I bought this ground loop eliminator and put it on my laptop power supply:
Amazon.com: Ebtech Hum X Voltage Hum Filter: Musical Instruments

It doesn't change anything at all. Do I need something between my guitar and my Mbox? I noticed that if I unplug my computer, it is still there. Much quieter, but still there.

I resorted to taking off my shoe and sock so I can put my foot on top of the Mbox while I record. There has to be a better way.

What you have is an obvious ground loop.

You could try using a direct box with a ground lift between the guitar and the mbox mini.

Well, as far as I know, this could be one reason a firewire interface is superior to a USB interface.

For future reference consider getting a firewire interface instead.

Firewire uses an isolation transformer and thereby eliminates any chance for interference and hum.

http://en.wikipedia.org/wiki/IEEE_1394_interface

The "ground loop eliminator" is essentially a ground lift. What kind of pickup system or transducer are you using in the guitar? This kind of hum isn't particularly unusual in some of the cheaper peizo transducers out there. It's sounds like 60 cycle hum to me. Very similar to what you would find with a single coil pickup on a Stratocaster. You might find that using a proper acoustic guitar preamp will eliminate the hum.

hueseph wrote: You might find that using a proper acoustic guitar preamp will eliminate the hum.

Yup, Hueseph, your right. A humbucking pickup may be the answer, although I have to say I like the sound of a mic on an acoustic.

Have you tried a mic for your sound?

I just have to say that placing your bare foot or any other body part on any electric device in order to eliminate hum is a very dangerous practice. If the device has hum from improper or inadequate grounding you are offereing yourself as a potential ground, if there is/ were/ will be any greater problem the way you will find out about it will not be pleasant and might be fatal. Really try and use some common sense.

Ok definitely what jg said here!

I've tried a ground loop eliminator, a DI box with ground lift and a power conditioner. None of them did anything to the buzz. The only thing that works is to unplug the laptop and run off batteries while recording. I didn't used to have to do that.

damajackal wrote: I resorted to taking off my shoe and sock so I can put my foot on top of the Mbox while I record. There has to be a better way.

LMAO

Ah the magical black art of recording...
The cat is out of the bag now!
There are NO secrets left anymore!

If putting your foot onto the box stopped the buzz, are you 100% sure it was electrical and not a mechanical problem? Good for a foot massage.

I wouldn't've thought the skin was conductive enough to act as a sufficient ground. But what do I know.

damajackal wrote: Hey everyone! I've got a problem and it seems so basic, but I can't solve it. I'm using Pro Tools to record my acoustic guitar. I have an mbox mini as a USB interface. When I plug the guitar into the MBox, I get this low ringing, electronic sounding buzz.

I had the problem before and solved it with a grounding plug added to my computer's power cable, but now, even that isn't working. The only solution is to unplug my computer and run on batteries while I'm recording acoustic guitar. That's not very practical though. The buzz goes away if I touch the 1/4" jack with my fingers, but obviously, that's not practical at all. I'm no electrician, but I think that means I need the power to be grounded, right? I'm already using a grounding plug and it's not helping.

I plugged in my microphone and nothing was wrong.

Here's a sample of it. You can hear the buzz before I start playing my crappy chords:
http://www.rhunekincaid.com/buzz_sample.wav

In all seriousness though....what I'm hearing kinda sounds like typical guitar hum/buzz. The guitar itself is really clean sounding beyond that low hum in your recording. Have you tried a different instrument cable?
Is this an acoustic guitar with a battery powered preamp?
Maybe check that. Check all your jacks on the guitar and M-Box.
Make sure your not sitting near something electrical that is getting picked up from the guitar pickup.
Turn off anything wireless on your computer so it's not transmitting. Move you cell phone to another room and make sure nothing like that is in the room with you causing some interference.
I don't think this is poor grounding, sounds like it might be something with the guitar.
Have you tried any other instruments (like another guitar) besides the mic into the input?
Need to eliminate each of the variables one thing at a time and make note of what is working properly and what doesn't.
I would start with using a space where there is no other electrical items operating other than your computer, interface and instruments and have all of your stuff plugged into a good surge strip plugged into a good grounded wall outlet.
Check using something you know works with the PT and interface to start (like the mic or another instrument) make sure that works clean and then go from there....when it starts to buzz then you'll know what the source of the noise is....
If you can't get the computer and interface to work clean with something then there's more than likely a problem with your computer or the interface.
Then you will need to try a different computer or a different interface...

As I was saying, this is probably just 60 cycle hum. Pickups usually have a ground wire soldered to the bridge somewhere giving you a contact that helps to minimize the noise while your hands are touching the strings. The peizo transducer you have probably has two conductor wiring. Ground is wired to the negative return on the Jack. That is why the noise lessens when you touch the input jack. I could think of ways to minimize the problem but none that wouldn't be a Mickey mouse solution.

Incidentally itsnot unusual to get noise when the laptop is plugged into the wall.

damajackal wrote: I've tried a ground loop eliminator, a DI box with ground lift and a power conditioner. None of them did anything to the buzz. The only thing that works is to unplug the laptop and run off batteries while recording. I didn't used to have to do that.

The problem is with the adapter on the computer...it has nothing to do with the guitar.

Space wrote: [quote=damajackal]I've tried a ground loop eliminator, a DI box with ground lift and a power conditioner. None of them did anything to the buzz. The only thing that works is to unplug the laptop and run off batteries while recording. I didn't used to have to do that.

The problem is with the adapter on the computer...it has nothing to do with the guitar.

Is there a solution for that?

damajackal wrote: Is there a solution for that?

The problem is that the battery charger only has a two prong cord. No ground. You can't safely add a ground cable to it.

Do you have another plug-in adapter for your laptop you could try?

You could also try getting a EMI ferrite choke and run the wire of the adapter through it to the laptop....?
They use those to block noise from being picked up in wiring....there cheap and might be an easy fix...

http://www.radioshack.com/product/index.jsp?productId=2996360