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Bad Interference / Noise in Amp!

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Postby EastCoast » July 5th, 2009, 9:51 am

I'm a guitar beginner with a new small amp (Peavy Vypyr). The amp worked fine at the music store. BUT!-- When I plug in an instrument cable at home, there's a major loud pulsing tone / noise / hum that comes out of the speaker (even if no instrument is connected).

I live in an area that I think has some pretty strong continuous radio transmitters and I suspect I may be hearing Rf interference from that.

Does anyone have any suggestions for troubleshooting? My instrument cables are OK, but not the highest quality. Maybe there is a strongly Rf-shielded cable I could try? Thanks.
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Postby kent_eh » July 5th, 2009, 10:44 am

It's not necessarily your amp.
All amps will buzz/hum when there is nothing plugged in. Or more correctly, if a cable is plugged in to the amp, but there is no instrument on the end of the cable.

When you plug in your guitar, and turn the guitar's volume knob down to zero, is the noise still there?

What kind of guitar do you have? What kind of pickups does it have?
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Postby Wes Inman » July 6th, 2009, 6:53 am

Yes, try the amp in different outlets around the house. Certain appliances like refridgerators and air conditioners can cause sounds like this, even a TV. My TV used to cause hum in my amp, I would turn the TV off and the hum would immediately go away. Flourescent lights especially cause noise and hum on guitar amps. You may find simply using a different outlet will eliminate the noise.

There's all sorts of things that can cause noise in amps, one day I was practicing and heard the Police talking through my amp. I looked out the window just as a Police cruiser was passing by. :D
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Postby MarkII » July 11th, 2009, 6:01 am

I am probably the least knowledgeable here when it comes to guitar amps but since this problem is close to what I just went through I thought I would comment. I purchased a new Peavey Vypyr 15 from GC after one day it starting sounding like the problems you are having. I called GC back and talked to them, they said this amp was having a lot of problems and gave me a 800 number to call to get my money back (I purchased a warranty plan). 99% of the time mine sounded just like yours, just a couple of times it was quite and sounded pretty good. After my replacement check came I took it back to the store and for a few more bucks purchased a nice used Marshall MG30. This may or may not be your problem but it sounded similar. Good luck I hope you solve the problem.

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Postby Blue Jay » July 11th, 2009, 11:14 am

Not a bad, caring crowd for a first post?

There's probably no ONE answer till you go plug the amp in somewhere else (again) - easy to do, and/or bring another amp to the house and see what it does under the same conditions. That would involve a little more work, but may be worth it.
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Postby bloos66 » July 11th, 2009, 5:00 pm

I've found that after moving houses recently, the hum (and interference) from my guitar/amp has gotten A LOT worse. It's really quite annoying. The thing is that this house is very old, and we also have a fairly large port facility nearby with large ships docking every day. My tube amps are definitely a lot worse than the SS one (Roland Cube).

As other people said, there's not an easy answer to your problem, some experimentation will help, perhaps borrow another amp from a friend and see how that goes. Good luck!
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