Ground hum ?

[kiwiaudionut]

Connected all my home theater gear up last week with no issues at all and was watching dvd,s through my new projector.

This week i added an At&t Uverse receiver that is connected throughout my house with RG6 coax. It is using HDMI for video only to the projector, and optical digital to my processor for audio.
I immmediately had a ground hum through every speaker, or what sounds like one, and started pulling connections to find the culprit.
I had the power wire and optical wire removed from the AT&T box, leaving only the coax and HDMI, and still had the noise.
If I pull either of the latter, the noise goes away.

Remember, i only have the HDMI for video to the projector, so how it is transmitting this audio noise I dont know ??

AT&T spent a lot of time reterminating every coax connection in my house and they did an excellent job of it, but still that must be the problem area don't you think?

I'm wondering what my options are. The AT&T receiver will accept cat5e so do you think if i convert the line to this from coax to cat5e ?? I don't have a problem elsewhere in the house, but every other connection is just a regular TV only and i cannot detect any extraneous noise from them.

Is there a ground loop isolator made for coax issues ?

I'm thinking a call to AT&T might be in order !

 

[TLS Guy]

Connected all my home theater gear up last week with no issues at all and was watching dvd,s through my new projector.

This week i added an At&t Uverse receiver that is connected throughout my house with RG6 coax. It is using HDMI for video only to the projector, and optical digital to my processor for audio.
I immmediately had a ground hum through every speaker, or what sounds like one, and started pulling connections to find the culprit.
I had the power wire and optical wire removed from the AT&T box, leaving only the coax and HDMI, and still had the noise.
If I pull either of the latter, the noise goes away.

Remember, i only have the HDMI for video to the projector, so how it is transmitting this audio noise I dont know ??

AT&T spent a lot of time reterminating every coax connection in my house and they did an excellent job of it, but still that must be the problem area don't you think?

I'm wondering what my options are. The AT&T receiver will accept cat5e so do you think if i convert the line to this from coax to cat5e ?? I don't have a problem elsewhere in the house, but every other connection is just a regular TV only and i cannot detect any extraneous noise from them.

Is there a ground loop isolator made for coax issues ?

I'm thinking a call to AT&T might be in order !

The installers did not do a good job they did a lousy job, most likely, unless your house has a bad house ground. In any event they went home and left you with at least one ground loop and likely more.

Right on the AT & T site there is a note to installers about tying their system to the house ground at entry.

They must bond the cable to your house ground with a grounding block at the point of entry to your home. The ground will be at your panel.

Now, it does not say this on their site, but I can tell you from experience the cable must enter your home within 20 ft of the panel. If it does not they will have to move the entry point of the cable into your home. This is all code by the way, and anything less is a violation of electrical codes.

Make them bond their cable to the house ground with gauge 4 copper. This gauge of copper is above electrical code, but it's TLS Guy's code.

It may be your house ground is inadequate also. The grounding rod must be in a moist area and be at least seven feet in the ground. I personally use three seven foot copper rods. Again this is above electrical code and is TLS Guy's code.

Ground loops are caused by potentials between ground. So if the chassis of units are at different potentials currents will flow through the grounds and create hum. So the above advice will get your house ground and the AT & T cable ground at the same potential.

Now since you have coax (cat 5 will be the same, probably worse because the ground is smaller) going all over the house, you still may have a problem.

Since your system is interactive I don't know if you can use a cable ground isolator, probably not, but ask AT & T.

The problem will come from units connected to your cable system in your house more than 20 ft or so apart and that have any units at that location with three pin AC grounding plugs. The problem will come as at those distances there will be a difference in the resistance of the coax shield and your copper house grounding wires. This will cause a ground loop and hum.

I have this problem at my house with the Direct TV system.

Here is my grounding block.

The panel is on the other side of the wall.

Here is the phone line tied in at entry.

The grounding rods the other side of the wall.

With Direct TV you can not use ground loop isolators.

I have a problem as there is FM coax and two satellite cables going to my studio and to a small system on the first level. These installations are a long way apart, three floors apart and the other side of the house. That leaves me with the unsatisfactory option of having to lift the grounds of all units on that smaller system, so it has to ground via the FM antenna cable and the two satellite coax cables. Not the best, but there is no other way.

If you can use a cable ground loop isolator use them on the feeds to systems more than 20 ft away from your main installation.

Show this post to the installers. My experience is that installers have no clue about ground loops.

 

[kiwiaudionut]

Thanks TLS Guy, thats some good info there and you have educated me.

I had forgotten my Newpoint Surge protector had inputs and outputs for coax and tried them last night, but no dice. (I have the Newpoint running through an Adcom AC enhancer also and before this issue, everything was dead quiet !)

After reading your post, I can see why and I have an idea what must be done now. Before i decide whether to call AT&T or install a ground circuit like you have, could you elaborate on one point for me please.
You said :
They must bond the cable to your house ground with a grounding block at the point of entry to your home. The ground will be at your panel.

Now, it does not say this on their site, but I can tell you from experience the cable must enter your home within 20 ft of the panel. If it does not they will have to move the entry point of the cable into your home. This is all code by the way, and anything less is a violation of electrical codes.

When you are talking about the "panel", do you mean AT&T's entry point panel or the houses main electrical panel. If you mean to tie into the main electrical panel ground rod, that is not going to happen - it is as far from the AT&T entry point as is possible on my house 80-100'.

I can however do as you did with a ground block and 4ga copper to a driven rod right outside the entry point. The cable does enter the basement within 5 ft of their panel and starts its distribution from there. My theater room is coincidentally in the basement and is the closest room to this point.

To start with, i should look inside the AT&T box to see if they did anything like this right? From what you say, chances are good they did not.

Incidentally, people are amazed when i tell them this, but we do not have electrical or building codes in my city/county ! The next county up from me has one of the strictest in my State !
I do home remodeling and the only utility company requiring inspections here are the gas company for water heaters, furnaces etc.
Builders generally love it, consumers generally do not !

 

[TLS Guy]

Thanks TLS Guy, thats some good info there and you have educated me.

I had forgotten my Newpoint Surge protector had inputs and outputs for coax and tried them last night, but no dice. (I have the Newpoint running through an Adcom AC enhancer also and before this issue, everything was dead quiet !)

After reading your post, I can see why and I have an idea what must be done now. Before i decide whether to call AT&T or install a ground circuit like you have, could you elaborate on one point for me please.
You said :
They must bond the cable to your house ground with a grounding block at the point of entry to your home. The ground will be at your panel.

Now, it does not say this on their site, but I can tell you from experience the cable must enter your home within 20 ft of the panel. If it does not they will have to move the entry point of the cable into your home. This is all code by the way, and anything less is a violation of electrical codes.

When you are talking about the "panel", do you mean AT&T's entry point panel or the houses main electrical panel. If you mean to tie into the main electrical panel ground rod, that is not going to happen - it is as far from the AT&T entry point as is possible on my house 80-100'.

I can however do as you did with a ground block and 4ga copper to a driven rod right outside the entry point. The cable does enter the basement within 5 ft of their panel and starts its distribution from there. My theater room is coincidentally in the basement and is the closest room to this point.

To start with, i should look inside the AT&T box to see if they did anything like this right? From what you say, chances are good they did not.

Incidentally, people are amazed when i tell them this, but we do not have electrical or building codes in my city/county ! The next county up from me has one of the strictest in my State !
I do home remodeling and the only utility company requiring inspections here are the gas company for water heaters, furnaces etc.
Builders generally love it, consumers generally do not !

I do mean your main electrical panel. If the grounds are tied together at entry you won't be out of trouble.

You can try and use massive separate grounds for both, but it probably won't work. So you will likely be forced to have the AT & T cable enter were it should. A house should have one ground. This is very important, and is the major reason for your problem.

I just had fiber put in and the company were careful to get the grounding right, as these issues cause their own equipment to malfunction as well as customers.

 

[kiwiaudionut]

Oh man, that is not what i wanted to hear - AT&T is going to want to try every shortcut in the book before they move their entry point and i wouldn't blame them. My Main electrical panel is on a garage wall on the extreme other side of a two story house with a fully finished basement, which means no direct access without tearing out drywall.
Initially I thought i could drive a rod by the cable access point, ground their cables to it and then run a ground wire around the exterior of the house to the electrical panels ground rod. If I interpret your theory correctly, this will be an unequal ground length circuit and i'll still have the problem ?

 

[TLS Guy]

Oh man, that is not what i wanted to hear - AT&T is going to want to try every shortcut in the book before they move their entry point and i wouldn't blame them. My Main electrical panel is on a garage wall on the extreme other side of a two story house with a fully finished basement, which means no direct access without tearing out drywall.
Initially I thought i could drive a rod by the cable access point, ground their cables to it and then run a ground wire around the exterior of the house to the electrical panels ground rod. If I interpret your theory correctly, this will be an unequal ground length circuit and i'll still have the problem ?

You are correct. The wire between the grounds would be against code if you had them.

I would try and see what happens with really good independent grounds to the AT & T box and make sure your house ground is really good a lot are not.

If you have a problem, ask At & T if their system will work with ground loop isolators inserted.

If you can't use isolators and you have a problem with independent grounds, and you very likely will. I would move the AT & T entry point to the electrical panel and then run the wire from their box, moved to the panel area, around the house to a convenient entry point. That point would be where their box now is I suspect. I had this problem in my residence in Grand Forks, and the later solution worked well.

You have to try and solve this if isolators won't work, as your only other option is to leave every system in you house that uses that AT & T hub ungrounded, by using cheater plugs. This is not a solution you want.

Our telephone company are really up on this, (Paul Bunyan coop). They have been hooking up everybody on fiber and are nearly done. They have insisted that every customer has his phone point of entry right by their electrical panel. Not doing so causes problems for their customers and them. So they are correct to insist on this as a condition of service, as not doing so can degrade everyone's service.

They are also making sure house grounds are adequate. I'm glad to say mine passed muster!

 

[kiwiaudionut]

Ok, I really appreciate your help. I'm going to dump this in AT&T's lap and see what develops. It is their problem after all, if they are not going to install where they should right !

 

[TLS Guy]

Ok, I really appreciate your help. I'm going to dump this in AT&T's lap and see what develops. It is their problem after all, if they are not going to install where they should right !

That is correct. However dealing with a big corporation and a small coop is like night and day.

With Direct TV the techs, who belong to some outfit in Oklahoma, are not well educated. I have not run into one who has heard of a ground loop and does not know what it is. Of course that meant I had to redo their work myself. They left with my systems making a huge roar. Since I knew what I had to do I did it myself.

With PB, all of their crew seem well versed on ground loops and how to prevent them. When they saw my set up, they had a senior engineer come out before installation to discuss the installation and especially grounding issues. Of course since the plans were well laid, the installation 10 days ago went without a hitch.

Unfortunately, I would bet when you deal with AT & T you will have a hard time finding anyone who knows what a ground loop is and even less likely to find someone who knows how to eliminate them. That will be your biggest problem.

That will be especially true if you are in an areas with no code inspections. The electrical inspector round here is a very knowledgeable young man, and does not let anyone get by with sub standard stuff. But he is also helpful and I good some good advice form him in the construction of this studio and other matters.

 

[Rickster71]

Adding a bit if I may:

One issue is that the low voltage guys, (read phone and cable) can't legally work inside an electrical panel to tie into the ground bar there.
So the closest to the panel they can get will be where the ground wire comes out of the meter pan and down to the ground rod(s)

Who knows what you've got there; since we don't know how much of your system is to code.
I always use something like this on all ground connections: http://www.idealindustries.com/prodDetail.do?prodId=noalox&div=5&l1=accessories
Otherwise, over time too much resistance builds up.

 

[sawzalot]

Adding a bit if I may:

One issue is that the low voltage guys, (read phone and cable) can't legally work inside an electrical panel to tie into the ground bar there.
So the closest to the panel they can get will be where the ground wire comes out of the meter pan and down to the ground rod(s)

Who knows what you've got there; since we don't know how much of your system is to code.
I always use something like this on all ground connections: http://www.idealindustries.com/prodDetail.do?prodId=noalox&div=5&l1=accessories
Otherwise, over time too much resistance builds up.

That is a very accurate statement in regards to our local cable/phone vendors, they will not ground to anything but the copper ground wire at the ground rod below the exterior meter cabinet.

 

[TLS Guy]

That is a very accurate statement in regards to our local cable/phone vendors, they will not ground to anything but the copper ground wire at the ground rod below the exterior meter cabinet.

That is the best place to ground it anyway. The house ground should be near the panel.

 

[kiwiaudionut]

That is a very accurate statement in regards to our local cable/phone vendors, they will not ground to anything but the copper ground wire at the ground rod below the exterior meter cabinet.

That is all i could expect of them anyway, and although they are due here in 10 mins. i won't get that out of them, i about guarantee it, as they would have to reinstall everything to the other side of my house.

We'll see !

 

[kiwiaudionut]

Well, the noise is gone, but i'm not sure the best method was used to get the desired results. First thing we did (AT&T dude and me) was to replace the copper ground run from their service box to the rod, which made no difference at all.
He then replaced the power supply/battery backup with a 2 wire unit eliminating the ground, which means power to the "gateway", that is AT&T's distribution router, now has no ground, but the coax runs do !
This cured my noise but at what cost ? The coax has its own path, but I now have ethernet runs and phone runs coming out of the gateway that are not grounded now right ?

Anyone think this is a big deal ?

 

[kiwiaudionut]

OOps ! upon closer inspection the small power wire coming out of the backup power supply supplying the AT&T gateway is the same 2 conductor wire that was there before, so the only change is the power wire from the receptacle to the power supply is now a non grounded 2 wire plug.
Essentially, the only change then is that the ground to the power supply is now lifted !!

 

[TLS Guy]

Well, the noise is gone, but i'm not sure the best method was used to get the desired results. First thing we did (AT&T dude and me) was to replace the copper ground run from their service box to the rod, which made no difference at all.
He then replaced the power supply/battery backup with a 2 wire unit eliminating the ground, which means power to the "gateway", that is AT&T's distribution router, now has no ground, but the coax runs do !
This cured my noise but at what cost ? The coax has its own path, but I now have ethernet runs and phone runs coming out of the gateway that are not grounded now right ?

Anyone think this is a big deal ?

It is grounded. The service box is connected to the grounding rod. The mains earth from the three pin plug and the wire to the grounding rod was your ground loop. You had one too many grounds.

That is why it is so hard to help people with ground loops on a forum. There is just no substitute for actually having everything in front of you.

It did not enter my head that you had a three pin optical converter box. Mine is two pin. That is the way it should be. Just like this.

This just reinforces the fact that EVERY member here who owns equipment, really has to understand ground loops and how to eliminate them.

 

[kiwiaudionut]

Damn, the noise came back ! Why would it do that ? It was gone for all of 2 weeks approx. and then it is back !

Not sure it is quite as loud as before, but that might just be wishful thinking on my part. Definitely related to the Uverse coaxial cable though - I pull it out of the receiver in my theater and its gone !

Interestingly, it will also go away if i pull the coax from the DVR upstairs, but all the receivers talk with the DVR in the uverse system. I have 5 receivers but they are not downstream from it. The DVR can be placed anywhere on the coax run in the home and they will all communicate.

Update: I got to thinking - what have I changed in this time period. Well, my Mitsubishi DLP died and I have a new Samsung plasma set upstairs connected to the DVR with HDMI and it has a 3 prong power cord ! If I unplug this sets power cord, the noise in my theater goes away. If I unplug this sets HDMI, the noise in the theater goes away. At no time however can the noise be heard from the Plasma set itself, or for that matter from any of the other TVs in the house. Could be the theater equipment is just more sensitive ?

So what - the extra ground this new sets power cord has introduced is causing a loop?
I used a cheater plug on the Plasma to remove the ground, and the noise is gone !
This just aint right

I wonder why the grounded power cable for my projector in the theater isn't causing problems. Come to think of it, it was creating some noise in the short time before I moved its power supply to the surge protector/AC enhancer.