FAQ: Ground Loop nightmare!

[fronesis]

First, if it's in appropriate to post this here, please delete. But I'm really desperate for help, and folks here have been so knowledgeable and friendly in the past. I also posted this deep in the bowels of AVS forums, so if anyone here reads there, feel free to ignore me in one place.

I've read every thread and faq on ground loops I can find on the net, and I've got about 30 hours into troubleshooting my problem. I'm now at a complete loss, so I thought I'd put out a call for help. Help!

Situation:
- HT set up in living room of CONDO (I can't fix this at the building)
- 60hz hum coming through the RG6 DirecTV coax cable at the wall of the living room
- runs into my DirecTV receiver and then to my Yahama a700 AVR
- rest of system includes Emotiva UPA-7 amp (a700 as pre-pro), Emotiva 6.2s, ERDs, and 6.3 for speakers, and Mitsu DLP Tv; plus eD powered subs

I have clearly isolated the hum to the coax cable. Unplug it from wall, unplug it from the sat box, and noise is gone. The buzz comes when it runs to ground either through my powered subs (with 3 prong plugs) or through the UPA-7 (also 3 prong). TV, AVR, and SAT do not have grounded plugs.

I have running components off different AC outlet - no diff. I have tried running the coax through a grounding block in my utility closet (new condo), but it doesn't matter. I think the bottom line is that the coax cable has a different ground than the electricity in my apartment, and so we have a ground loop.

The only option I found was to use THIS ground isolation transformer, one of the only ones specifically designed for satellite.

It worked great for 2 months!

Then, DirecTV updated the firmware on my SAT box, and the next thing I knew I had no signal. Took out the isolator, and signal is perfect. Replace it, no signal. So now my one solution is no longer an option.

I am currently using the the workaround of isolating my video signal from my audio. So rather than running HDMI through my AVR, I am running HDMI straight from SAT to TV, and then connecting the sound to the AVR with optical digital. This works, but it is far too complicated (can't do switching through the AVR) and it prevents me from having on-screen access to my AVR, since once I connect the AVR to the TV, the ground loop is back (because the circuit has now been completing, running from SAT to TV and then to AVR and speakers).

I have two questions, one specific, one general:

1. If I had an AVR or a pre-pro with a 3 plug ground (like the UMC-1?), wouldn't the current run to ground there, before the amps or speakers, thus eliminating the hum?

2. Is there anything else I can do?

[bootman]

How did you exactly ground the block in the utility closet?
To what?

[fronesis]

How did you exactly ground the block in the utility closet?
To what?

Yes, I think the nature of that "grounding" was the reason this doesn't solve the problem in my case. I live in a brand new building, wired for FIOS, DirecTV, and Cable TV from the outiside, and internally wired with Coax and ethernet. There's a cabinet in the utility room where all those wirings meet. Coming from outside the room are the coax cables for SAT and CAT, and also a REALLY thick green sheathed copper grounding wire. That wire is run to a screw at the bottom of this thin metal cabinet, and it was connected to grounding wire coming from the Verizon FIOS modem. I think the idea is that *that* green wire is running to ground outside the building.

Inside this cabinet is also a big copper CATV switching block. It has a place for a grounding wire that was NOT connected. So I connected it by running that to the green wire, and connected it in where it already connects to the fios grounding wire. I also tried, alternatively, to rerun the green wire straight to the copper switching block.

Neither of these worked.

My guess is that this green wire is grounded outside the building *differently* than my electrical box is. The electrical box sits right next to this network cabinet in my utility room, but I know that the green wire does NOT run to the electrical box, because I can trace it to a huge utility closet on the main floor of my building, where everyone's SAT and CATV are connected. These green wires come in and out of there, and there is nothing in that utility closet for electricity.

So I think I have two grounds because that green wire ground and my electrical outlet grounds are not joined together.

But I also don't see how I personally can fix that. (I could open up my electrical box to run a ground, but I know that we NOT follow code). None of my plumbing is grounded, so I don't see how I can create a common ground. Obviously, if my theory is right, then the CATV and SAT folks might be able to fix this by making sure their ground is joined to the electrical ground outside the build, but I don't think I'll have much luck convincing them to do this on my behalf.

On the AVS thread someone suggested a bad isolator, and for now that's as good a solution as any. The isolator worked just fine at first, and so it could be that IT went bad, and not that DirecTV changed anything fundamental.

[collector]

I know this sounds inanely simple ( and maybe a bit naive), but what about a problem with the coax cable somewhere along the line?

In all you troubleshooting, you did not say whether you tested the coax cable. I have an intermittent ground hum that I can't find the issue with - I sympathize with your dilemma!!!

[fronesis]

I know this sounds inanely simple ( and maybe a bit naive), but what about a problem with the coax cable somewhere along the line?

Oh, that's certainly possible, but the problem is that the entire run of coax cable is inside the walls (all run when the building was built 5 years ago). So I suppose I could check this by buying some cable and running it from the utility room (across the floor) to the living room, but if it did indicate that the coax in the wall was bad, I'm not sure what I'd do.

I can't run a new line through the walls and I can't really run a line outside the walls (it would have to through multiple rooms, etc.).

[geebo]

Jun 4, 2011 9:00:17 GMT -5 fronesis said:

I know this sounds inanely simple ( and maybe a bit naive), but what about a problem with the coax cable somewhere along the line?

Oh, that's certainly possible, but the problem is that the entire run of coax cable is inside the walls (all run when the building was built 5 years ago). So I suppose I could check this by buying some cable and running it from the utility room (across the floor) to the living room, but if it did indicate that the coax in the wall was bad, I'm not sure what I'd do.

I can't run a new line through the walls and I can't really run a line outside the walls (it would have to through multiple rooms, etc.).

But you still need to know if the cable is your problem so you can (possibly) stop hunting for it. If it is, then you can worry about a fix.

[fronesis]

you still need to know if the cable is your problem so you can (possibly) stop hunting for it. If it is, then you can worry about a fix.

You are right, of course. And I'll try this.

If the cable is the problem, then I still think an isolator is my only practical fix. The work required to run a new line is simply inconceivable to me.

But I guess I should get my hands on 40 feet of coax and see what it reveals.

[bootman]

All catv wire needs to be properly bonded by code.

if you have a voltmeter measur how much AC you have on that line.

Call your respective service provider and tell them you have an unsafe back feed of AC coming in.

The cable company must come out and fix directly.

Sat will have had a contractor come in to wire.

regardless it is their responsibility to fix.

How much AC is on the coax?

[fronesis]

Jun 4, 2011 10:44:39 GMT -5 bootman said:

All catv wire needs to be properly bonded by code.

if you have a voltmeter measur how much AC you have on that line.

Call your respective service provider and tell them you have an unsafe back feed of AC coming in.

The cable company must come out and fix directly.

Sat will have had a contractor come in to wire.

regardless it is their responsibility to fix.

How much AC is on the coax?

I don't own a voltmeter, but I can't tell you how many times I've been in situations like this and needed one.

EDIT: I've just placed an order for one on Amazon.

If anyone is interested, I'll report back here next week on my results with the voltmeter, and with running a new coax line.

[selkec]

The cable company or sat sompany does not have to fix it directly. It is up to the customer to provide the appropriate ground. It the house does not have the correct ground with a ground rod the cable or sat company can actually refuse to do the install. The sat/ cable comnpany will use what is at the house. How do I know this you ask. I worked for Dish for 7 years and now Comcast for over 2. And grounding is a big deal to both companies. Hell try to unground the sat box and see if the hum goes away. I didnt tell you that.

[selkec]

Also your coax is most likely just fine. Cable and sat both are now very picky and if the cable is damaged you will get pixelation.

[matt]

I have had problems with coax grounding issues before:
emotivalounge.proboards.com/index.cgi?action=display&board=amps&thread=6204&page=3#271219
In my case, it involved damaged equipment, so getting the source of the problem fixed may help.

Just to help visualize your setup, I created a diagram of your setup:

No hum:
TV --HDMI-- Sat
 |
optical
 |
AVR --analog-- amp --analog-- speakers
    --analog-- sub

Hum:
Sat
 |
HDMI
 |
AVR --analog-- amp --analog-- speakers
 |  --analog-- sub
 |
HDMI
 |
TV

I am not sure if replacing the AVR with the UMC-1 will help. It appears that the hum is being transmitted via HDMI. The digital data seems to be immune in your case, but it still transfers the hum into the AVR's ground, which is likely shared between HDMI and analog audio. I suspect that if you used an HDMI extender that uses fiber only (such as the Gefen EXT-HDMI1.3-1FO) or wireless HDMI between the satellite box and AVR, you might be able to solve the interference issue.

[fronesis]

To selkec:
1) I agree: I think my coax probably is fine. But I'll test it anyway just to be sure.
2) As for it being my responsibility to provide a ground. I think that would be obviously true if I was a homeowner, but I am in a condo. And it is Comcast and DirecTV, respectively, who have wired the building. I can't "provide a ground" in my condo, because I am not allowed to make those sorts of modifications.

So I think bootman has a point. If I get a voltmeter and test the coax feed as it enters my unit, and it has AC on the line, I would be in the right to call the cable folks and tell them it's their responsibility to fix it. That doesn't mean they will listen, of course!

To matt:
1) Yes, you have diagrammed it perfectly.
2) I didn't know about fiber only HDMI. That's an excellent suggestion, and I think you are right that if I used that to connected the SAT box to the AVR, I might eliminate the problem.

Thanks so much for suggesting it!

EDIT: Oops, that Gefen part is $1500, so a much better conceptual idea than anything I could implement!

[selkec]

Jun 5, 2011 7:35:20 GMT -5 fronesis said:

To selkec:
1) I agree: I think my coax probably is fine. But I'll test it anyway just to be sure.
2) As for it being my responsibility to provide a ground. I think that would be obviously true if I was a homeowner, but I am in a condo. And it is Comcast and DirecTV, respectively, who have wired the building. I can't "provide a ground" in my condo, because I am not allowed to make those sorts of modifications.

So I think bootman has a point. If I get a voltmeter and test the coax feed as it enters my unit, and it has AC on the line, I would be in the right to call the cable folks and tell them it's their responsibility to fix it. That doesn't mean they will listen, of course!

It is not their responsibility. It it whoever owns the property to be sure sll the right ground is there. In your case the owner of your condo has to provide the correct ground at that property. Once its there. That is when the cable/sat compant will ground it. But you will nevere EVER get a company to install a ground rod or whatever. We are not even licensed to install a ground rod and backbond it. So you are wasting your time if you think you will get any service provider to put in a ground that is up to code.
Call your landlord. Tell them the place is not grounded correctly and needs to be put up to code. They will either fix it or not.
If you go bothering the service provider about the ground. YOu may end up with no service because in reality if there is not proper ground they can deny to put service in your place

[selkec]

Also you are testing for AC why??? Im not trying to be a dick here but your going to find anywhere from 13v to maybe 21v on your lines. Did you not know that satellite boxes send voltage out to the lnbs and switch boxes? This is very true. Quick way to test. Stick your toung to the line. I gaurantee you will get your tongue shocked like sticking it to a 9v battery but stronger.
NOW, if you have cable tv and are finding voltage on the line then you have a problem. With cable there is no voltage. But if you call the sat people and tell them you have voltage. They will say I hope so because without it your dish wont work.

[matt]

Jun 5, 2011 13:30:25 GMT -5 selkec said:

Also you are testing for AC why??? Im not trying to be a dick here but your going to find anywhere from 13v to maybe 21v on your lines. Did you not know that satellite boxes send voltage out to the lnbs and switch boxes? This is very true.

Then the test should be performed with the satellite box switched off, preferably turned off with a switch on the back while still plugged in. This assumes that the dish is not shared with another box.

When I encountered an improper ground with my cable, I found about 63 volts. Although this was a digital voltmeter. A better measurement would include a resistor wired in parallel with the voltmeter with a high ohm rating to measure actual current flow instead of potential current. Since it already fried my cable modem, I knew that there was plenty of current there.

What is the point? Probably just to find out how bad the situation is. Of course, if it reads close to 0 volts between the satellite box ground and coax (assuming that the satellite box is off, but still plugged in), then we know that grounding is not the issue. Probably a good test before calling the landlord.

Jun 5, 2011 7:35:20 GMT -5 fronesis said:

2) I didn't know about fiber only HDMI. That's an excellent suggestion, and I think you are right that if I used that to connected the SAT box to the AVR, I might eliminate the problem.

Thanks so much for suggesting it!

EDIT: Oops, that Gefen part is $1500, so a much better conceptual idea than anything I could implement!

That is why I also suggested wireless HDMI. Although there could be cheaper fiber only converters out there. I just happen to know that Gefen has been doing this kind of work for a while. If you do not mind polluting your radio spectrum a little, then wireless would be a cheaper way to go. I did not look around too much, but I suspect that you can probably find something in the $150 to $300 range. Here is an example: www.brite-view.com/ I would try to avoid placing the transmitter and receiver too close together. They are designed to operate over a distance.

Also, you may want to spend $10 on a receptacle tester. If there is a wiring issue, it will catch it. You can find cheap ones at Amazon, but any hardware store should have one:
www.amazon.com/50542-Receptacle-Tester-Improper-Indicator/dp/B002LZTKIA/
It is amazing what unsafe wiring those things can find. In theory, a home inspector should perform this test. I am not sure about a rental or condo. Some surge suppressors or power conditioners may perform this test, but I am not sure how thorough it is.

[fronesis]

Thanks, Matt and selkec. I'll followup when I know more.

Just to clarify with selkec:

I don't have a landlord. I own my condo.

But I do not own the entire building, and I cannot install grounding rods outside of a building that 80 people live in. I do not have the right to do anything to the exterior of the building.

On the other hand, both DirecTV and comcast have signed agreements with the condo building association that allow them to wire the building to sell their services to condo unit owners, and which require them to do so according to code. Comcast and a local DirecTV affiliate ran all the coax wire in this building and fed service to large utility closets on each floor. So while I agree with you that most cable companies would try to blow me off, I believe that legally it is, in fact, the cable company's responsibility.

And they cannot simply tell me they can't give me service. In agreeing to provide service to the condo building, they agree to offer service to every condo unit. And there is nothing about my unit that is different from everyone else's; they are all the same in a new building.

As for the SAT having AC on the line. OK, I get that. But my neighbor across the hall has a very similar AV setup, and he has no ground loop with his SAT signal. It's a new building with brand new electrics, so I doubt that the outlet is a problem, but I will check that too (since I'm checking everything). I have tried moving all the stereo equipment to a different outlet and it did not solve the problem.

To clarify further. My unit is fed with CAT and SAT lines and both have the ground loop. Also, the entire building has ONE dish on the roof, running through many switches to feed at least two dozen units.

Matt: thanks for the brite-view link - will check that out.

[fronesis]

1. The coax is fine. I ran a brand new line straight from utility closet to AV setup, with the exact same results.

2. I don't see much AC on the coax lines. On the SAT line I'm measuring about 5 or 6 volts, and on the CATV line I'm measuring less than 1 volt. Note: the CATV line, when connected to the AVR, causes just as much noise as the SAT line. And I think I'm measuring correctly since I'm getting 121 volts out of my wall electrical sockets.

But if there's no voltage on the lines, then what's causing the ground loop???

Could it be a problem with my new Yamaha a700 avr?

[selkec]

They can offer you service But in no way whatsoever can they install any type of ground rod. At least this is true for Comcst and Dish Network. All we are allowed to do it connect to whatever the builders installed. You may find some satellite contractors put in ground rods if they are old school and dont follow the rules but... Dont count on it. All the providers are responsible for it to give you service and ground it to the provided ground. If it is the correct ground. Now given that said. YOu said you live in a MDU which is a multiple dwelling unit. The rules are different then. With cable the system is grounded outside at the main box for each building. Also you have a mdu setup for your satellite the same thing is applied. All the switches and everything are ground wherever they are located but it may not be the correct ground.
Have you tried to just put in cheater plugs to get rid of the 3rd prong. That may solve the ground loop also.
Now that I think of it. I had a customer with this problem a few weeks ago in an apartment. there was no getting rid of the hum. I happened to give him a cheater plug and the hum was gone. Thats about all you can do in a MDU or condo setup.

[fronesis]

Interestingly, I was just experimenting with using cheater plugs.

Yes, if I put cheater plugs on both of my subwoofers, then the ground loop is broken (because the ground is lifted) and the buzz is gone.

Of course, everyone says it's a BAD idea, and NOT safe to use cheater plugs all the time.

I guess my next option is one of these:

1) www.sweetwater.com/store/detail/DTI/

OR

2) www.amazon.com/Ebtech-Hum-Voltage-Filter/dp/B0002E4YI8/ref=sr_1_1?ie=UTF8&qid=1307492745&sr=8-1

I think if I plug the AVR into the Hum X it might fix it.

I think if I use the hum eliminator on my subwoofer out cables, it might fix it.

Any thoughts?