To solve a problem requires to analyze the cause.
We are dealing with four different kinds of external interferences --
#1. The basic sixty cycle hum
caused by single coil pickups.
How can we solve these problems?
#1. Use a dual coil system
to neutralize external magnetic fields. Shielding does not reduce the
Now let me address some
possible side effects of shielding. Here again we have to ask the question--
Changes in tone quality are
caused by eddy current
interferences while loss of highs are caused by capacitance. Losses of
highs due to capacitance are virtually impossible. Only if you use extremely
long shielded, high capacitance leads from the pickups to the controls,
there may be some loss of treble. On the other hand, eddy current interference
can change the tone dramatically. Shielding the cavities with copper or
aluminum tape does not cause any eddy currents.
So, what causes eddy current
#A. The Tele bridge mount.
The magnitude of eddy currents
depends on the thickness of the material, the proximity to the coil and
the kind of metal. Copper or aluminum under the pick guard or shielding
the cavities will not cause eddy currents, but wrapping any conductive
tape around the coil will. Aluminum will cause higher eddies than copper,
steel or brass, but alloys like nickel-silver or 300 stainless steels
cause virtually no eddies.
Are eddies good or bad?
I compare eddies with salt
in a soup. One of the sweetest sounding Strats I ever played was a ‘65
Strat which had a .025” stamped sheet aluminum plate as shielding under
the pickquard. No loss of highs at all, but the higher midrange was slightly
reduced. I use eddy current interferences to fine-tune pickups, but interpreting
the specs of a pickup is as complicated than reading an EKG!
Copyright © 1996-2010 Bill Lawrence