Earth/grounding loop?

  • Thread starter Thread starter DJ Strutt
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DJ Strutt

New member
Hey.

I have some kind of Earthing loop I think.....which creates quite a loud humming noise. Ive traced the main souce to be my DJ mixer which is plugged into my mixing desk.

I could solve it by un-earthing the DJ mixer....but thats a bit dangerous.

Any other ideas?

Thanks
 
How is the audio patched? Balanced or unbalanced? You could try putting a ground lift on the audio lines. Most direct boxs have this feature.
 
Thansk mate.

I think all my wiring is unbalanced. What does a ground lift mean? And i dont think i have a direct box either...not sure what it is either lol.

Thanks
 
Direct boxs have a few uses, the primary one being transforming a high impedence line level signal from something (like the line output on a bass amplifier) and converting it to a balanced low impedence line. A ground lift is a feature they generally build into a direct box for battling the very problem you're describing. It "lifts" the ground on the audio lines to help eliminate ground loops. Something else yuo'll want to do if you already haven't is to make sure all your equipment is plugged into the same electrical outlet so you'll have in essence a "star" grounding scheme. If you have gear pugged into multiple outlets around a room and then link them all together when you make your audio connections, you're setting yourself up for ground loop problems.:D
 
Thanks mate...

Ive done exactly what uve described :D I have 4 * 4 ways coming out of various plug sockets around my room, would one huge extension plug from one socket be better? Cos i would of thought that could cause fires etc ??

I dont really need a DI box because i dont have any intruments to play :p just my sampler and keyboard. Is there another way to create a ground lift?

Cheers.
 
Unless you're pulling a lot of current (like from a 5 or 6 big power amps) a single power strip should work just fine. Make sure you get one with a circuit breaker on it and you should be covered. If you're just running line level stuff like your mixers, effects devices and your monitoring system, you should be fine.
 
I have about 15 pieces of equipment....and ive never seen a 15 way power strip lol. damm:rolleyes:

Anyone else got any ideas about my humming noise?
 
You could plug 3 power strips into your 1 power strip.

That would give you 21 outlets: 6+6+6+3.

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I have another question for you.

How do you have your DJ mixer setup?

Do you have some thing other that your turntables running into the DJ mixer?

Are the grounds on your turntables connected?

Are the grounds on your turntables working properly?

Do you need them replaced?

We know it has to be something about the mixer or the connections to the mixer.

So, let's get this figured out for you. :D

spin
 
Well...both my turntables seem well and trully earthed so im guessing thats not the problem. And when I plug my mixer into my amp direct there is no humming noise...

I know what the prob is....the fact that everything is grouded....creating a loop so that the excess voltage has no where to go.....grrrrrrr

I just dont know how to stop it! :confused:
 
I feel ya. I know it's frustrating, but I'm sure that it can get figured out.

good luck

spin
 
Disconnect everything from the mixer... except your amp/speakers. Keep volume off (so you don't damage your speakers), and one at a time, re-connect a device back onto your mixer. After each connection, check for the ground hum. When you add the device and hear the hum, you've found the unit that's giving you difficulty.

You can then start looking at ways to isolate it once you've discovered the actual unit. Could be a bad ground on the turntable, or a ground loop, or even simply a bad cable.

Long process to troubleshoot but there's really no other way....

Bruce
 
Thanks mate. Ive allready done that and located it to my DJ Mixer which plugged into my mixing desk. And all the connections are fine...and if I unplug my turntables from the DJ Mixer the hum is still there...so its not them.

Hmmmmm
 
So that means the issue is between your amp and mixer is nothing else is connected to your mixer.

One thing you can try is to put an isolation unit between your mixer and amp - Ebtech makes a 2 or 8 channel unit called the Hum Eliminator. This will isolate the line signal between the amp/mixer. If the problem is a ground loop via the audio line, then this will fix the problem, if not, then you'd have to look at the AC - and you could get an AC isolation unit, but they are expensive.

Also... before throwing money at the problem, check out these links :

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

http://www.securityaudio.com/groundloops.htm

http://www.rane.com/note110.html

Bruce
 
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