Ground loop issue

[jzoz01]

I've ripped my system apart and rewired twice now and just can't get rid of my ground loop hum. I tried connecting pieces one at a time and nothing, but as soon as I give up, it comes back. I'm getting kinda flustered. Anyone had any expirience with standalone ground loop issolators? I want somthing between my preamp and amps.

I'm about at the point where I might just ditch the NAD preamp and get something with XLR. This is driving me nuts....

[SCOOTERDOG]

I had the same problem about a month ago. It all started when I had my

new HD Receiver installed. I would only get the hum when I played DVD

Audio disc and for the life of me could not figure it out. I discovered

if I disconnected any of the video outs coming from the sat receiver

the hum would go away. I talked to Direct Tv and they sent me another

unit but it did the same thing. As I went wire by wire I dicovered that

the sat receiver was the only one with a ground plug and all of my

other components were of the 2 plug variety. I switched cables around,

bought new cables etc. I finally decided to just use a cheater plug

that takes a 3 prong plug to a 2 prong and my hum went away. I know the

pros and cons to doing this but in the end it all goes into a nice

power center with protection so I said what the hay. Have not thought

about it since.

Now if you have digital cable Jensen makes a ground loop Isolator that

sells for about 6o bucks and I hear it works great, to bad it won't

work on sat systems.

VRD-1FF Cable TV Ground Loop Isolator

Analog, Digital and Cable Modem Compatible

(Supercedes the Model VR-1FF)

**Note: This unit will NOT work with satellite systems**

• High Isolation Reduces Ground Loops
• 2MHz to 1300MHz Bandwidth
• Low VSWR Prevents Signal Degradation
• Low Insertion Loss for High S/N Ratio

go to http://www.jensen-transformers.com/

good luck!

Scooter

[westcott]

The usual culprit is the sub(s). Test these first by unplugging them then go from there.

Try a different circuit in the house or go straight to some form of signal isolation\filtering.

Also test the outlets and make sure they are properly grounded.

[jzoz01]

The only subs in the system are the Klipsch THX, but they run off of a single amp, which plugs into my power center. Every single pice of equipment is run through the power center (including the coax) and all have 3 prong outlets except for the dvd and tv.

[Guest BobG]

I assume your power center uses a 3 prong AC cord. If so, start by checking each component that uses a 3 prong AC cord. Temporarily use a 3 to 2 prong cheater plug (might need several to test mulitple components at once). Or use one TEMPORARILY on your power center. This should allow you to find the source of the ground loop. Remember, this is not a faulty component, but rather the combination that's the problem.

[travisc]

YOU DONT HAVE A DIMMER SWITCH IN THE CIRCUIT DO YOU?

[ajcllc]

I just had this problem a couple of days ago. It turned out to be that my cable wire was not grounded. I grounded it against a pipe in my basement, and now it's gone. (From what a read, I gather that the cable wire for the cable box is the culprit more often than not.)

It was suggested to buy one of these: Jensen Cable TV ground isolator, or if you want something cheaper that also does the trick or http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=180-075

Hope this helps.

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[jzoz01]

Currently I have my coax run through my power center as well (Monster HTPS-7000SS), I was under the impression that the power center took care of ground loops on the coax, but maybe it's just for surge protection. I'll pick up a issolator and a cheater plug and do some expirimenting. thanks for the info guys.

[SteelerFan]

If you've unplugged everything except the amp from the preamp and still have the hum and all else fails ( provided your amp has XLR inputs) then get yourself some RCA to XLR interconnects. I tried everything to cure mine and had resigned myself to just putting up with it when Russ gave that tip. Worked like a charm.[]

[33klfan]

I'm not sure about what is meant by a ground loop. Is the hum going through all the speakers or what? I have posted a problem with my nad t753 putting hum like noises through the surrounds. Maybe this is where i could find out more. It seems like nothing solves my problem, even though i didn't try everything, kind of just gave up, so i don't understand. Maybe this is the problem, i don't know, i would be mad if it was something small that could be easily fixed, unless it's just supposed to be an accepted background noise with the nad's. Maybe u guys can help. I know i didn't give much troubleshooting but i have more i think under my wining noise with nad's forum. Thanks

[DrWho]

Ground loops are seriously the biggest headache in audio. As BobG

mentioned, it's the combination of compenents so there's really no easy always works remedy.

Btw, going to XLR won't necessarily fix the problem...

[Guest BobG]

33KLFAN,

As a test, connect ONLY your NAD, a single source component (DVD player) and your speakers. No TV, no cable box, no nothing. Just that basic set of components. Do you still have hum / noise in the rears? If so, it's not a ground loop problem. Typically, problems in just the rear channels indicate other issues with the preamp/processor/ receiver.

If using this simple system eliminates the hum, then start adding one component at a time. When you add a component and the noise returns, it does not mean that the component you added last is the problem. Instead, the whole system combination creates ground loop noise (though it is odd that it would be in rear channels only). Be suspicious of any component that is connected to a TV antenna, TV cable or satellite dish system. Also, be suspicious of any components that have three prong AC cords. These are all sources of additional grounds and are likely to cause ground loop noise.

Do a search on this forum for "ground loop". You'll find lots of helpful info.

[jzoz01]

If you've unplugged everything except the amp from the preamp and still have the hum and all else fails ( provided your amp has XLR inputs) then get yourself some RCA to XLR interconnects. I tried everything to cure mine and had resigned myself to just putting up with it when Russ gave that tip. Worked like a charm.[]

I thought about it, but I guess I don't understand how it would help. XLR eliminates noise because it's a balanced connection. Using a RCA to XLR is still an unbalanced connection. Am I missing somthing?

Anyway, I chassis grounded my dvd player and it almost completely went away. Then..... I turned my sub on and it came back (although not as bad as before). The sub is a Klipsch THX Ultra 2 (KL-120 and matching amp), which has a 3-prong ground and runs into the samepowercenter (connon ground) as all other connected equipment. Any other ideas??

[michael hurd]

Run a small ground wire from the Klipsch sub amp to the rest of your equipment. You should have no problem locating a screw on the back of the amplifier to attach a small gauge wire with a fork terminal. This should alleviate any noise problem.

[SteelerFan]

If you've unplugged everything except the amp from the preamp and still have the hum and all else fails ( provided your amp has XLR inputs) then get yourself some RCA to XLR interconnects. I tried everything to cure mine and had resigned myself to just putting up with it when Russ gave that tip. Worked like a charm.[]

I thought about it, but I guess I don't understand how it would help. XLR eliminates noise because it's a balanced connection. Using a RCA to XLR is still an unbalanced connection. Am I missing somthing?

Anyway, I chassis grounded my dvd player and it almost completely went away. Then..... I turned my sub on and it came back (although not as bad as before). The sub is a Klipsch THX Ultra 2 (KL-120 and matching amp), which has a 3-prong ground and runs into the samepowercenter (connon ground) as all other connected equipment. Any other ideas??

Nope, you didn't miss anything. All I can say is it worked for me. Sounds like you may have a different issue and you have tracked it down.

Now as far as the sub...I used a cheater plug on mine and cured it's hum. However, the hum was through the sub only and not through the rest of the system.

[33klfan]

So, BobG, so unplug everything except for the speakers and dvd player from the receiver, and then try it? Boy, now if i think about it, when i first got my second nad t743, and this one still does the same thing, i tried hooking up the T743 with all the speaker wires out away from all the other ones that were crammed behind my equipment, and just hooked up the dvd player, and i remember it still doing the hum or i actually say more like a whining hiss or hum noise from the surrounds. I actually thought that the center did it to, but i eliminated that thought one day when i was troubleshooting. It's just the surrounds now. So i'm pretty sure the only cord that was still near like all the other cables in back of my equipment was the power cord for the dvd player. All of the speaker wires and optical cable, and nad power cable was free from any other cords. To me it sounds more like an issue like u were saying with the preamp/processor/receiver. I hope u can help more. Thanks.

[dragonfyr]

I hope you'll pardon me sticking my nose in here!

As soon as I saw the mention of XLR inputs, i decided to post this info in two parts.

Perhaps it will help, as it addresses the classic XLR "pin 1" controversy that has caused more headaches with anything balanced then any other issue i know!

I gues this my way of saying that I don't mind trying to be of help, but i don't have time to get my hands dirty![]

So I will post this in the hopes it helps..

Of course if it is not apropos....nevermind![]

PIN1.pdf

[dragonfyr]

Here's the other post...

HOPE it helps![]

Pin1Revisitedpdf.pdf

[Guest BobG]

If you still experience the noise with just the speakers, receiver and DVD player connected, it is not ground loop. What happens if you JUST connect rear speakers and the receiver (no source)? Do you still have noise in the rear channels? If so, it's coming from the receiver. I've seen cases where the receiver circuitry is sensitive to interference from radio stations causing noise in select channels. Perhaps you should try a different brand of receiver to eliminate this as the cause. Also, ground loop noise is 60 Hz hum (sometimes 120 Hz too). It's a very specific type of sound - a low raspy noise. If the sound you have is not that, then again, it is not ground loop and the cure is elsewhere.

[DrWho]

If you want to hear what a ground loop buzz sounds like, plug in a

cable to any input on the reciever. Then turn on the speakers and touch

the middle pin with your finger. If you don't get a very loud buzz then

your body is probably too well grounded. In which case, go ahead and

touch the middle pin to the metal frame on some other electronic device

that is powered on (a computer works great for this). You will end up

with a really nasty and loud buzz so be sure to keep the volume down.

Let me stress to be careful when doing this because it is very easy to

blow stuff up, but is the easiest way to familiarize yourself with the

ground loop hum/buzz.

It's really fun to do when you have a subwoofer system capable of

extreme volumes. I've done it a few times to scare the crap out of

curious ppl touching the speakers...one loud blast and they never come

back []