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Cronic buzz on Guitar pickup


MarkBarl

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Had a strange one at the weekend. We were playing a wedding and once set up all was fine and quiet until the guitars (Bass and electric) were turned up and there was a chronic buzz being picked up. If we turned the guitars down via their volume knobs the buzz disappeared, so it was definitely being picked up by them. If you moved about, the buzz might fade a bit but was still there. No fault on the guitars, used at a different venue since and all Ok, lights switched off and no difference made. There must have been some serious EM in the room perhaps from the AC inverters. The PA is all balanced inputs and outputs and suffered no buzz at all. Any speculation on what it could be and how to mitigate it if we encounter it again?
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a band I knew ( fenders if it makes a difference) had terrible issues in a club and had to stand at 90 degrees to the stage to reduce hum.

 

after the gig, on loading the van, somebody realised that there was a huge pylon and cable swooping over the building, roughly parallel to the stage

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Humbucker guitar pickups have two coils. One which picks up the magnetic field changes from the strings and a second which does not. Both coils pick up all the external magnetic field changes but they are connected out of phase with each other so it cancels out. So fitting humbuckers would be one, rather expensive solution!

 

Dave

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As a guitar player I've found that the worst culprit is lighting dimmers although this is more of a buzz than a 50Hz hum.

 

The BIG dimmers that older theatres have play havoc with my guitar's single coil pickups.

 

Our bass player suffered a lot with this and improved things massively by fully screening the wiring compartments in his bass with sticky backed copper foil etc.

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It might have been an induction loop, the room was one of those corporate types with a partition to divide it into 2 rooms and had some install ceiling mounted system, if it had a loop switched on with nothing connected, that might explain things.

Thanks for the replies.

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Humbucker guitar pickups have two coils. One which picks up the magnetic field changes from the strings and a second which does not. Both coils pick up all the external magnetic field changes but they are connected out of phase with each other so it cancels out. So fitting humbuckers would be one, rather expensive solution!

 

Dave

 

Stacked humbuckers work in different ways but the basic principle is as you suggest with the bottom coil picking up a lower signal (or no signal) from the strings than the top, a bit of clever (and often secret) jiggery-pokery results in a reasonable amount of hum cancellation but at the cost of a change of tone from true single coils.

 

Conventional humbuckers (with side by side coils) provide nearly prefect hum cancelling properties. Both coils pick up the magnetic field changes from the strings more or less equally, they are wired in series but out of phase and have the magnets reversed in one coil relative to the other. The result is that the wanted signal from the two coils is in phase and adds to give, usually, a higher output than a single coil but any EMI is also induced equally but out of phase in the two coils and thus cancels.

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Makes you wonder why they are called humbuckers, innit?

:guitar: :wall:

 

http://www.blue-room.org.uk/public/style_emoticons/default/biggrin.gif Aside from the possibility he named them after some very peculiar horses I guess Seth Lover came up with a catchy name (and a pickup which actually did what it said on the tin) and everybody else has jumped on the bandwagon. Anything with stacked/silent coils or other clever stuff must be a compromise (though Wikipedia says the original 'hum-bucking' coil was an EV invention in 1930 and a 'stacked humbucker' was 'invented' by an employee of Baldwin Piano Company for use in pianos in 1938), SL's original 'hum-bucking' guitar pickup worked just like balanced mic/line connections by utilising common mode rejection (ok, it doesn't deal with EMI getting into the lead between the guitar and the amp but that's usually much less troublesome). In doing so it changed the tone of the pickup and achieving the same effect without changing the tone of a single coil pickup is another basket of fish.....

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