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Hum from humbucker?

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10/6/1999 11:33 PM

Hum from humbucker?

I am using a SD Custom custom humbucer in my ESP, and it hums like a single-coil, especially at high gain. The hum is sensitive to orientation wrt the amp, like a single coil. I have inspected the wiring and both coils are connected in series and are functional. Anyone out there have any insight into what might be causing this? The other two pickups are SD cool rails, and don't hum in the least. I thought humbuckers were supposed to buck hum! Thanks in advance for any help!

10/7/1999 6:08 PM

My guess is that either the pickup is defective, or somehow you've made a mistake in the hookup wiring. You sain you verified the wiring and both coils operate. Maybe one has a partial winding short, so that when connected to a full length winding there is a net imbalance responsible for hum pickup. You may have connected the wire colors correctly, but accidentally have one coil shorted out (coil tapped).

10/8/1999 8:59 AM

I had a quick look at the SD Tone chart pages.
The Custom-Custom has an AlNiCo2 bar magnet
underneath the coils. This is the cause for the hum
since AlNiCo has a high permeability and works - so to
say as - a bridge for external magnetic field lines. They flow through the core of the first coil, then through the
magnet and finally in opposite direction through the
second coil. In this case hum adds due to the bar magnet
and the humbucking effect is reduced.

The Cool Rails have ceramic magnets under the coils.
The permeability of ceramic is near that of vacuum and
thus the external field lines flow through both coils
in the same direction and hum cancels most effectively.

I was really disappointed when I realised it, that nobody
of the pickup gurus (SD, DiMarzio, etc.) spends a word on the noise level of their pickups. It's impossible to
find a brighter (PAF style) humbucker with a ceramic magnet.

Somebody who exchanged the AlNiCo bar magnets of an SD Jeff
Beck and a Trembucker '59 against ceramic......

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