From: META000 <META@UNB.CA>
Subject: humbucker theory (was Ibanez hum)
Organization: The University of New Brunswick
Date: Sun, 4 Oct 1992 22:42:56 GMT

As usual, Don and R.G. set me straight.  (Maybe it's true. Maybe you
DO need an engineering degree to be a musician these days!)

I might point out that my windings are VERY sloppy. When I say
handwound I mean HAND wound. I hold the coil in one hand and the
wire in the other.  I suspect that, taking R.G.'s calculations about
length of turn into account, we really ARE looking at a 10%
difference in turn length between inside and outside turns.

Don mentions the phenomenon whereby pickups attain their
characteristic sound by virtue of variations in the magnetic
relationship between string and polepiece, and how the amount of
string length within the "eye" of the pickup determines timbre.  I
assume that when the wave length of a note is such that "upsy" and
"downsy" parts of that wave are each within the "eye" of the pickup
(or both "eyes" in the case of humbuckers), then the two components
cancel each other, leaving only those string vibrations that are
uniquely represented at the pickup.  Peaks and troughs of high
frequencies are so close together that they are usually somewhere
within 180 degrees out of phase over each polepiece, giving the
meaty, but lustreless, sound of a humbucker.

 I understand why the dimensions of the humbucker have become a standard
of sorts these days, given how desirable it is to be able to buy a
pickup and just pop it in.  Standards for cavities need not imply
standards for coil-spacing and voicing, though.  It seems to me
        that given how capable we've become at making eensy weensy
coils that can fit two to a single-coil-case, its surprising that
someone hasn't tinkered with an adjustable voicing pickup to fit in
a standard size humbucker chassis.  Technically, itought to be
possible to make two small coils,one of which could slide backwards
and forwards inside the chassis, resulting in the cancellation of
different frequency components.  The Fender humbucker (that showed
up on Starcasters and Tele's), has two sets of adjustable polepieces
so that one can create "angular" polepiece alignments (like a
Tele-bridge pickup in a humbucker case).  With one moveable coil
within a humbucker chassis, it ought to be possible to do the same
thing with one of the coils; i.e., one perpendicular to the strings
and one slightly offset at an angle.  The old Dan Armstrong guitars
(the see-through plexiglass ones) had a track along which a pickup
could be slid forward or backward to a different position to get
different "personalities".  The Turner guitar that Lindsay
Buckingham plays has a pickup that can be rotated to different
angles within its' housing.  So, the idea of "redefinable" pickups
is not new.  I guess people are just to used to looking at double
coil pickups in a certain way.

Another idea I had for a pickup, and just never got around to
making, was a "coil-swapping" pickup that utilizes 3-coils, two of
which may be swapped to produce either a side-by-side humbucker or a
stacked humbucker.  I discussed the idea with the guys atEvans
pickups, when I used to live near them a few years ago.  Evans said
that, in theory, it ought to work, but that he and many others, found
the sound of stacked humbuckers less than desirable.  Still, it
strikes me as an idea that might prove ideal for somebody,
somewhere.  The basic rationale is this.  Many guitarists try to get
a "single-coil sound" by cancelling one of the coils on a humbucker.
Although this does eliminate the within-pickup cancellation of high
end that usually occurs, it also results in a noticeable drop in
output, and loss of hum-rejection.  I thought that if the (please
don't hurt me, Don) IMPEDANCE of the pickup could be kept constant
when switching to single coil mode, then the drop in output would be
reduced (although still there to some extent).  If that extra
impedance could be provided by an additional coil in hum-bucking
mode, so much thebetter.  Admittedly, I haven't tried anyone else's
stacked humbucker, and it's been so long since I've played with other
musicians, that I don't know if the stacked humbucker I made is some
kind of freak of nature, or whether my standards have drifted so far
that I actually like what others dislike immensely.  In any event,
it functions just fine as a pickup, disregarding aesthetic
prferences.  If one stuck it in a chassis alongside another coil, so
that, from the side, it looked like two humbuckers, piled on each
other, with an empty bobbin on the bottom of one side of the pickup,
you'd have my coil-swapping pickup.  Let's say that the rear pair of
coils form a stacked humbucker.  If the bottom coil of that pair is
replaced by the coil at the other side of the pickup, we now have
(assuming they are wired the right way), a traditional side-by-side
humbucker.  Alternatively, if it's true what they say, that stacked
humbuckers really suck, then one could always try the following.
Wind a standard single coil Fender-style pickup, but tap it after
half the turns.  Since many of the turns would be at both magnetic
poles (i.e., the north and south ends of the polepieces), this
tapped coil, in tandemwith the extra coil on the front of the pickup
(where all the turns would be primarily at one magnetic end) should
constitute a reasonably, but not perfectly hum-rejecting pickup.
When the extra coil is deleted and replaced with the remainder of the
windings on the main coil, we should get a standard single coil
sound, hum and all.

There you go, some ideas for novel pickups.

Now, if someone could only explain to me how Lace pickups reject
hum.

Mark Hammer