Why is my guitar buzzing on my PC?

Question

I usually play my electric guitar through an amp simulator on my PC. It's helpful for recording as well as keeping the noise down in my apartment. I recently moved to a different apartment and am now having problems with humming/feedback. 

My guitar is connected to the desktop PC via a Line 6 Toneport USB interface. The buzzing occurs as soon as I connect the guitar to the interface with an instrument cable. Sometimes if I tilt the guitar around, I can eventually stop the buzzing by holding it in that specific position. 

I have another guitar and a bass, and both do the same thing as the first guitar. I've tried plugging the desktop PC into several different electrical outlets in the room, as well as different power strips. Nothing seems to alleviate the buzzing. I have a laptop, and I've found that if I connect one of the guitars to that, everything works just fine, no buzzing. I've recorded guitar for a couple years on my desktop at my old apartment with no problems. But now that I've moved here, I can't stop this annoying buzzing. 

Any thoughts? Just out of curiosity, I went back to my roommates' apartment and tried plugging my desktop back in. No buzzing.

Ken C · Accepted Answer

The fact that you can turn the guitar and bass and change the intensity of the buzz tells me that it's not being conducted down the power line.  Rather, it's being radiated from some source and getting into the pickups on your instruments.  Once that happens, there's not a whole lot you can do about it.

Since you've been able to take the same computer to another apartment and it works, it's likely not a problem with it, per se.

The first thing I would check is to see what the actual line voltage is at your place.  If it's very low (say, under 115 volts), then that could be part of your problem.  As the line voltage drops, computer power supplies draw more current to keep the power constant.  As the current draw goes up, the greater the chance for radiated interference from the supply.  

You can check this with an inexpensive digital multimeter (DMM) that you can get at Frys, Home Depot / Lowes, or Radio Shack.

While you're at one of these stores, spend $6 and get yourself an outlet tester.  You plug it in, and it tells you if the outlet is wired correctly and has a functioning ground.  No ground would cause these kinds of problems as well.

The fact that you can plug into a laptop and not have this problem really makes me think that your issue is low line voltage.

Are you in a different room when you plug into the laptop?  If so, go back to the same room as your desktop computer (and turn it off) and try it.  If there's not buzz, it's coming from your desktop, and probably for the reasons I said.  If it buzzes on the laptop in the same room, then the interference is coming from somewhere else.  Light dimmers, flourescant lamps, and neon are all big noise sources.

Good luck.

Greetings from Austin, TX
Ken

Anonymous · Answer

The PC should not be generating significant amounts of RF noise, with audio frequency harmonics. Check that your PC is properly shielded. Try tuning an AM radio to 1000 kHz (or just to one side of that if there is a local station broadcasting on that frequency) until you hear "hiss". Bring the radio closer to the PC (the hiss may get louder or change pitch) then "wiggle things" on the PC (keyboard, screen, power supply cables, communication cables, etc, to see if anything changes. If there are changes, focus on what you were doing when you heard the changes, to see if there is something radiating RFI.

Anonymous · Answer

It kind of sounds like your pickups are picking up some sort of electrical interference maybe you to close to your computer or you have something plugged in that is right next to where your guitar is siting. or maybe it could be bad wiring in your new apartment. its hard to say.

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Why is my guitar buzzing on my PC?

3 Answers