Nasty Ground Loop - tried everything

**dyazdani** · 03 December 2005, 19:19 Saturday

Try disconnecting the digital Toslink connection from your Dish receiver to your pre/pro and connecting the analog RCAs. See if the noise goes away.

I had the same problem on mine with the digital audio connection. It was like that for the first little bit, but then it just went away. Very, very strange.

Also, is this a new installation? If so, check the coax from the dish itself coming into the house. If they used a coupler or distribution block, I think it's supposed to be grounded also. My ground came loose once (they attached it to a spigot outside) and it caused trouble.

**dyazdani** · 03 December 2005, 19:21 Saturday

BTW if this is at your Arkansas location, I may be able to take a look. I live in the SE portion of the state...

**Stoney** · 03 December 2005, 20:08 Saturday

If I understand correctly, ground loops are caused or agrivated by having different pieces of equipment tied to different ground potentials. I have had chassis on different pieces at as much as 60V difference from each other (cable box and amplifier), so it would be wise to unplug power before doing any of this.
The goal is to bring all the chassis on all equipment to the same potential; if you read between them with a volt meter, you should read 0 volts.
Check your power outlets to make sure the polarities are correct (hot and neutral are not reversed).
If any of the equipment in question has non-polarized plugs, try reversing them.
Try grounding the satellite dish system to the house ground instead of a ground rod or stand pipe (unless your house power is tied to the same point). If you have an outdoor socket, connect the ground block of the dish cable to the center screw on the outlet. If you have no outlet outside, connect the chassis of the cable box to the center screw on the house outlet. If that is not possible, connect the ground on your amp to the chassis on the dish receiver.

**SteveL** · 03 December 2005, 20:15 Saturday

Good info, guys. The dish is a semi-new installation. I've had Dish for about 4 years, but recently added HD, and they had to make some modifications. I have no ground-loop noise anywhere else in the house, just in the home theater.

I'll try swapping out the digital connection, and yep - it's at the NW AR house... SE AR? Wow - that'd be a trek -- I'd definitely have to take you out to dinner and compensate you with some gas $$.

Stoney: good idea on the chassis and grounding it. I'll definitely give it a shot. Grounding the dish itself may be nearly impossible, due to where it's mounted. I live in a really hilly/tree-covered area (my pines are 100+ ft), so dish location optimization is pretty impossible. As a result, running a ground to something is also next to impossible without some *major* work.

I should also add that all of the components are grounded to the same source - I just built the theater, and all of the wiring is grounded to the same location on my subpanel, which is grounded to the house-ground. The audio equipment is all on the same 20A circuit, save for the subs, which are on their own 30A circuit, but both circuits share the same ground.

Thanks again, guys. I'll update you tomorrow (we're having 8 people over for a movie night in the 'ole Theater tonight).

**Stoney** · 03 December 2005, 20:21 Saturday

Sorry Steve, I made some edits after your reply.

**dyazdani** · 03 December 2005, 20:21 Saturday

My parents live in Bella Vista, too bad you didn't post last week. I was up there over Thanksgiving!!!

**mitch57** · 03 December 2005, 21:21 Saturday

I had a similar problem with Direct TV. I switched from Dish non HD with no ground loop issues and went with Direct TV with HD DVR and suddenly I had a MAJOR ground loop issue. I ran a ground wire from the DVR to my power amp and it completely silenced the ground loop.

I would like to find a cleaner solution to this problem though. I hate having that stupid ground wire connected to my $4000.00 amp. :cry:

**bigburner** · 03 December 2005, 23:07 Saturday

Have you guys read this article which was posted to Club Rotel by csuzor?

SMR Home Theatre

http://www.smr-home-theatre.org/Ground-Loops/

**Azeke** · 03 December 2005, 23:19 Saturday

Here is another article, I can't recall the author, my apologies if he/she reads it.

Earth Pin and Ground Issues explained:

"The "third prong" is the electrical safety ground and is there to protect you and anyone who uses your equipment from electrocution. The safety ground is a cold conductor designed to provide a path to ground for safety protection against internal shorts inside your equipment when equipped with the three prong plug.

The third prong connects back to your service panel (where it is bonded to the neutral wire), and from there is connected either or both to your house plumbing or external ground rod.

On equipment with a third prong, the metal case and external metal parts are all connected to this safety ground when you plug the electrical cord into the wall. If a component fails inside a piece of equipment and the 120 volts shorts to the equipments case, then that case is now live and can electrocute you. If the safety ground was attached, then a breaker would trip to indicate you had a fault.

On equipment with two prong plugs, they are internally insulated from the external case to provide this protection without the third wire.

If a device has a two prong power cord, it is not connected to the safety ground in your house.
The two prong plug has a one of the two "blades" of its plug wider than the other. This is the neutral return - not a ground.

If a device, designed for a three prong plug, is modified by removing the safety prong of the plug or by using a cheater (which effectively removes the third prong), then you have created the unsafe condition I mentioned above.

If you have a hum from an amplifier caused by a ground loop, then removing the safety ground connection to amplifier (and perhaps other devices as well), can clear the resultant effect of the ground loop, but creates the safety issue. It's more advisable to try and clear the condition causing the ground loop than to mask its effect by applying unsafe practices.

In that regard though, ground loops are sometimes a difficult task to track down and remove because there are a million reasons for them to exist. The loop is caused by a difference in the ground potentials in your system. Breaking the safety ground almost as often clears the problem, and that is why it goes away with the use of two prong power cords or with the use of cheater plugs. This easy fix is obviously tempting, since it's so easy. I hesitate to say that sometimes it's the only thing in the end that works on some troublesome equipment, ensuring that cheated piece of equipment is hidden away from anyone touching it.

Generally a ground loop can be tracked down to its source. Removing the problem can sometimes be a little more difficult.
You have to first ensure you have a ground loop situation and it would appear you've accomplished that.

One of the other major culprits in creating ground loops is the use of more than one circuit in an HT system. The larger systems demand more power, so several dedicated circuits are sometimes needed. But even using a single circuit with different receptacles can cause a ground loop.
Residential houses use 240 volt "single phase" three wire power. The two "hot" legs are 120 volts and are 180 degrees out of phase. The loads in your house are balanced between these two legs at the service panel. It is advisable, if you do have two circuits powering your HT system, to ensure you are using a common leg. It is fairly easy to establish this.

Let me explain a bit about ground loops.......Even though the safety ground is a cold conductor, it can, and usually does, develop a small potential, through mutual inductance, wire resistance and various other reasons that can be different at each receptacle in your house.

When I plug a power amp into one receptacle and a preamp into another receptacle, the metal cases of these two units can have a small potential difference in their safety grounds which means that this equipment's metal cases are at a slightly different potential. When I connect a single ended (RCA) cable between these two devices, a small AC current can flow in the shield because of the potential difference. This signal is in the signal loop circuit and can cause a hum. An interconnect circuit has a loop path (completed circuit) that flows through the centre conductor of the interconnect cable and back on the shield. If there is an AC signal on the shield flowing because of the ground difference potential, you'll hear a hum. Breaking the safety ground of one of the two devices removes the potential and the path for the unwanted signal flow..."

Good luck and keep us posted,

Azeke

**bigburner** · 03 December 2005, 23:56 Saturday

Azeke, that was posted by brucek.

I took a few of brucek’s posts and combined them into post #3 at http://www.htguide.com/forum/showthr...670#post206670

I haven’t read every post ever made to HTG but from the posts I have read brucek is the leading authority on hum in this forum.

**Azeke** · 04 December 2005, 00:30 Sunday

Thank you Bigburner, I couldn't remember.

Best regards,

Azeke

**SteveL** · 05 December 2005, 19:52 Monday

Update: RCA cables made the noise *worse*. Working on grounding the chasis' to each other...

**ThomasW** · 05 December 2005, 20:53 Monday

I have read BruceK is the leading authority on hum in this forum.

Ken Bruce is an electrical engineer.

Here's what I've done:
1. Bought a Ground Block from Radio Shack, wired a 10ga ground to my water pipe, and secured the ground wire to the pipe with a metal hose clamp. Noise still there.

Most electrical codes don't allow water pipes as an approved ground. That's why ground rods were invented and why every electrical panel is bonded to a rod per code. By grounding to the water pipe you created a second ground point, and created an instant ground loop where you had none before.

5. Used the ground-lift setting on my amps - noise still there.

Ground lifts aren't as effective as using a cheater plug.

It really sounds like a defective piece of gear.

Which Furman device are you using?

As a diagnostic tool put a cheater on every device. If the hum goes away then slowly remove them until the hum returns. That will tell you the source of the problem if it's a ground loop.

Despite the hype and hysteria using cheaters is not a significant threat to life and limb.

The use of a cheater becomes problematic if ALL the following occur simultaneously.

1)You have a piece of equipment where somehow the +120VAC comes loose from it's connection in the power supply, and contacts the chassis.
2)The circuit breaker then fails to pop
3)You touch the chassis and for some inexplicable reason aren't able to release your grip.

Your chances of getting hit by lightning are significantly higher than being injured by the use of a cheater.

**SteveL** · 05 December 2005, 21:52 Monday

Furman PM-PRO II

Page not found

http://www.partsexpress.com/pe/pshowdetl.cfm?&DID=7&Partnumber=248-753

And re: grounding to the waterpipe -- my house ground is about 90-feet from where my satellite dish and cabling is - how would you suggest I run a ground? Just throw down some Romex to the ground source?

Not afraid to use a cheater - I'm aware that it's mostly "alarmist" types that rant about how dangerous they are. But my CA-18 has a 30A plug, so I can't really attach a cheater to it too easily, and it's the piece that I've been using the ground lift switch for.

**ht_addict** · 05 December 2005, 22:25 Monday

Try running your sat coax from the wall to the power conditioner then too the sat box then to your tv and see what happens.

**SteveL** · 06 December 2005, 19:40 Tuesday

No coax connections on the power conditioner - it's strictly an AC conditioner.

**Stoney** · 06 December 2005, 20:39 Tuesday

Each wall outlet has the mounting frame of the plug connected to the house ground. Or, if one of your pieces of equipment uses a three prong plug, the chassis of that piece of equipment could be used as a common house gound point.

**ricktsu** · 07 December 2005, 03:53 Wednesday

Hello all ,

This is my 1st post. I joined mainly for Club Rotel where some of my equipment is and some of my upgrades in the next couple of months are going.

Anyhooo,

I thought I had the same problem w/ my Rotel amp. Do not know if this was suggested by try cheater plugs on other devices plugged in. My problem was my Panasonic Ae 900. Maybe the problem lies in one device that was normally not a problem.

**Snap** · 07 December 2005, 09:01 Wednesday

Originally posted by SteveL

I've got the worst ground-loop noise thanks to my DishTV HD receiver... and I've tried almost everything I can to fix it. I'm *confident* it's from the Dish Receiver - as soon as I unplug the coax, the noise goes completely away.

With every thing else on this thread that was mentioned.....Have you called Dish and told them that they sold you a bad Receiver? You have used all that equipment, and cheater plugs....you might want to call dish and let them know that your stuff is broke. The worst case....you get a new receiver and the problem is still there. At least then you can have some piece of mind that it is not the box.

You mentioned the ground to your Sat Dish. Running the ground from the dish to the house ground might not be a bad idea either. Just dig a small trench from the dish to the house ground and cover it up.

Let us know what you finaly find out.

**SteveL** · 07 December 2005, 20:38 Wednesday

Originally posted by Snap

You mentioned the ground to your Sat Dish. Running the ground from the dish to the house ground might not be a bad idea either. Just dig a small trench from the dish to the house ground and cover it up.

Let us know what you finaly find out.

Huge problem here -- the dish is on one side of the house, more than 90 feet from the house ground. And, NW AR is like one big flat rock, so you don't dig much of anything - you chisel.

I'll call Dish and see what they say.

**Sim reality** · 08 December 2005, 18:42 Thursday

I have a question:

Coax is cheap and the outer shell should be ground if they wired it correctly... Why not ground the outer shell of the Coax to the same ground as your HT?

**ToddAnisman** · 10 December 2005, 00:57 Saturday

Couple things to add....

A) Do you have a hum or Buzz? the distinction is important. some of the people here have been describing buzz; if you attach a line grounding one chassis to another and the noise disappears, that is an indication of buzz.

Buzz is a lack of ground reference, hum is caused by voltage within your ground.

B) There are two grounds- Power and signal; never mess with your power ground. If you are having issues w/ ground loops, the best way to deal with them is to break them; transformer isolation is the best way to do this.

this product works well...

Home

http://www.ebtechaudio.com/he-2des.html

Step on it!

C) Signal grounding is key; however it is tied into your power grounding. however, your dish is not the issue; it's floating. More likely there is a connection occuring across your multiple room setup, which is causing a ground potential to occur; the only way to defeat this is by breaking the loop.

Hope this helps

-Todd A.

**gcmarshall** · 10 December 2005, 23:02 Saturday

does this help at all?

Ground loop problems and how to get rid of them

http://www.epanorama.net/documents/groundloop/

Ground loop problem solving pages which tell how to get rid of those annoying humming problems in your AV system

**bigburner** · 11 December 2005, 02:59 Sunday

Originally posted by gcmarshall

does this help at all?

http://www.epanorama.net/documents/groundloop/

Many thanks gcmarshall, that's a great link.

I really enjoyed this quote from the article:

Usually ground loops are an after-the-fact type of problem in which the end-user blames the installer, the installer blames the manufacturer, and actually nobody is at fault. Neither the manufacturer nor the installer can usually predict where a loop will occur. Only after the system is installed can it be determined if a problem will exist.

**SteveL** · 13 December 2005, 23:52 Tuesday

Ok - I fixed the ground loop noise! Now, to see if what I did is extremely dangerous or not...

I took my ground block ($2.49 RadioShack), and instead of running the ground wire to the water pipe, I ran it to a junction box and tied it in to the ground wire. The ground wire that I tied it into is the same ground that feeds my A/V equipment. Connections are all very good (copper ferrule crimp to 120V ground, and is 10-ga Romex in conduit to the junction box).

Any worries with this set-up? It completely eliminated the noise, which was both a hum and a buzz (60Hz + higher frequency).

Thanks again for the advice/help/suggestions from everyone - they're all much appreciated.

**ToddAnisman** · 14 December 2005, 02:24 Wednesday

looks solid to me. Often times a water pipe isn't the greatest grounding rod....

what you've essentially done is eliminated the potential.

-Todd A.

**Stoney** · 14 December 2005, 13:48 Wednesday

My only concern is that you make sure you tied it to the ground (green or bare copper wire) and not the neutral wire (I don't remember if it is the white or the black).

**SteveL** · 16 December 2005, 19:48 Friday

Definitely tied to the bare copper ground wire; and white is neutral (in the USA) (didn't use the white wire - just the ground).

Thanks again everyone!

Nasty Ground Loop - tried everything