Ground Loops - Eliminating System Hum and Buzz

[FriedFrod]

noise problem

Hi, im really hoping somebody can help me here.
I have looked in alot of places trying to find a solution to my problem.

In our current setup there is absolutely nothing wrong, no buzzes or noises... but as soon as we connected the computer to our mixer it caused a loud buzz on the system.

Connected to the PC is a data projector. I found that by lifting the ground from the PC and removing the VGA cable from the data projector eliminated the noise.
Now I have been wondering if it is safe to remove the ground from the data projector.

Today I unglugged the power on every amp we have and everything on the stage, and found the buzz still exists. It is obviously coming through on the ground, and I have no idea how I can get this fixed.

Please I hope some one can help

Thanks
Matt

 

[SWHouston]

Matt,
First of all, WELCOME to the site !

I'm not sure that I've had the exact problem you're having, but there's a couple things you might check.

First, read my #36 post here on this thread, there may be something in it, that will help, and I'm thinking about the Ground Verification of your Receptacles. Get a long piece of standard jacketed Wire (16/14/12 Ga) and connect one end to a KNOWN good ground. Cold water pipe under a sink, or the metal part of the building (commercial) and check EVERY Receptacle that you are using for your system for a solid ground (the round hole). Using the Ohms Scale, you should verify Zero the meter out by touching the two leads together WITH the long lead in place, and use that reading as an acceptable Zero when you move out to the Receptacles. You shouldn't get more than a 0.001 Ohms reading, when probing into the Ground pin. If it's open, then you need to re-run the Ground in some way. Good luck with that!

While you're at it, (hopefully with a Digital Meter) verify that the Hot wire for the receptacle is showing up on the smaller of the two blades, if not, they you've got Reversed Polarity, and it's easy enough to swap the wires on that Receptacle. Don't forget to change to the Voltage Scale for this one !

You're mentioning lots of components there, check each one for continuity of Ground, from the Case to the Round Pin of the Power Cord for that component. Some of those molded Plugs on those things are made real cheep, and it's easy to assume that they're ok, but, don't make that assumption, check each one, including the Computer, ALL !

Now, I don't know if you are using any Two (2) Wire Power Corded equipment, and if you are and it's relatively new, the Plug on them is Polarized, where there are two different sized Blades, and if that's the case, you can't reverse connect them. But, if there's an older piece in your setup, and it doesn't have a polarized plug on it, you might try turning the plug over in the receptacle, and then marking it with White Out or something, where you can ID the better placement.

Lastly, you might do a Pin to Pin on the interconnect Cable (s), some/most carry a ground in them. It doesn't matter which wire of a multiple wire cable that carry's the ground, as long as the individual wires have continuity end to end, and there's NO cross connections between them. That type cable is made cheaply too, don't trust them either.

Problems like you have are like Roaches, very hard to get rid of !

Hope this helps !

Have a good Day !

 

[MGailing]

Hey guys,

I, like many of you, suffer from a massive hum issue in my set up. This never occured before I moved into my new place. Heres the deal: upon hooking up my receiver and all other electrical components in the room, I plugged in my computer monitor (24" BenQ) last. It appears that plugging in this monitor in any outlet within the room causes the hum on all channels (at different volumes - but rises w/ volume increase). I can fix the problem by running an extension cable between the monitor and the closest outlet outside of the room which is, unfortunately, in the bathroom. As you can tell, this is not a plausible solution. The monitor cable is a three prong, but no other cable in this room is except for the APC power surge protector - (not even the receiver). Any ideas? Thanks a TON.

 

[SWHouston]

MG,

1. Try another Monitor.

2. Get two 3-prong Plugs, and a piece of jacketed wire, long enough to reach from your setup, to that plug in your Bathroom.
Connect the wire to the Ground Pin of each of the Plugs, and run this "jumper" from the plug in the Bathroom, to your Power Strip that you're using for your system, or the Receptacle which powers it.

Understood, #2 is no better answer to your problem, than the Extension Cord, but, if it suppresses the hum, probably means that you have a Ground Wire interruption in your (House) system, and may proceed to repair that situation as necessary.

Hope this helps !

Have a good Day !

 

[WarrenS]

Two ground loop problems?

Ive got hum which appears to originate at a Parasound A/V processor. The hum occurs even with the power on the processor off, and whether or not the interconnect to the amp is one that is run through the walls/ceiling or one I run straight accross the room. It occurs through all of the amp inputs and processor outputs in approximatey equal volume and it occurs whether or not there are any inputs to the processer. Unplugging the processor eliminates 95% of the hum (maybe the residual 5% is my imagination after listening to it for a few weeks!)

The processor is in a cabinet on one end of the room, with a DirecTV HD/DVR box and a Sony DVD player, all connected to a Belkin surge protector. The amp is in a closet on the opposite side of the room (no surge protection right now), connected through the ceilings/walls to Solus inwall/ceiling speakers in their typical configuration. The amp is closer to the TV and front speakers, but on a different circuit. Unplugging the TV or DVD player makes no difference.

Unplugging the DirectTV HD/DVR lowers the volume slightly and changes the frequency slightly (or eliminates one of multiple frequencies) but most of the hum remains.

BTW the processor power cord is three prong, DVD and HD are two prong.

From what Ive read this sounds like one or more ground loop problems, but I dont want to spend the money on inappropriate fixes.

What is used to eliminate the A/V processor related hum? What is used to eliminate the HD box hum, (assuming that is needed in addition to anything used for the processor)? Assuming an isolator is correct for the HD hum where is the isolator connected? There are two outboard BB band converters connected between the dish and the box input. Does the isolator go between the box and the converter, between the converter and the cable from the dish, or does it not matter?

Apolgies if these have already been answered previously, skimming through the thread nothing stuck out as a specific answer to this combination of problems.

Thanks
WPS

 

[mtrycrafts]

Unplugging the DirectTV HD/DVR lowers the volume slightly and changes the frequency slightly (or eliminates one of multiple frequencies) but most of the hum remains.

Thanks
WPS

Do you mean unplugging the power or the antenna wire itself. Cable TV of any kind is the culprit most of the time when attached to the audio system in any way, even though the antenna leads.

 

[WarrenS]

Two ground loop problems?

sorry duplicate post

 

[WarrenS]

Good point

Do you mean unplugging the power or the antenna wire itself. Cable TV of any kind is the culprit most of the time when attached to the audio system in any way, even though the antenna leads.

I meant power. After your response I checked and disconnecting the antenna leads makes no difference, and I still go the slight reduction from unplugging the power.

I guess that elminates the cable isolator solution for that portion of the hum?

 

[FLASHMSTRC]

Subwoofer Causing Hum

Ok so I had some humming occurring after installing my Onkyo HT-SR800 HTIB. Isolated the problem to my subwoofer to the point where unplugging the subwoofer eliminated the humming.

As I turn the subwoofer up from min to max, the humming gets louder. I got a monster subwoofer cable to try that out, helped somewhat, but I still have the humming.

Searched through this thread and some others and couldn't find much on a subwoofer causing the hum. Anybody have any ideas?

 

[Johnd]

The subwoofer isn't causing the problem. The problem is simply manifested through the use of the sub.

Try a different cable, or unplug all other things on that circuit. That ought to solve your problem. Ultimately, a dedicated circuit (with dedicated ground) is the ultimate fix.

 

[FLASHMSTRC]

Excuse me for my ignorance on terminology, but when you say unplug all other things on that circuit, do you mean plug the subwoofer by itself on one outlet and everything else on a separate outlet?

 

[Johnd]

Circuit. Meaning anything between the circuit breaker and neutral bar...the only thing that should be plugged in between those points is the sub. Then see if you still have the hum.

 

[FLASHMSTRC]

Can you put this in terms of an electrical outlet? Does that mean plug the sub and the sub only into the outlet without using a surge protector?

 

[Johnd]

Let me put it this way:

Unplug everything but your sub, and then see if you still have the hum. It (ground loop) has to do with all the outlets that may be on that circuit, not just all of the things plugged into that outlet.

 

[SWHouston]

FLASHMSTRC,

Common Ground:
Try running a separate ground wire, between your Woofer and the other components of your system. ALL components should have a common ground created between them.

Reversed Polarity:
Try turning the Power Supply Cord/Box over in the Electrical Outlet, therefore reversing the polarity to it. This will not be possible, if you have a 3-Wire Power Cord, or if your 2-Wire Power Cord is Polarized (one blade larger than the other).

Equipment:
There's an inexpensive "checker" you can purchase (<$10) called a "Polarity and Ground Checker", which you can use to identify those problems in your overall electrical system in your house. Humming can be caused by an ancillary situation of poor/nonexistent ground or reversed polarity, at some other point in your house system. Might try that too.

Informtion:
You might try reading this, if you haven't already found it:
http://www.audioholics.com/education/cables/thinking-in-isolation-2013-a-primer-on-ground-loops

Best of luck,
Have a good Day !

 

[Johnd]

Try running a separate ground wire, between your Woofer and the other components of your system.

Informative post SW. As FLASH did not know what a "circuit" was, I was tentative about elaborating on the specifics of electrical wiring.

One caveat: Running a ground wire should be done by a skilled electrician only. Stray voltage may run through the ground, and we don't want any of our fellow 'holics buzzed. Ground wires need to be of sufficient gauge with appropriate clamping (and insulation, fasteners, and boxes) to be safe and NEC approved. The last thing anyone wants to do is run a wire (insulated or not) from ground prong to ground prong.

Otherwise, good info SW.

 

[FLASHMSTRC]

As I said in my post, excuse my ignorance on the terminology. I admit to have a basic knowledge, but no means the in-depth knowledge the both you have.

 

[Johnd]

Not at all. And I'll shy away from calling you ignorant. But if you disconnect everything but your sub, and you still have a hum, you have successfully narrowed your potential problems.

BTW: I have been following your ground issue in the tv thread. Hope it is easily fixed.

 

[FLASHMSTRC]

Like I said since installing a monster subwoofer cable the humming is almost 100% gone.

As for the ground issue with the TV, would you agree the ground isolator should fix things?

 

[dvroon]

How I Eliminated My Buzz

I tried unplugging everything with two or three prongs, one at a time. (The two prongers were unnecessary I found but I wanted to be sure). No joy. Then I unplugged the coaxial cable from the back of my Shaw HD box. The buzzing got worse. I plugged it back in. The volume knob didn't increase the buzzing, and when I turned my volume all the way down the buzzing was the only thing left. That meant it was downstream of my amp (from reading this and other threads). The only thing downstream other than my speakers was my TV! I unplugged that, voila, instant happiness. I then plugged in my TV without a ground, voila, no buzz on the amp and much cleaner HD picture.
I then used my handy GB GRT-500A tester and verified the hot and neutral lines were reversed in the plug behind my TV. I also tested the other plugs on that half of my house, and no others were reversed.
I am now going to shut off the breaker and reverse the polarity on the plug, so I can re-ground the TV, since that is far safer.
Thanks to this group, without your help I wouldn't have been able to diagnose and fix my problem. I hope my little scenario will help you diagnose yours too.