used as data.

With the catv, due to it is basically poorly or not grounded at all, and the audio system is also seeing it as a floating ground, and I bet you that to begin with, the home's electrical system is whacked also, is why the OP is having issues.

And also ground loop isolators are band-aids. And if you what to believe in the far reaches of your mind that you are personally being attacked, keep thinking that. I am just pointing out that like you and those on a certain a/v forum do not understand properly fixing the problem, not taking shortcuts.
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Old 07-11-2012, 10:46 AM   #26
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Improper Grounding causing Sub woofer noise


Quote:
Originally Posted by ktkelly View Post
To the OP:

The real problem is that when you connect that RCA cable to the sub, you are connecting two different electrical circuits that have a different electrical potential. Ergo, you just created a ground loop. Your line level feed is now carrying voltage.

Free fix? Move the sub. Costly fix? Jensen ground loop isolator.



Check out Jensen. They make great "band-aids"....



This is accurate information. If the shield on the unbalanced line level cables has a slight difference in voltage potential you can pick up hum. We are talking millivolts because this is a small signal to begin with.

Even if everything is plugged into the same electrical circuit this problem can show up. Hooking up a cable signal or something from the outside aggravates this problem even if everything is grounded properly.

This is why the high end equipment uses balanced pairs for their signal wires.



Added info.....A 2 to 3 prong adaptor is a very useful troubleshooting tool for isolating the cause.

Last edited by zappa; 07-11-2012 at 10:57 AM.
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Old 07-11-2012, 11:14 AM   #27
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Improper Grounding causing Sub woofer noise


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Originally Posted by kontoose View Post
Here's an old trick. Use a U.P.S to power the audio equipment, and use "braided" over sized grounding cable running to a 10ft. 3/4 inch ground rod that is driven into the earth no closer than a 6ft. minimum distance from either the electrical panel's ground rod...or the home's water pipe...(where it enter's the ground, or runs underground).
I'll eat my hat if you have as much as a blip of a hum after that...
Did you forget to add that this rod would need to be bonded to the other electrodes for the house?
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Old 07-11-2012, 08:40 PM   #28
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Improper Grounding causing Sub woofer noise


Here are the images inside the electrical panel.

http://i.imgur.com/WhVEm.jpg
http://i.imgur.com/KJLNj.jpg
http://i.imgur.com/9oRaT.jpg
http://i.imgur.com/l7wqj.jpg
http://i.imgur.com/VQVfw.jpg
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Old 07-11-2012, 08:47 PM   #29
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Improper Grounding causing Sub woofer noise


Quote:
Originally Posted by ktkelly View Post
To the OP:

The real problem is that when you connect that RCA cable to the sub, you are connecting two different electrical circuits that have a different electrical potential. Ergo, you just created a ground loop. Your line level feed is now carrying voltage.

Free fix? Move the sub. Costly fix? Jensen ground loop isolator.
When you say 'two different electrical circuits' what are you referring to exactly?
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Old 07-11-2012, 08:53 PM   #30
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Improper Grounding causing Sub woofer noise


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Originally Posted by zappa View Post
This is accurate information. If the shield on the unbalanced line level cables has a slight difference in voltage potential you can pick up hum. We are talking millivolts because this is a small signal to begin with.

Even if everything is plugged into the same electrical circuit this problem can show up. Hooking up a cable signal or something from the outside aggravates this problem even if everything is grounded properly.

This is why the high end equipment uses balanced pairs for their signal wires.



Added info.....A 2 to 3 prong adaptor is a very useful troubleshooting tool for isolating the cause.
Can you explain how I could make use of a 2 to 3 prong adapter in this situation?

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