Ground Loop/Interference issue?

So nothing much has changed to cause this that I know of, apart from maybe the addition of a pair of Adam A5x (These were shipped with euro plugs, with UK adapters, I don't know whether this could be a factor)

Anyway to the issue, I'll explain my setup/signal flow so you have an idea

Imac (Mid 2011) > Akai EIE Pro (Ind outs to mixer) > Boss BX800

(There are other things in the chain, but with everything unplugged and moved away I still get noise)


So basically, If I run directly out the soundcard into the speakers, nothing, deadly silent and no issues.

If I go from the soundcard into the Boss mixer, wham, smacked in the face with a load of digital noise, mouse movements, whirring, all sorts. (I have tried plugging the mixer/soundcard into various sockets in the room, doesn't matter where they're plugged in, problem remains)

So I thought it could be the soundcard, but if I go from the soundcard to my Xone:22 mixer there is no noise, I also tested an old Behringer DX700 mixer, there is noise but no where near as much as with the Boss.

Now as the EIE Pro is powered, it can run without the computer on, so when I run a stereo out from the akai to the Boss mixer (with the computer off) there isn't any noise, then as soon as the computer is turned on, back to having noise again (You can hear the hard drive get up to speed)

I have also bypassed the soundcard and done a straight out of headphone to speakers, and fine, no noise.

So I'm slightly at a loss as to how to sort the issue, any help would be greatly appreciated.


If you want me to clarify anything just ask.

Is the laptop plugged in the same outlet as the speakers?

It's an imac not a laptop, and it doesn't matter if the speakers are plugged in or not,I get the noise basically when the soundcard goes in to the mixer but only when the comps on, as I've checked through headphones.

Ground loops happen when a device in the chain has more than one path to the main ground of the building. For example, if you have some sound equipment plugged into one outlet, and the rest to a different outlet, you are probably making a ground loop. Ideally, all sound gear should go to a single power outlet (obviously you can use power strips or whatever to "split" the power as needed to power your gear).

Macs are good computers, but more than one I've worked on as a tech have had grounding issues (which I found surprising). But the problem seems to be a combo of the iMac and the Boss mixer, so if moving everything to the same power outlet doesn't fix the problem, start checking the power connections on those components. Both have integrated power supplies, and both should have grounded (3-prong) cables, so if everything is correct, their ground connections should be going to the same source, and the ground loop issues should go away. If you've got a short or funky power supply in one of those components, though, you may need to have it repaired before your issues go away.

Quote:

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Originally Posted by DJTroyT

Ground loops happen when a device in the chain has more than one path to the main ground of the building. For example, if you have some sound equipment plugged into one outlet, and the rest to a different outlet, you are probably making a ground loop. Ideally, all sound gear should go to a single power outlet (obviously you can use power strips or whatever to "split" the power as needed to power your gear).

Macs are good computers, but more than one I've worked on as a tech have had grounding issues (which I found surprising). But the problem seems to be a combo of the iMac and the Boss mixer, so if moving everything to the same power outlet doesn't fix the problem, start checking the power connections on those components. Both have integrated power supplies, and both should have grounded (3-prong) cables, so if everything is correct, their ground connections should be going to the same source, and the ground loop issues should go away. If you've got a short or funky power supply in one of those components, though, you may need to have it repaired before your issues go away.

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Cheers for the help and info, I tried everything mentioned and no joy still got the noise, so I've gone ahead and ordered a new mixer so we'll see if the issue goes away, if not back to the drawing board.

http://www.gak.co.uk/en/behringer-hd...destroyer/1140

You could try this. A friend had a similar problem with a hum whenever he plugged his laptop in. No hum when not plugged in. I found this and it sorted the issue out. Might be worth a go, cheaper than a new mixer ��

luckily you have a pair of ground loop isolators in your kit for just such an occurence eh.

Yeah, also has the benefit of converting unbalanced output to balanced.

I've had my share of ground loop issues. The power cable on my last laptop was an issue. I used a power adaptor that removed the ground prong and that solved my problem. You can get one at the dollar store for about a buck. I would try that.

Cheers all for the advice, new mixer arrived yesterday, all is well, only time I have noise is when everything on max.

Anyway so I thought I'd carry on investigating anyway, so the issue is basically the connection from the imac to the soundcard, after several searches, it turns out it's the USB lead carrying the noise due to a bad ground. So, the solution, after much research there were a few posts suggesting to open up the USB lead and snip the black ground wire, and hey presto no noise from the computer, no more hearing the hard drive or anything.

So if you ever find yourself with a similar issue, give it a go, may not be the same for everyone but may be helpful for some.