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Ground loop hum

post #1 of 29
1/30/12 at 7:34am
Thread Starter 
Know there are a lot of ground loop him threads - but there are a lot of inconsistent ideas on a cure, so I wanted to try to get a consensus opinion...

My situation:
When I first hooked up my A2-300 I had a ground loop issue from the cable box. I was able to fix it by running my cable line through my surge suppressor and plugging my sub into the same outlet.

Yesterday I reorganized my room - now the equipment is not near the sub, so sharing an outlet is not an option and the hum is back.

Currently the sub connects to a panel behind the AVR via a piece of RG-6 that runs through the wall to the sub location.
Testing with a "cheater plug" eliminates the hum. Also disconnecting the sub from the AVR eliminates the hum. Running a cable direct from the AVR to the sub does NOT change the hum (so the in wall wire is not the issue). The incoming digital cable line still goes through the surge suppressor, and disconnecting it completely does NOT eliminate the hum.

What are the BEST options for fixing this without affecting the sub output? I read that the ground loop eliminator plugs have the potential to affect the frequencies going to the sub - any documented truth to that?
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post #2 of 29
1/30/12 at 7:44am
If it were me I would check the ground on the coax where it enters the home it should be grounded at the service box along with all grounds in the home. ( there should only be one main ground).
I would also get one of those plug checkers and make sure the wiring is ok at the receptacle and in normal room wiring all the plugs will be on the same circuit unless you had a dedicated circuit for your equipment.
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post #3 of 29
1/30/12 at 8:00am
Quote:
Originally Posted by PTAaron View Post

Know there are a lot of ground loop him threads - but there are a lot of inconsistent ideas on a cure, so I wanted to try to get a consensus opinion...

My situation:
When I first hooked up my A2-300 I had a ground loop issue from the cable box. I was able to fix it by running my cable line through my surge suppressor and plugging my sub into the same outlet.

Yesterday I reorganized my room - now the equipment is not near the sub, so sharing an outlet is not an option and the hum is back.

Currently the sub connects to a panel behind the AVR via a piece of RG-6 that runs through the wall to the sub location.
Testing with a "cheater plug" eliminates the hum. Also disconnecting the sub from the AVR eliminates the hum. Running a cable direct from the AVR to the sub does NOT change the hum (so the in wall wire is not the issue). The incoming digital cable line still goes through the surge suppressor, and disconnecting it completely does NOT eliminate the hum.

What are the BEST options for fixing this without affecting the sub output? I read that the ground loop eliminator plugs have the potential to affect the frequencies going to the sub - any documented truth to that?

I have had this happen before and what a nightmare. I have a 9.2 setup in my bedroom. The only thing worse then the Subs kicking on @ 3am would be me not being able to find my gun. Ohh and I had this happen twice. Based on the wife, it wouldn't happen a third time and she was right!!

In any case my issue ironically was the subwoofer cable. It was same type situation where I made moved my stuff around and it just ruined the cable. I had tried everything with no luck. Switching outlets, investigating a ground loop isolation kit. It was a newer house so I got to the point that I was going to have to check to make sure house was properly grounded.

Does your subs have the ground switch built in? Also, if you have an old rca cable laying around grab that and see if it fixes the issue. You can always grab a better one later. Ground issues are such a pain.
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post #4 of 29
1/30/12 at 11:58am
Thread Starter 
Quote:
Originally Posted by oztech View Post

If it were me I would check the ground on the coax where it enters the home it should be grounded at the service box along with all grounds in the home. ( there should only be one main ground).
I would also get one of those plug checkers and make sure the wiring is ok at the receptacle and in normal room wiring all the plugs will be on the same circuit unless you had a dedicated circuit for your equipment.

I will try to check on the ground at the house.
All of the plugs are on the same circuit in that room - and because of the way it was wired so are the lights... but there wasn't a problem after I "fixed it" as outlined earlier.
My surge suppressor indicates the status of the line - it shows that the outlet is grounded and all that, but I will look into a plug checker.

Quote:
Originally Posted by TheBrandon View Post

I have had this happen before and what a nightmare. I have a 9.2 setup in my bedroom. The only thing worse then the Subs kicking on @ 3am would be me not being able to find my gun. Ohh and I had this happen twice. Based on the wife, it wouldn't happen a third time and she was right!!

In any case my issue ironically was the subwoofer cable. It was same type situation where I made moved my stuff around and it just ruined the cable. I had tried everything with no luck. Switching outlets, investigating a ground loop isolation kit. It was a newer house so I got to the point that I was going to have to check to make sure house was properly grounded.

Does your subs have the ground switch built in? Also, if you have an old rca cable laying around grab that and see if it fixes the issue. You can always grab a better one later. Ground issues are such a pain.

I tried an external cable when I got the hum from the in wall cable, still had a hum... but I will try another cable and see if that changes things. I currently have a "High Quality" Monster subwoofer cable at the sub and a "Digital Coax" cable from the AVR to the wall panel.
I will definitely try another cable just in case
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post #5 of 29
1/30/12 at 12:32pm
Quote:
Originally Posted by PTAaron View Post

I will try to check on the ground at the house.
All of the plugs are on the same circuit in that room - and because of the way it was wired so are the lights... but there wasn't a problem after I "fixed it" as outlined earlier.
My surge suppressor indicates the status of the line - it shows that the outlet is grounded and all that, but I will look into a plug checker.


I tried an external cable when I got the hum from the in wall cable, still had a hum... but I will try another cable and see if that changes things. I currently have a "High Quality" Monster subwoofer cable at the sub and a "Digital Coax" cable from the AVR to the wall panel.
I will definitely try another cable just in case

Look around your house and see if there is more than one ground rod outside as this has caused more than one issue.
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post #6 of 29
1/30/12 at 12:37pm
Thread Starter 
Quote:
Originally Posted by oztech View Post

Look around your house and see if there is more than one ground rod outside as this has caused more than one issue.

I will do that, thank you for the idea.
If I do find more than one... what is the best course of action?
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post #7 of 29
1/30/12 at 1:02pm
You will have to link them together an electrician would probably be in order for that do to code and insurance.
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post #8 of 29
1/30/12 at 1:16pm
Thread Starter 
Quote:
Originally Posted by oztech View Post

You will have to link them together an electrician would probably be in order for that do to code and insurance.

Gotcha, thanks.
I will take a walk around the house when I get home tonight... may be hard to see with the snow we got yesterday.
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post #9 of 29
1/30/12 at 1:27pm
Thread Starter 
When I first moved in and had to "fix" the mess of wires and splitters the previous owner had set up for cable service one of the splitters that was no longer needed was connected to the copper piping with a clamp and wire going to the ground terminal on the splitter - would reinstalling that potentially help?
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post #10 of 29
1/30/12 at 1:36pm
Quote:
Originally Posted by PTAaron View Post

When I first moved in and had to "fix" the mess of wires and splitters the previous owner had set up for cable service one of the splitters that was no longer needed was connected to the copper piping with a clamp and wire going to the ground terminal on the splitter - would reinstalling that potentially help?

If that was the ground they used then yes but make sure the water pipe is also ground back at the service box ground rod if not then you have another ground loop.
You do not have to use the old splitter all splitters have a ground lug on them as a matter of fact I would not use the old one they do go bad they already drop the signal by at least 3.5db a leg on a two way more on 3 and 4 way so when they go bad that drop is more until it dies altogether
I would still look for the coax ground block where service comes in the home and run a ground if it does not have one already to the service ground rod.
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post #11 of 29
1/30/12 at 1:45pm
Thread Starter 
Quote:
Originally Posted by oztech View Post

If that was the ground they used then yes but make sure the water pipe is also ground back at the service box ground rod if not then you have another ground loop.
You do not have to use the old splitter all splitters have a ground lug on them as a matter of fact I would not use the old one they do go bad they already drop the signal by at least 3.5db a leg on a two way more on 3 and 4 way so when they go bad that drop is more until it dies altogether
I would still look for the coax ground block where service comes in the home and run a ground if it does not have one already to the service ground rod.

Yeah, sorry - I meant adding the wire clamped to the pipe back to one of the current splitters.

Thanks for the information - gives me a good starting point for trouble shooting this.
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post #12 of 29
1/30/12 at 1:51pm
Quote:
Originally Posted by PTAaron View Post

Yeah, sorry - I meant adding the wire clamped to the pipe back to one of the current splitters.

Thanks for the information - gives me a good starting point for trouble shooting this.

I had this problem years ago with an OTA antenna that had a separate ground rod about 20ft from my service ground so I got some 8guage green ground wire from Lowe's and ran it in conduit on the base of my house connecting the 2 grounds together and hum was eliminated.
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post #13 of 29
1/30/12 at 9:37pm
Thread Starter 
Okay... I didn't get to check for outside grounds - but I did play around with my system a little:

Disconnecting the cable box from the AVR did NOT make the hum go away.

I tried completely different cables and ran directly from the AVR to the sub - hum was still there.
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post #14 of 29
1/30/12 at 9:55pm
Thread Starter 
I take that back... I still had the cable line plugged into the surge suppressor when I tested it. Removing the cable line from the surge suppressor kills the hum.
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post #15 of 29
1/30/12 at 9:56pm
Thread Starter 
...and re-attaching the ground line to the splitter eliminated 80% of the hum...
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post #16 of 29
1/30/12 at 10:13pm
So your cable needs to be grounded correctly.
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post #17 of 29
1/30/12 at 10:27pm
Quote:
Originally Posted by oztech View Post

So your cable needs to be grounded correctly.

Or, alternatively, get something like this.
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post #18 of 29
1/30/12 at 10:55pm
Thread Starter 
Quote:
Originally Posted by oztech View Post

So your cable needs to be grounded correctly.

Indeed. I will get outside and check how it is grounded ASAP.

Quote:
Originally Posted by Tom Ames View Post

Or, alternatively, get something like this.

I may pick this up as well... just to be sure I am doing everything I can. The main line comes in and has a section joined to it in a very easy to reach area... that piece looks like it would fit in perfectly where the 2 lines are joined - and protect me from similar issues with my other TVs
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post #19 of 29
1/30/12 at 11:16pm
You should have one of these where the cable enters the house from the service.
http://www.google.com/products/catal...wAw#ps-sellers
Except the RG6Q model.
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post #20 of 29
1/30/12 at 11:21pm
Thread Starter 
I will have to take a look tomorrow. I found old cable lines where it apparently came into the house in the past - and the new line looks like it comes in where the AC lines come into the house...
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post #21 of 29
1/31/12 at 5:50am
Thread Starter 
This may explain a few things... What I see where the cable line enters the house is pretty simple: a wire comes out if the ground and goes into the basement along with the air conditioner lines that head to the furnace.
No grounding outside of the house - unless it happens underground... Which seems highly unlikely.

Also worth noting - the cable line comes in on the opposite side of the house from the electrical service - so connected grounds would be pretty hard to do, no?
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post #22 of 29
1/31/12 at 8:16am
I would look in the basement for a ground block usually there will be a ground bar or copper strip for connecting grounds for equipment if not I would contact a local electrician and have him put you one in that meets code. This way you will have a place to ground equipment you have now and in the future. I caution you to be careful
around electrical but if there is a bar or strip the wires would be green as to keep to code again at this point an electrician would be a safe call.
Using water pipes as grounds are not ideal do to bad or corroded connections also causing impedance differentials.
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post #23 of 29
1/31/12 at 9:47am
Thread Starter 
I appreciate your help and advice!

I already know that calling the cable company will probably just leave me with a headache, do so next step is to bring in my father in-law to look at the grounding situation. He isn't a licensed electrician, but he does heating and cooling for a living and knows way more about electrical systems and code than I will ever know. I will be ordering the Viewsonic ground loop isolator too... but I will be working hard to make sure the system is correctly grounded as well.
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post #24 of 29
1/31/12 at 9:52am
Quote:
Originally Posted by PTAaron View Post

I appreciate your help and advice!

I already know that calling the cable company will probably just leave me with a headache, do so next step is to bring in my father in-law to look at the grounding situation. He isn't a licensed electrician, but he does heating and cooling for a living and knows way more about electrical systems and code than I will ever know. I will be ordering the Viewsonic ground loop isolator too... but I will be working hard to make sure the system is correctly grounded as well.

I think that is a wise decision.
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post #25 of 29
1/31/12 at 3:20pm
I had a hum problem with a new sub. I turned out that removing the ground from the sub power cable cured it 100%. I reviewed all of my components and found it was the only device with a grounded plug. All other components used a polarized (one lug bigger than the other) power cords.
Hope this helps...
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post #26 of 29
1/31/12 at 4:11pm
Thread Starter 
That's what I'm trying to avoid doing - the general advice is that it is a bad idea to remove a ground from a device that was meant to be grounded. There are actually a few threads with some heated debates on the topic - but if possible I would like to keep the sub grounded, since that's the way it was designed.
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post #27 of 29
2/3/12 at 6:55pm
Thread Starter 
Viewsonic ground loop isolator arrived already - that was ridiculously fast shipping!

Question for you guys: should I put it in before the first split in the system or just put it on the line going to the media room?

My thought is that it should go before the main split - since it supposedly doesn't interfere with internet an other features...
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post #28 of 29
2/3/12 at 8:02pm
Thread Starter 
...and the very quiet hum that remained after grounding out the cable line to a pipe is unchanged by adding the Viewsonic piece.
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post #29 of 29
2/3/12 at 8:31pm
Quote:
Originally Posted by PTAaron View Post

...and the very quiet hum that remained after grounding out the cable line to a pipe is unchanged by adding the Viewsonic piece.

You may have more than one issue with your electrical so an electrician is still a safe bet also using ground lifts and modified plugs are bandaids where a stitch should go. I would invest in a plug checker just for your peace of mind and make sure all your receptacles are correctly wired.
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