# Another Ground Loop Thread..Please Help



## ccap (Feb 7, 2010)

Ok here's the situation. 

Getting hum through all my speakers. I troubleshooted and it's the hdmi cables coming from htpc, oppo and projector because they have a ground on the power plugs. The xbox and roku are fine, no ground. 

If I disconnect the plug from the oppo for example and leave the hdmi connected hum goes away as we all know. Or if I jump out the ground, hum gone. I also found a hum coming through the cable lines and I added isolators and that worked. I'm also getting it from the projector hdmi again due to the ground.

All my equipment is in a rack and plugged into a middle Atlantic strip and into one outlet. Also my amps are in the basement, but I know that it's not the preamp and amps. No hum when the sources are disconnected. I do not think this plug is a dedicated circuit, however it tried a dedicated plug in the other room and the hum is still there. Any help would be appreciated. I am at my wits end. Thanks


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## dougc (Dec 19, 2009)

I fixed mine by plugging the HTPC into a different outlet


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## ccap (Feb 7, 2010)

I have tried that and it did not work. What ever has a ground on it I get hum. The oppo blu ray, HTPC, projector. I have tried putting the oppo or htpc on a separate outlet and no luck.


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## lcaillo (May 2, 2006)

What external connections do you have going into the system? Network, cable, sat, antenna?


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## ccap (Feb 7, 2010)

lcaillo said:


> What external connections do you have going into the system? Network, cable, sat, antenna?


HI,

My connections are 
HTCP
Oppo Blu-Ray
Roku
Xbox
Cable TV
Projector HDMI

I added the blocks on the CATV lines for the Cable box and the HTPC and that stopped the Hum coming from there.

The X-box and Roku, no issue because of no ground.

The others because of the ground. I put the cheater plug on the power strip and into the wall, hum gone. so its being fed from the outlet and into the system.

Thanks


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## ccap (Feb 7, 2010)

Bump.. Trying to figure this out. 

One thing I was able to do is trace the electrical lines. They run from a sub panel, which is grounded properly to the main panel. Then it runs to my rack downstairs which houses my amps they are tied to a Richard gray power unit. Then the power runs to my rack in my theater and my projector box. It's all on the same feed.

Does this help in helping me get rid of my ground loop?

Thanks


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## lcaillo (May 2, 2006)

Start by fixing the cable ground. You should not have to isolate it. Measure the resistance in all ground paths. Somewhere it will be more than a few ohms.


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## ccap (Feb 7, 2010)

I just bought a couple of the hum x outlets. They killed my hum and noise problem and do what is advertised. They work greak


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## prerich (Mar 26, 2008)

ccap said:


> I just bought a couple of the hum x outlets. They killed my hum and noise problem and do what is advertised. They work greak


I was just going to recommend a Hum X. I bought one about 3 weeks ago, they work as advertised:T!!!


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## tcarcio (Jun 27, 2007)

I didn't even know about these things so thanks for posting it. Here is a link if anybody else is interested.
http://www.google.com/aclk?sa=l&ai=...A=details&Q=&sku=365781&is=REG&BI=225&kw=EBHX


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## lcaillo (May 2, 2006)

The best solution is to fix the ground loop by reducing excess impedance in the various grounds. In almost all cases, there is a problem in the installation somewhere that can be resolved to fix the issue. In some cases it is difficult to do so because of long ground paths between systems and circuits.

If you can't fix it at the source, something like Hum X might be a solution, but note that it is only rated for 6 amps.


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## ccap (Feb 7, 2010)

Correct on the 6 amps, but I am only using for source equipment and a projector. Not Amps


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## prerich (Mar 26, 2008)

ccap said:


> Correct on the 6 amps, but I am only using for source equipment and a projector. Not Amps


same here, I only use it for the HTPC.

Sent from my iPad using HTShack


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## gazoink (Apr 17, 2013)

ccap said:


> Correct on the 6 amps, but I am only using for source equipment and a projector. Not Amps


Pretty sure he meant 6 Amperes, not 6 Amplifiers! 

Hard to tell from what's posted, but would I be correct in stating that your AVR doesn't have a 3-pin grounded plug? And that all the sources that cause your hum do have 3-pin grounded plugs? Just a guess, based on what gear you said doesn't cause the hum.


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## ccap (Feb 7, 2010)

Yes my AVR has a 3 prong plug. It's a Marantz AV 7701, but it is not picking up the ground loop. It's only the devices that have a ground pin that are plugged into the AVR with an HDMI cable that are causing the hum. It's real strange


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## gazoink (Apr 17, 2013)

ccap said:


> Yes my AVR has a 3 prong plug. It's a Marantz AV 7701, but it is not picking up the ground loop. It's only the devices that have a ground pin that are plugged into the AVR with an HDMI cable that are causing the hum. It's real strange


Not all that strange. 

See if you can find a 3-pin to 2-pin adapter at a hardware store. That effectively lifts the ground pin on whatever device is plugged into it. Try using that with the AVR to see if the hum problems go away. If so, then try it with each source that has a third pin to see if you can find the offending unit.


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## lcaillo (May 2, 2006)

Measure the resistance between the various grounds. Find the line that has the highest resitnace and start there.


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## gazoink (Apr 17, 2013)

lcaillo said:


> Measure the resistance between the various grounds. Find the line that has the highest resitnace and start there.


Measuring DC resistance of grounds won't tell you much. Most AC leakage ground currents are capacitively coupled at some point.


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## ccap (Feb 7, 2010)

gazoink said:


> Not all that strange. See if you can find a 3-pin to 2-pin adapter at a hardware store. That effectively lifts the ground pin on whatever device is plugged into it. Try using that with the AVR to see if the hum problems go away. If so, then try it with each source that has a third pin to see if you can find the offending unit.


I have tried that. If I put on the two prong plug on my oppo blu ray, the hum goes away, same with projector and htpc. So they all have some type of ground loop issue. 

Now I never tried putting on the two prong plug on the AVR. I figured that since I found the three offending units, then it wouldn't matter.

Is there another specific process I should try?

Thanks


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## lcaillo (May 2, 2006)

gazoink said:


> Measuring DC resistance of grounds won't tell you much. Most AC leakage ground currents are capacitively coupled at some point.


Actually, inpractice it can often tell you a lot. Many of these issues are simply caused by a cable or sat system that is not grounded properly. It is a good starting point and when I was in the service and installation business I solved virtually all of these kinds of problems with information gathered with d.c. resistance checks. It depends on the nature of the problem, but if central point grounding is solid many of the problems simply go away.


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## gazoink (Apr 17, 2013)

ccap said:


> I have tried that. If I put on the two prong plug on my oppo blu ray, the hum goes away, same with projector and htpc. So they all have some type of ground loop issue.
> 
> Now I never tried putting on the two prong plug on the AVR. I figured that since I found the three offending units, then it wouldn't matter.
> 
> ...


No, floating the ground pins will tell you where the problem is. But try one device at a time connected to the AVR and then lift the AVR ground, and the device ground. You're looking for the "quiet" combination, then add other devices one at a time, grounded or not.


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