ampage Tube Amps / Music Electronics	For current discussions, please visit Music Electronics Forum.

ampage archive

Vintage threads from the first ten years

Dummy Coil!

:

9/11/2002 5:02 PM
Frank DeSalvo	Dummy Coil! Can I wire a single coil in parallel to the one on my G&L and place it under the pickgaurd and achieve a hum-free single coil tone? ~F

9/11/2002 6:14 PM
Mark Hammer	Yes. (terse enough for ya?)

9/11/2002 6:58 PM
Frank DeSalvo	I'll take "turse" anyday! Thanks! ~F

9/11/2002 7:01 PM
Frank DeSalvo	Waiter, hold the "U" and I'll have a slice of "E"... Damn these keyboards! I hate typing! ~F

9/24/2002 6:27 AM
Steve A.	Re: Waiter, hold the "U" and I'll have a slice of "E"... Frank: We are fresh out of "E's" but will swap a "D" for the "S"... [grin] Steve Ahola

9/11/2002 7:02 PM
SK	Re: Dummy Coil! sorta, it will affect the tone. I would consider finding a cheap plastic bobbined singlecoil and removing the polepieces/magnet...

9/11/2002 7:47 PM

I've been interested in how this all works. It seems there has to be somewhat matched coils in order to have the maximum amount of hum cancellation. So for example, using a strat pickup to cancel hum for a P-90 may not be as optimal as using another P-90.

More interesting, it seems that the coils not only need to be matched for resistance, but also for impedance and/or inductance. I found this may be the case by removing, one by one, the six polepieces from one coil of a humbucker. As each polepiece, a steel slug, was removed, I found that hum became louder and louder until, with only one magnetically active coil (and essentially one magnetically inactive dummy coil), the humbucker was no longer bucking hum, but just as noisy as a single coil. Replacing each polepiece, one by one, incrementally lowered the hum level until, with all the polepieces back in place, hum levels were back to the typical humbucker level.

I surmised that removing the steel polepieces changes the inductance and thus impedance of the coil, making it imbalanced with the other coil, even though both coils were still matched, at least for DC resistance. Will the gurus explain what's happening here?

BTW, what I did to the humbucker I experimented with, was remove three polepieces from one coil and three from the other coil, keeping the coils balanced (at least as far as hum is concerned) and thus hum cancelling.

In an active system, perhaps what is necessary is the correct *mix* of dummy/active coils in order to achieve maximum hum cancellation. Perhaps coils matching in this case would be less critical in this instance. Anyone have any thoughts on this?

Page 1 of 4