# HDMI ground loops?



## tnargs (Sep 7, 2006)

Hi,

I have ground loop hum and am busy checking potential loops.

One thing I see is six HDMI cables connected to my AVR (4 sources, 2 displays). Three of these six devices are mains-earthed. Which says to me there are 3 redundant earth loops I would like to isolate.

If these were all analogue RCA connections I would break the signal earth shield lines for these 3 mains-earthed components. But I don't know what to do about them being HDMI.

Questions:

Am I right, can HDMI cables cause earth loops? Or are they isolated from each other and from chassis earth in a mains-earthed component?

Is it advisable to cut the earth wire in an HDMI cable if components at both ends have chassis earths? If so, how (which wire)?

Is there some other way to isolate the earth line on HDMI connections?


----------



## TypeA (Aug 14, 2010)

Opps wrong thread, wish I had some advise for you. Let us know what you find out.


----------



## wgmontgomery (Jun 9, 2011)

Hi. The best way is to just disconnect each HDMI cable one-by-one, but I doubt that the hum is caused by the HDMI cables. In general, the most likely sources would be the subwoofer or the cable (as in cable TV).

Pins 1 through 9 carry audio and video (TMDS data channels), three pins per channel. Each channel has three separate lines for + values, - values, and a ground or data shield

FWIW-here are the pin locations for HDMI


----------



## tnargs (Sep 7, 2006)

Hi Gary and thanks. It is reassuring to hear the HDMI is probably not causign a ground loop.

I will pay attention to the sub amp connections as you suggest.


----------



## wgmontgomery (Jun 9, 2011)

tnargs said:


> Hi Gary and thanks. It is reassuring to hear the HDMI is probably not causign a ground loop.
> 
> I will pay attention to the sub amp connections as you suggest.


No problem. 

Please note that the HDMI connections are _probably_ not the cause; they could be, but I would check the subwoofer and cable TV connections first. Also, the subwoofer may have a "ground lift" switch on the back; most of them do. If it does, try that.

If those are not the cause, try unhooking the HDMI (and other cables) _one at a time _until you find the problem. Let us know if you still have problems.

BTW-are the components connected to a power conditioner, surge protector or power strip? You will have less chance of noise if everything uses a common power outlet. That's not always possible, but it's ideal...as long as you don't "overload" the outlet.


----------



## tnargs (Sep 7, 2006)

wgmontgomery said:


> ....BTW-are the components connected to a power conditioner, surge protector or power strip? You will have less chance of noise if everything uses a common power outlet. That's not always possible, but it's ideal...as long as you don't "overload" the outlet.


Yes, I am using a pro audio 16-outlet power strip for all components except the projector, which is plugged into a ceiling outlet and runs HDMI to the AVR.


----------



## lcaillo (May 2, 2006)

Most ground loops are due to source lines like cable or sat systems that are not earthed to the same potential as your electrical system. Also, make sure that every power cord is plugged in to the same circuit if possible. Verify the grounding on all circuits. 

Never lift a ground to relieve a ground loop, except for testing. Ground everything properly and remove defective components.


----------



## tnargs (Sep 7, 2006)

lcaillo said:


> Most ground loops are due to source lines like cable or sat systems that are not earthed to the same potential as your electrical system. ....


Yes, I have an antenna TV system with a masthead amp and several outlets around the home. I will look into it. thanks


----------



## lcaillo (May 2, 2006)

Make sure that it is grounded to the electrical system ground electrode and your connections are tight and not oxidized. Also, if you are using a preamp, the power supplies often leak or create ground currents.


----------



## wgmontgomery (Jun 9, 2011)

wgmontgomery said:


> Hi. The best way is to just disconnect each HDMI cable one-by-one, but I doubt that the hum is caused by the HDMI cables. In general, the most likely sources would be the subwoofer or the cable (as in cable TV).


----------



## lcaillo (May 2, 2006)

tnargs, did you solve the problem?


----------

