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Buzz Kill


strayGoat
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I'm experiencing a problem with hideous buzzing. Using an Orange Crush 20RT as a practice amp, w/ headphones. Clean channel. First with a Strat- and the noise is horrendous even in the bridge/mid position. Then the same problem with HBs. The noise basically disappears if the Tone is turned ALL the way down on the guitar, but who wants that? When I unplug the headphones, buzz gone.

 

Is my problem just crappy headphones? I'm using Yamaha 'phones that probably cost me about 20 bucks... Or is it a circuitry thing that's going to annoy the hell out of me no matter what headphones I'm using?

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hmmm interesting.... tried any other headphones? maybe even headphone jack out to computer speakers? I say always start with the cheap and simple stuff. Might even be some gunk build up in headphone jack. Hit with some contact cleaner (I use that all the time as I live near beach in Thailand and incredible how corrosion etc can impact electronics). Probably not the guitar... but then again, I recall sometimes have to use headphones if want to listen to radio as that cable acts as antenna... RF from hell? Have you moved amp around to see if that might impact picking up the squeal... good luck and if find out what the heck it is, share with us for future reference...

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hmmm interesting.... tried any other headphones? maybe even headphone jack out to computer speakers? I say always start with the cheap and simple stuff. Might even be some gunk build up in headphone jack. Hit with some contact cleaner (I use that all the time as I live near beach in Thailand and incredible how corrosion etc can impact electronics). Probably not the guitar... but then again' date=' I recall sometimes have to use headphones if want to listen to radio as that cable acts as antenna... RF from hell? Have you moved amp around to see if that might impact picking up the squeal... good luck and if find out what the heck it is, share with us for future reference...[/quote']

 

Thanks. I only own one set of phones at the moment, though now that I think about it I could try iPhone earbuds with a jack adapter (although I'd expect those to sound like crap under pretty much any circumstances). Good idea about contact cleaner. The room I'm playing in is not air conditioned & is swampy as hell (I don't keep any of my guitars in this room, for that reason). Thanks for the tip. If I can't solve the problem, my wife will just have to suffer through actually hearing me play... until she murders me.

 

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Inserting the jack connects the jack but also disconnects the signal to the amp stage. That system does not seem to be working properly leaving mains hum picked up by a floating input.

1. Try plugging the 1/4 adapter in on its own with no phones.

2. If it still happens then check the plug contacts, its wiring and any resistor that may be across it.

3. If the socket is mounted on the PCB as they often are these days resolder the mounting connectors as that is a very common weak point.

Edited by Chordite
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In addition to Chordite's and Emory's excellent recommendations, give the ear buds a try. Yeah, they'll probably sound bad, but the idea is to see if the hum disappears with them or not. If not, then the problem isn't the other headphones, but lies elsewhere. Trying the other "headphones" (ear buds) lets you eliminate (or confirm) one possible cause of the problem...

 

But I suspect it's not the headphones themselves, but the output jack or associated circuit. If cleaning the jack (contact cleaner) doesn't work, then move on to Chordite's suggestions.

 

 

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Headphones can't cause buzz. They are output devices. Depending on their sensitivity they may make whatever hum exists more easily heard but they aren't the source of hum.

 

If you unplug your cord from the amp. If the hum goes away then either the guitar or the cord are poorly shielded and you need to improve the shielding.

 

If the hum remains then the amp might be at fault. If the hum didn't change when turning that tone knob I'd suspect the power supply caps weren't smoothing. Some amps have thin or open chassis designs which lack the shielding and allow noise to contaminate the preamp. It would need to be early on before the first gain stage however. Again, the tone pot on the guitar isn't going to change the level of hum after the first gain stage.

 

Dollars for donuts the hum comes from a poorly shielded guitar or cord. Fender type single coil guitars are notorious for producing hum. You may hear a reduction when two pickups are selected and the pickups humbuck, but most use unshielded wire. Leo Fender wasn't an electronic tech, he was more like a Henry Ford who designed a Model T and never modernized his designs. Leo kept the same flawed wiring even after musicians started gaining the guitars up and hum levels because a huge problem. All he had to do was use shielded wiring and much of the issues would disappear.

 

CBS Fender decided to cash in on their own problem by making noiseless pickup designs like the lace sensors. Again, all they needed to do was use shielding paint and ground the control cavities and it would kill most of the hum and have no impact on pickup tone.

 

If you use some other guitar, with humbuckers, there could still be an issue with the string ground as onelife mentioned, or it could be excess exposed wiring inside. It could also be the cord. Budget cords may only have 70% shielding. You always want to use cords with 95% shielding or better. Thick shielding is something you can typically see when you unscrew the plug covers and look to see how thick that shielding is.

 

The cord shielding and the guitars shielding all connect to the amp shielding which is grounded. all the circuitry in the amp is shielded by the chassis and the cord and guitar shielding are an extension of the amp chassis which prevent hum from getting to the core signal wires.

 

They call this shielding a Faraday Cage as it was invented by a man called Michael Faraday back in 1836 and has been the basis of all audio designs since the first amplifiers and radio's needed shielding. https://en.wikipedia.org/wiki/Faraday_cage

 

when you hear hum its because there is a hole in that cage big enough to allow radiation in and contaminate the signal that then gets amplified.

Your hum is influences by the guitar pot so the problem comes before the preamp section of the amp - its pickups, wiring, string ground or cord. It can be any one or a combination of any or all. You'll need to isolate it down by trying a different cord or guitar. If its the guitar then you'll need to shield it to minimize the problem. Get some copper foil and shield the cavity and pick guard.

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