Ground loop problem?

[DeeRusche]

Hey ladies and gents,

so I'm thinking I have a ground loop problem via my Minibrute.

I'll say first that only these three things are plugged in and I'm using headphones only (though noise still present when through speakers). My set up is Windows vista laptop connected via usb to Behringer Xenyx Q1202USB mixer and Minibrute connected via USB. I have a slight but high whine coming out from the mixer from the minibrute channel when turned up (in fact even when volume of minibrute is turned to 0). If I go direct into the brute with phones I don't get it... or if I disconnect the brute usb to the computer and listen to brute direct via the mixer. Unfortunately I can't remove the laptop power as the battery is broken and would die. All the power leads are double insulated and I have tried them in one power socket and also coming from two sockets in various formations.

If I have the laptop and mixer or mixer and brute on it's own no whine so I'm not sure how or where to break the problem in a simple manner. Could it also be a problem with my Asio connection, usb connections or is it the brute itself connecting the loop? Is it a case of computer can't handle the two usbs somehow?

Annoying me and already losing a few days work over this. Cheers for any help, first timer on here.

[DeeRusche]

One thing I have just slightly fixed is that when I put the minibrute through my rack units of EQ, comp and FX the whine goes away... thought it would still be present. This half solves a problem but why am I getting it still with only the three of laptop, mixer and brute.

I've got them set up on my mixer on channel 1+2 and the one channel going through extras produces nothing but the simpler way has whine still.

Still need to solve this as when I'm writing or travelling I still want to demo in the simple set-up.

[Terrym]

Hi ,is the noise you hear a whine or a hum ? as hum suggest its a earth loop  around 50/60 hz . not sure what it could be if its a whine unless you have feedback . if a hum you need to lift the earth from the mixer to the brute. in the past i tried just putting a bit of tape round the bottom ring of the jack plug to se where the hum is coming from .but its not the pro way of dealing with earth loops.

hope this help

terrym

[DeeRusche]

It's definitely above 1khz but the reason I'm thinking it's a loop is because disconnecting one of the usb's seems to lift it. It's just weird because brute and mixer on it's own is fine. Laptop and mixer on it's own is fine. I should explain that the Behringer mixer is acting as my soundcard as well as my internal laptop sound is broken.

I've recorded it for you. The left side of you head is via my rack units direct out from the main out of the minibrute. When pushing the gain it's got some noise but nothing to bother me. The right side is direct from phones out on minibrute to the desk. You'll hear the whine and also the difference when I disconnect the minibrute usb from laptop and play the same notes in the right. Then it's whine free but I obviously need to connect the brute.

I should say whether it's main out or phones out makes no difference, I've eliminated that. Direct to mixer in anyway still gives me this whine.

[Terrym]

Ok had a listen to your mp3 this sounds like its coming from your computer if it only happens when the usb is plugged in .sounds like a digital signal .the reason it may not be there or quitter when going through other equipment maybe due to the other equipment having a filter for noise or earth lift built into the circuit . as i said before try isolating the earth on the lead leaving the brute. see if that get rid of the problem.


hope this helps

terrym

[Terrym]

Ok had a listen to your mp3 this sounds like its coming from your computer if it only happens when the usb is plugged in .sounds like a digital signal .the reason it may not be there or quitter when going through other equipment maybe due to the other equipment having a filter for noise or earth lift built into the circuit . as i said before try isolating the earth on the lead leaving the brute. see if that get rid of the problem.


hope this helps

terrym


Just a quick update .try buying or using a usb lead which has a filter on it .these normally look like round bits connected near to one end of the lead .they cut out upstream data that is bleeding over.