laptop with mains power produces ground loop

dave_house · Post by **dave_house** » Tue Jan 30, 2007 5:44 pm

I have a laptop running live, connected to an Edirol UA-25. This is connected to a preamp mixer which is connected to Genelec 8020A monitor speakers. I had a ground loop problem between the mixer and the speakers which I solved with a ground loop isolator.

Now, when the laptop is running off the battery, all good. When its running off the mains, nasty whiny hissy buzz. Anyone else have this problem? My 1st thought was to get another ground loop isolator, but where would I connect it? The laptop is connected to the UA-25 via USB so an isolator is no good there!

any thoughts?

Cheers, Dave

martin808 · Post by **martin808** » Tue Jan 30, 2007 5:54 pm

To fix this you can cut the earth off your plug. or get a small extension lead and cut the earth off that to save cutting off your moulded plug.

some people say its dangerous but i've had mine like this for 2 years, works a treat and never had a shock...yet

moscom_musik · Post by **moscom_musik** » Tue Jan 30, 2007 6:05 pm

I had the same problem with mine and the fix Martin808 suggests you is a good solution.

dave_house · Post by **dave_house** » Tue Jan 30, 2007 6:25 pm

cool, cheers. Forgive my ignorance, but whats the potential danger of an ungrounded plug?

vinkalmann · Post by **vinkalmann** » Tue Jan 30, 2007 6:27 pm

DO NOT cut your plug! Get a ground lift adapter. It's one of those plugs that goes from a three prong to a two prong. You can get them for nothing at a hardware store.

Tommy Bruise · Post by **Tommy Bruise** » Tue Jan 30, 2007 6:32 pm

or a ground loop isolator if your in uk from maplin

£9

DO NOT cut your plug

martin808 · Post by **martin808** » Tue Jan 30, 2007 6:34 pm

I cant see what the danger is. I know loads of people that have done this. as i said mine has been fine for the past 2 years.

cut the earth!

Tone Deft · Post by **Tone Deft** » Tue Jan 30, 2007 6:44 pm

The only danger is that if the modified device gets a short in it (like a beer gets spilled all over it) and the electricity runs amuck it won't have that GFP (ground fault protection) wire to run down and into the ground, it'll try to go through you, or the table, or whatever other path it has to resort to to get to the ground. It's a safety thing that really very rarely ever comes into play, it's to keep you from getting shocked in case of a catastrophic failure.

The buzz is probably coming from the laptop's power supply, the battery produces DC voltage that the computer runs off of, the power supply takes AC and makes DC, this can be a noisy process. Maybe buying a different one could help.

Just play LOUD

martin808 · Post by **martin808** » Tue Jan 30, 2007 6:46 pm

I understand that in most appliances but on my laptop adaptor it has 3 pins going into the adaptor and only 2 come out to plug into the laptop,

Tone Deft · Post by **Tone Deft** » Tue Jan 30, 2007 6:51 pm

martin808 wrote:I understand that in most appliances but on my laptop adaptor it has 3 pins going into the adaptor and only 2 come out to plug into the laptop,

by adaptor you mean the 'brick' power supply? The plastic box in built into the power cord? That's because the 3 prong side is AC (input), the 2 prong side is DC (output). DC doesn't need 3 prongs because 1 of those prongs IS a ground, AC has Line, Neutral and Ground (GFP).

martin808 · Post by **martin808** » Tue Jan 30, 2007 7:06 pm

get you now. still, it works. just be careful with the beer.

dave_house · Post by **dave_house** » Tue Jan 30, 2007 8:01 pm

recon i'll look into those ground loop adaptor thingies. Simply cos im a notorious clutz an dif anyone was gonna spill beer over their kit and fry it/themselves, it'd be me!

cheers for the thoughts people

subterFUSE · Post by **subterFUSE** » Tue Jan 30, 2007 8:17 pm

This is a common problem with laptop computers.

It is solved by purchasing a Ground Loop Isolator.

The problem is so common, that Ableton should include an isolator in the damned box with the Live software.

martin808 · Post by **martin808** » Tue Jan 30, 2007 8:29 pm

about a year ago, I was playing a gig and some drunk chick came over and spilled a glass of vodka and coke all over my laptop. In my panic i grabbed a cloth and started wiping it off.
I never got a shock but i did press the power button by mistake which was stupidly set to shut down when pressed.
luckily i was playing back to back with my mate and he managed to keep it going till it was booted back up again. A lucky escape I think.

simplesatisfaction · Post by **simplesatisfaction** » Tue Jan 30, 2007 8:30 pm

Solution:

Or - if you use a direct box - the ground lift switch will often solve the issue.