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I was running sounds out of the box into a guitar amp through an interface and my laptop was running low on battery power, so I plugged it. I got this noise after plugging it in and I couldn't figure out how to get it to go away and still be able to do what I was doing.

It's happened before. Before, I was using the headphone output on my laptop and this time the headphone out on my interface. In both instances I was using my guitar amp (different input on the amp, but I don't think it makes a difference since I'm getting the same sound). Before though, the noise would randomly[it seemed] go away and everything would be fine. I've tried a lot of things (unplugging things, twisting/nudging cables, switching the ends of the cables around, moving things closer or away from other things) but nothing remedied the situation.

The noise goes away when:
-I unplug my laptop
-or unplug the usb connection between my interface and laptop.

And it seems to change in response to computer activity like clicking on things, moving over icons, etc.
I recorded it with my zoom h2 incase that helps identify what it is or if any of you have experienced this kind of noise.
Soundcloud

I was contemplating recording a sample pack to share, but I'll have to wait for my laptop to charge

I think it's possible some kind of grounding problem, not totally sure.

I also think there is some box thingy, that I seen aimed at Laptop Dj's to stop this.

I can't remember, anymore about


This guy knows what is up

You could look into a power conditioner or possibly a ground loop interrupter (which is likely what's in the video 3za posted).

Have you tried different cables?

Also, I think the amp I use is pretty old, and it also has this sound, so it may be that.

Try plugging the amp into a different outlet from the laptop.

Yes I tried different cables and I have a Line 6 amp, so I don't think those are an issue.
I had them plugged into different outlets to begin with as well.

I indeed have the 3 pin connector like he mentioned in that video!
I ordered that Behringer HD400 that he used.
Also I read about using a ground lift adapter (3 prong to 2 prong)
http://en.wikipedia.org/wiki/Cheater_plug
"Cheater plugs are also used to break ground loops in audio systems.[4] This practice has been condemned as disregarding electrical safety.[4][5] An alternative is to use an isolation transformer made specifically for this purpose."
Apparently the HD400 uses the transformer method.

I don't know how your plugs work over in Freedom-land, but usually across the pond you can get away with just removing the ground connection or 'lifting the ground' as the term mentioned above. That is 100% a ground loop problem that you have there though.
Are you using a balanced cable to connect from your interface to the amp?

It's definitely possible but it seems to be discouraged for safety reasons. My friend told me it's not really a big deal unless you're outside in the rain or some shit. He lives in an old house with old wiring and 2 prong outlets and uses the ground lift adapters with power strips all the time. I ordered a 2 pack of those adapters with the HD400 so I'll see how it compares when it gets here!
I think the previous owner of my other guitar amp removed the third/ground prong lol I've not experienced any problems with it, so I guess it's not that big of a concern?

I believe I'm using an unbalanced cable. It's just a standard guitar/instrument cable.

Its whats called a "ground loop" its where the shared ground picks up noise from a power supply.
You need something that will replace the ground signal with a new, clean one like
this (with jack in/out) or a DI box with a ground lift button (but thats normally XLR outs)

I have done the earth pin removal before, but it only becomes really dangerous when something goes wrong as i personally found last week when i plugged in a dodgy (i didnt know that it was) compressor and it actually made all of the metal units plugged together live and suddenly i was literally wobbling with electricity, whatever i touched.

^On this package of ground lift adapters I got, it says they are grounded. I read somewhere that the metal piece on the bottom of these works as a ground, so these plugs would be a safer alternative to removing the pin.

Ok, so my HD400 came in today and I tried it out. It works pretty well. I tried a ground lift adapter and it reduced the noise volume wise about the same. The tone of the noise was different though. When I turned the master volume on my amp all the way up with the ground lift, I had less of the sound I posted above and more of the 60Hz Mains hum sound like when you unplug a guitar from an amp and touch the end of the cable. With the HD400, it was still that gritty and high tone. Both of them reduced the noise significantly though, so problem solved. Perhaps when you turn anything up all the way(especially guitar amps), you're bound to get some noise?

Of course I tried using both simultaneously[I thought maybe it would double the noise reduction lol) and it made things worse.
I actually had to use the HD400 going out and back into my interface when I was recording. I'll record some usable stuff tomorrow and share it with you guys.