A Study On Extended Pickup Configurations And Voicing last
update: Mar 29, 2020
by H. Gragger. All Rights Reserved. All
information provided herein is destined for
educational and D.I.Y. purposes only. Commercial
re-sale, distribution or usage of artwork without
explicit written permission of the author is
strictly prohibited. The original units with
their associated trade-names are subject to
the copyright of the individual copyright or
trademark owner. The Author is by no means
affiliated with any of those companies. References
to trade names are made for educational purposes
only. By reading the information provided here you
agree to the Terms
Bass. A bass
launched by Leo Fender† 1980 after his
departure from Music Man. As salesman rap
has it, it is the best, most versatile bass
Leo ever made.
The foundation of the L-2100 is a pair of
Magnetic Field Design™ (MFD)
humbuckers and what they call the Tri-Tone
system: a trio of mini toggles for
pickup selection, series/parallel signal
routing and active/passive operation. (It
defies logic what is tri-tone about it).
The output of those pickups is massive due
to the MFD design, but very bass heavy. Some
folks from the D.I.Y. community have
invented schemes to exploit the idling
potential of creative coil interconnection
beyond plain parallel native mode and all
fancy tones that are possible by that, all
with some shortcomings and trade-offs.
In the following I will show options
previously not found or at least not
published. In the process, many traditional
concepts were put to the touchstone, new
subjects arose and were evaluated on behalf
of decision making. They will appear in a
loose, not necessarily consecutive order.
Sometimes they created more questions than
giving definite answers. A
work in progress
- hence the title
Although this may serve as a cook-book
recipe for modding, I hope that, since an
increase of options is likely connected to
an increase of confusion, the kind
reader chooses wisely what promises to serve
her/him best, before firing the soldering
(Rohde&Schwarz) HM8118 Programmable
LCR-Bridge (L and C)
PM2519 Precision Multimeter (R)
A note on the measurements.
This RLC device is, despite its name, not a
classical bridge instrument. It measures impedance
and phase angle of the device under test and
identifies the component according to a phase
diagram (positive phase values: inductance, zero:
resistance, negative: capacitance).
Since a guitar
pickup comprises a parallel resonance circuit
(inductive on lower frequencies, capacitive on
higher frequencies with zero at the resonance),
the device operates in parallel mode. Impedance
changes wildly over the frequency range, and so
do readings for L and C. With a conventional 100
Hz reading for L you may get a reading of 22H at
a meager phase angle of +22deg. Readings become
fairly consistent around some low kHz value for
L, while the one chosen was the one that yielded
the best phase readings. C measurements yielded
the best phase values at the top selectable
frequency. Resistance is measured in DC with a
respectable instrument. All values are
rounded to the nearest comma. Precision beyond
that was considered ridiculous.
Also, I just measured one of the pickups (neck). Virtually all
low-budget commercial L-C Bridges use a
different measurement principle and a limited
set of frequencies, and since nobody documents
those things, it is to be questioned how
reliable those measurements are. Indeed, I do
not claim perfection too, since there is always
leeway. However, those values may serve as a
In Harmony with
the information on Guitar
Lettersthe north coil is the one
that attracts the south pointing compass
needle approached from the
string´s side. According to this
specification the coil closer to the neck
(Yel-Grn) is a north coil (The side of the
pickup that has two mounting screwspoints towards the lowest string).
misst, misst viel Mist!"
saying (a word game meaning:)
"Who measures a
lot, measures a load of horse-dung!"
Back To Index Nomenclature: New
Switching Functions Demand A New Name For The
With the advent of
complex coil interconnection circuitry, some
nomenclature commonly used within this context has
to be revised to describe phenomena previously non
If those terms are not
made clear, it is impossible to understand the
For example, in a basic
two pickup system consisting oft two single coils,
one at the neck and one at the bridge, one may find
a 3-position selector switch, one for neck, one for
both and one for bridge position.
Now this may be
classically called pickup selector switch,
which, since it has no secondary function, also
serves as source selector switch.
instance, a Les Paul type guitar traditionally
has a pickup selector toggle switch, maybe
adorned with some coil splitting functionality
restricted to one physical coil cluster. Coil
selection (and thus interconnection) is
equivalent to the source selection.
A classical Strat has
three single coil pickups and is equipped with a
three-position switch. Each position selects one
coil. Later models have a 5 position switch that
also allows for intermediate settings and
combinations of adjacent coils. Still the coil
selection (and thus interconnection) is equivalent
to the source selection.
Even later connection
schemata arose that made complex interconnections
possible like series and non-adjacent coils. Those
clearly exhibit a distinction between coil (=
pickup) selection and switch position. A switch
position begins to select a fixed sound-scape.
This is a performance selected feature rather than
a recording session feature, which is the approach
Dan Armstrong has taken with his Superstrat
switching scheme. Lester Polfus (see later under
“voicing”) has explored a similar path with his Les
Paul Recording guitar. Similarly, one
tinkerer modified his L-2100 with three
three-position switches that allows for all
imaginable interconnections – not necessarily a
people have gone the way to the end by also
incorporating individual “voicing” caps into those
positions or dummy coils where needed.
In the case of the
modded L-2100, the previous pickup selector
switch (the one closest to the neck) loses its
direct coil cluster
fixation and becomes a source selector
switch. The center switch (series/parallel)
maintains its original functionality, but complex
coil interconnection, beyond fixation to a cluster
of adjacent coils, is transferred to a newly
introduced three-way switch, best called parallel
In this case, any pair
of coils, possibly spreading over non adjacent coil
clusters, may be selected (such as inner pair
or outer pair), which if source selector is
in both mode will be a humbucking (parallel)
pair, but in solo (neck or bridge mode) a single
coil. See the
reference chart later on.
For clarity, a
distinction has been made between coils belonging to
one physical cluster of adjacent coils (hereafter native
mode) and two physical units (hereafter cross
According to the
previous differentiation between performance
and recording switching schemes the scheme
presented in the following is positioned in-between.
It is experimental and work in progress. Ideally,
there should be a “P”, a “J” and a “S” position and
The widely used
nomenclature „single inner“ resp. „single outer“ is
a misnomer, since it indicates single coils, but it
is actually a hum canceling pair (for both
mode at least).
nomenclature stems from the fact that one coil
out of physically stacked up pair is used
together with one single coil borrowed from the
pair across, hence the name cross-mode.
It is replaced by the
terms inner pair and outer pair, referring
to the physical arrangement of 2+2 coils at the neck
resp. bridge side. "Inner" and "outer" makes only
sense in reference to this arrangement.
Nevertheless, true single coil
operation for all four coils is possible, it
comes into the bargain. Refer to the pickup selection
chart for more information.
Back To IndexEvaluation:
Why Do Players Consistently Revert To
Some users of the
L-2100 insist on using it passive, with volume
and tone pots dimmed. Why? We want to understand
this, because there may be things we can
optimise into the bargain. This also builds some
foundation for any alleged voicing later on.
to technical explanation is inevitable.
Every pickup basically is
a resonant R-L-C circuit (winding resistance,
inductance and winding capacity), which forms a
higher order resonant low pass. Guitar
Letters explains this well.
Such a circuit on its
own will exhibit some ringing at the cutoff
frequency, sometimes substantially dependent on
Although this may be
perceived as extended treble range, the ringing is
usually not appreciated. Think of a wah pedal
halfway back at a fixed position – good for an
effect, but not for always.
Technically this peak
can be modified by two factors: a parallel
cap and/or a parallel resistance.
An additional cap will
add to the winding capacity and shift the peak
towards lower frequencies. An additional load
resistor will bring the Q down and with it the
Our pickup always
exists within a practical electrical
environment, in the vicinity of a volume pot and a
tone pot at least, so a certain load resistance is
always there. Humbuckers are more sensitive to
load than singles, that´s why you always see recurring
pot values of 500k versus 250k in single coil
A passive treble cut
pot, when at 100%, presents some more load, say
250k, which totals in 120k together with the
volume pot for a single coil. Turning tone down
just a little may be enough to remove the hump and
thus the ringing. (Remember: that´s what many
players say they like...).
Turning it down
completely will bring the tone cap in parallel to
the winding capacity and create an artificial
resonance at a ridiculously low value, which is
unfortunately beyond good or bad to be useful for
stock cap values. All passive guitars work like
Now we have not yet
plugged the guitar into an amplifier in our mind
Adding a cable adds
more capacity and more load resistance dependent
on the pot´s settings, so that there may be a
sweet spot of all settings that sounds good. Of
course passive circuits also introduce other
imponderabilia that can wreck the signal.
That´s where the
active mode enters. However, this way has not been
gone to an end with the L-2100´s stock circuit.
Dropping all load factors – too much brightness,
too much ringing and that consistently. Since the
built in amplifier is configured for some treble
boost even in the normal mode, letting alone the
treble boost option, this can only worsen things
some small capacitors and resistors before the
buffer can tame any of those things and thus
introduce all of the merits of passive mode
without its drawbacks. It so happens the L-2100
already has a 1nF cap in parallel by definition
(this is the one soldered onto the bass pot).
This, to my taste, is too
hefty. See later in the section on voicing.
extended switching circuitry offers some
unassigned positions for that into the bargain.
procedure is really that easy and cheap, it
wonder if the ones who devised the circuitry did
only have their sales numbers in mind, saving caps
worth cents... It brings more
money to sell another instrument rather than
have just one that does all you want...
Back To IndexEvaluation:
OMG Mode, More Boosts That Are
None And Boosts That Chase Their Own
In 1982 Leo Fender filed a patent (US.-Pat.
4,319,510) for splitting humbuckers that do not have
all leads accessible, also known as three wire
This is in
fact astonishingly simple. As different to
shorting out a coil entirely, a capacitor shunts
frequencies out. Choosing the capacitor´s size
wisely, 50 Hertz hum cancellation remains
intact. However, higher frequency hum (such as
from switching electronic appliances) will not
cancel. Making the capacity smaller will work
better, but let increasing amounts of low
frequency content through.
On the L-2100 basses, Leo
was probably trying to achieve a pseudo
single coil sound, which is less boomy, and in
the verge of trying different caps found the bass
boost attractive. How the term OMG came about
is unknown, since this is recent social platform
By shorting some of the
treble content out, bass content appears louder.
Although just cutting and not boosting, this mode was
called „bass boost“. All is relative. Unfortunately,
together with the fixed 1nF voicing cap, this mode
sounds pretty dark. Maybe interesting for some retro
sounds, but not for contemporary sounds.
Again this is no real coil
splitting, it is a humbucker wired pseudo
single coil. There is no coil shorted out with a
hard wire bridge.
OMG mode lead to many complaints by musicians, because
hum suppression is, like in all single coil circuits,
inferior. Moreover, Leo could have at least the center
position (both) humbucking, which was recognized by the DIY community,
but never cured by the company. Conversely, they
decided to drop OMG entirely on later modes, such as
specimen of the bass.
My personal opinion is that
the series wired pickups are powerful enough the way
they are - without "boost", and that it is somewhat
awkward to generate a bass overload first and then use
treble boost to remedy that. The cat bites its own
When working with new modes
it became obvious that the volume drop between serial
and all other modes was a nuisance, requiring a
permanent re-adjustment of the volume pot.
previous owner had made a feature out of this flaw
by calling it the „rock switch“ - volume boost.
Hmm. Rather make a small, adjustment on the volume
pot if needed.
Of course, OMG does not
harmonize with that, but this was deemed questionable
anyway as elaborated above. There is no need for
pseudo humbucking if real coilsplitting is at hand.
However, by bypassing the
dropping resistors with a cap, some partial "boost" of
high frequencies can be achieved. Again, this is no
boost, but treble content gets less suppressed. Why
making half hearted attempts towards single coil sound
when a brighter sound can be achieved another way
while maintaining full hum canceling functionality?
Back To Index Exploring
Existing Groundwork And Setting New
By far the most of the
mod tips I
could find are limited to the installation of a
three-position (on-on-on) switch, selecting between
serial, parallel, and one single coil combination,
and possibly a push-pull pot for extra switching,
which basically replaces the existing two-position
All the those attempts
to maintain the original possibilities (serial,
parallel) plus at least two cross-connections
(inner/outer pair) without inviting other penalties,
There is a limited amount
of switching possibilities that manipulate the „hot“
side of the pickups, and even more limited for the
„ground“ side, since G&L have decided early to
connect a screening ground plate to one of the coils
(green wire). Drilling some holes for extra switches
or the like was not an option, being commonly
associated with a loss in resale value.
A guy named Femto
has devised a switching method using the stock
serial/parallel switch plus an extra on-on-on switch,
which would have to take the active/passive switch
location (this one moving to the switch of a push-pull
pot), yet functionally being very similar to the
method devised by me.
manipulated the ground sides of the coils, which,
although this appeared to work for him noise-wise,
might invite trouble due to the ground plane floating,
that is mounted to the bottom side of each physical
unit. It is likely that people were reluctant to adopt
his method because of this fact.
However, combining both
high side and low side switching turned out to work
flawless with a compatible switch layout.
The goals for modification
thus were set to be:
exploiting all coil
maintaining the existing switch layout to avoid
degrading resale value
a nutshell: the newly devised switching
scheme keeps the original serial/parallel
switch, except that the range of available
parallel modes has been expanded, determined
by the setting of the parallel pair
selector configuration switch. Dependent
on the setting of the source selector
switch, all four individual coils can be
addressed in true single coil mode too.
The parallel pair
selector switch physically resides in the
space, that was previously occupied by the active/passive
switch, whose functionality moved onto a push-pull
switch linked to the volume pot knob.
boost mode has been dropped as mentioned
(click on the picture to load
The parallel pair selector
switch allows for three positions:
pair (lever towards the neck,
pairs one of the neck with one of the
here referred to as cross mode)
(lever centered, pairs physically
adjacent coils, here referred to as native
pair (lever towards the bridge,
pairs one of the neck with one of the
bridge coils, here
referred to as cross mode)
When both is selected on
the source selection switch, those
positions are hum canceling. Since the
coils are arranged N/S - N/S starting from
the neck, the cross-mode arrangements xS
- Nx (inner pair) and Nx-xS
(outer pair) are hum canceling as well as
the native N/S arrangements.
Note: In solo
mode (e.g. neck only), out of the selected pair,
although both coils are active, only one will
contribute to the output signal - the one
residing in the source selected (neck in the
example), hence a true single coil. This
one is subject to hum as all single coils are.
Determining which one out of the two adjacent
coils is currently active is slightly awkward
and is not always in direct relation to the
switches´ lever position due to the fact that
one has been eliminated out of a cross-pair.
Logic has been optimized in so far that the
lever points towards the inside of the guitar
body in inside pair mode and
towards the outside in outside pair
mode. Thus, only if bridge solo is
selected, the parallel pair switches´
lever points to the correct single coil, but
this is reversed for neck. This is
inevitable and a small problem.
Humbucker pairs in cross mode may have an
slightly inferior hum suppression capability due
to a greater “magnetic aperture”
serial mode chart (click on the
icon to download)
The threading of the
4pole on-on-on switch I used (Knitter Switch
MTA 406 PA) appears slightly shorter than the
C&K variety, so it needed to go slightly
deeper into the wood. The usage of any machine
operated drill was avoided at all cost, since this
eats itself into the wood way to fast. A few turns
by hand were enough.
Note:knitter switch MTA
406 PA datasheet
information is erroneous on the pin layout.
The layout is equivalent to the ubiquitous C&K
7411 and Multicomp 1M46
switches. WARNING: I just received two switches
from them that DO adhere to the Datasheet.
Measure before you solder!
Update: refer to a special
document on those switches for more
I looked for a
good quality push-pull volume pot with a solid
6mm shaft like the other pots on the L-2100.
There exists one from Alpha, but this seemed
unavailable. The one chosen is a CTS 250k
PUSH/PULL 3/8", which fits just perfectly
inside the cavity. It has a very smooth volume
reduction over its travel and also exhibits the
same friction to motion as the others do. Its
thread too, is a bit short, but using a bigger
diameter lock washer that sits on the pot body
rather than the small mounting rim works well.
It also comes with a
1/4” knurled shaft. Unfortunately, dome knobs for
knurled shaft pots are not available hereabouts.
Fortunately, you can buy small brass sleeves
that slide over knurled shafts and make 1/4”
solid shafts out of it. The dome speed knob´s bore
was increased to 6.5 mm with a stock steel drill
and this works great.
The ceramic treble
bleed cap was replaced by a good quality cap
on the go.
The push-pull switch
activates passive mode when pulled, but this is a
matter of taste.
The barrel output
jack was replaced by a new one since it
permanently interrupted the signal when the
slightest sideways pressure was applied onto the
Removal was easy with a screw extractor (the type
that has reverse „threads“ on it). The jack does
not even get destroyed by this. It just screws
out. Unfortunately that the new jack appeared to
be no cure. Signal went intermittent when you use
a long flange plug and apply sideways pressure. So
using angled plugs and folding the cable back
under the strap is paramount if the kind reader
insists on keeping the barrel jack.
The barrel plug is just inferior. A disgrace
for such an expensive instrument. It is
beyond comprehension why they used it, probably to
distinguish themselves more from other
manufacturer´s products visually. Internet
forae are full of complaints about this nuisance,
and many owners have decided to replace it by a
on the picture to
Soon before long,
the barrel jack was replaced by a standard
jack together mounted onto a metal football
shape mounting plate. The procedure is
An oval (a.k.a. football) jack plate together
with a standard Switchcraft short ¼“ jack was
mounted (a Gibson style square jack plate
appeared almost too big, extending into the
beveling) – end of discussion and end of
Folks doing the same before worried that it
may be a problem to drill a large enough hole
without slipping and damaging the guitar
finish. Not at the least. I used a stock metal
step drill in a slow running
cordless electric drill to enlarge the hole to
20mm just at the rim, yielding a somewhat
A 20mm Forstner bit now fitted
perfectly into this bore, so no danger of
slipping. The wood is soft enough that a very
slow drilling speed can be used. Some more
gentle drilling and the hole was through. No
chipping, nothing, a razor sharp cutout. A
five minutes procedure and painless.
omission was the unscreened electronics
compartment cover plate. This is ridiculous,
since the compartment itself is paint screened.
A piece of self adhesive metal foil was applied to
the plastic plate. A small strip of copper
foil was folded and glued over the cavity´s edge
and soldered onto a ground point so that it makes
contact to the cover´s foil, at a location near
the output jack where the back plate is screwed
onto the body for good contact.
The wire to the preamp
that does the treble boost was be removed.
The preamp itself got
wrapped inside a piece of self adhesive tape to
prevent contacting anything.
The cavity is now quite
crammed, but serviceable since I left enough slack on
While not being a new feature, this subject
belongs to the changes made to the instrument:
during slap playing, the E string easily thunders
into the pole pieces, with an according sharp snap
from the amp. With the pickups fully down and the
spiral spring underneath fully compressed, they
still protrude about 10mm from the body. The
remedy was to shim the neck slightly so that all
strings are elevated somewhat. This of course
requires raising the bridge again to restore the
Now the switching stuff has all been sussed, a
whole new can of worms is torn open – voicing.
Browsing through the settings invariably involves
a change in perception of treble, mid and bass
content, some subtle, some heavy. A minimalistic
guitar setup will be equipped with a treble
control, which, as we saw earlier, can tame the
resonance peak and cut some high. The second
resonance that occurs when the pot is at zero
(caused by the treble cap), is usually too extreme
to be useful. So those positions remain
essentially raw and untreated sonically.
Lester Polfus, better known as Les Paul,
was confronted with exactly the same problem back
in the seventies with his Les Paul Recording
Guitar, and he solved it by providing a
rotary switch with an array of caps, not different
to the C-switch devices available today.
He aptly called his guitar recording,
since, in a performance situation, few would have
been able to cope with all those knobs and
These days, things head towards performance
selector switches (such as in those fancy
aftermarket 5-way Strat switches), which select
between “sounds” consisting of useful coil presets
and potentially voicings.
This means a deliberate step backwards from Les
Paul´s idea for the sake of simplicity and
performance, but he wanted it all.
Despite thousands of schemes available on the
internet, rarely anybody exploits the whole
potential of tone shaping those positions.
A 1nF cap (stock) is already active for all
positions, which to my personal taste was too
much. It was replaced by a 680 pF Styroflex cap.
This made the series signal even more pristine,
alleviating the need for an active treble boost
First listening tests on the untreated parallel
modes and particularly the single coil modes
revealed a pretty trebly, sterile tone, reminding
of early Stanley Clarke recordings. A test
jig was put together quickly, nothing different
than what is known as the commercial C-switch
or tonestyler (a rotary switch with a
rake of small caps) and small caps in the nF range
(around 2.2nF) were found for each position
that brought the resonant frequency down to an
pleasing value before tone was becoming honky.
Naturally, single can take more capacity than
parallel, but due to the lack of unoccupied
switching positions a compromise value of 2.2 nF
was chosen for all non-series positions. Tone gets
much more mellow by this, without sounding honky
The acute reader will have noticed, that this
demands another switching element in the series/parallel
switch, which is non existent unfortunately, but
some crafty solution has been found, remaining my
ace card for the moment.
Any excessive resonance peak (“Q”), perceived as
stinging quality, can further be tamed by dialing
the treble pot down just a hair, long before the
treble cutting action itself comes into play, so
individual Q-shaping resistors were equally
abandoned due to the lack of switching positions.
"Passive tone" despite buffering was
re-contemplated. A typical guitar cord may exhibit
100pF/m capacity, a 6m cable will thus easily have
600 pF. Together with the built-in load 1 nF
capacity this is a fairly hefty load for a passive
system - too big for my taste as mentioned, but
some seem to like it.
With all this extra
switching, you can always leave the parallel
pairs selector in center position, in which case
the bass behaves exactly like stock, leaving
aside volume equalization and voicing. It
certainly looks stock. Flipping the parallel
pairs selector into another position,
you´ll have powerful presets ready at the flip
of a switch.
after equalization, seems subjectively
fairly constant across the different pickup
modes. It is still slightly bigger in serial
mode, but was left at that.
once loudness-equalized, a parallel mode
(provided using active mode) does sound very
similar to the corresponding serial mode.
This is probably where the axiom louder
sounds better is striking. In fact
they are so similar, that for a future build
series mode may be dropped entirely without
With the switching given,
all extended pair modes (inner and outer
pair) are parallel modes. Theoretically,
there is a possibility to connect those in
series too, but little promises to be gained as
and single modes do cope better with passive
mode if an additional load is present.
still the most bassy, but with an increased
clarity due to the bypass caps and the
reduced stock voicing cap. With some hundred
picofarad worth of cable capacity, tone
heads towards dark as expected - which
is why we go active for a start. Parallel
and single modes however do cope
better with passive mode if an additional
load is present.
modes sound very beefy and growly. Do
they remind of a Stingray? Maybe. People say
not even all Stingrays sound like a
modes have a different mid-range compared to
all other modes, even compared to each
other. There for sure is a certain mid-scoop
that the ´Ray´s have too.
(bridge) mode reminds of a J-Bass, but
is prone to noise as expected despite
shielding (this helping nothing against
magnetic interference...). Any individual
single out of the two adjacent pairs can be
activated, although it is a bit awkward to
select them (see the pickup
sound very raw and into-the-face. Very
attractive too. Again, P-bass is not P-bass,
J-Bass not J-Bass, a single pickup
sure gets into their ball park.
I decided that a general
load simulation was neither necessary nor
useful. Leaning more towards modern
sounds, passive mode was not considered
attractive, but if one wishes, one switch
position is free on the active-passive
switch (volume push/pull switch) which could
activate a dummy load. In this case, active and
passive tone would not differ much, but passive
tone (as mentioned above) could be reproduced
reliably and repeatably independent of
subsequent loading circuitry.
All of those features
accessible with the new circuit have their
merit, but time will tell if the increase of
switching options or -methods itself is
a blessing or a curse.
After some playing, the single coil modes do not sound
particularly attractive or reminiscent of other basses´
sounds*, but they are different and interesting
and may as well be used. Unfortunately they are prone to
hum. Maybe, due to the powerful nature of the pickups,
more than others. I tried to do something about this and
made up a large area aircoil (not unlike the Suhr silent
coil) to passively cancel out hum frequencies.
* Maybe I expected to have
a Precision sound or a J-Bass sound
at hand, and while it surely crosses into that
territory (like any similarly built pickup in that
position will...) I found there is no such a thing
like THE XY sound. There are several
web sites that try to carve this out and they had to
admit that they failed, because over the years so
many models with different body and neck woods resp.
shapes and surely differently wound pickups had been
made. This can´t be generalized.
back plate, an epoxy bobbin with an aircoil
on the picture to
This worked and continues to work flawless on my
Stratocaster. It makes it virtually hum free
without changing tone.
Unfortunately, due to the heavy signal coming
from the L2000´s pickups, the aircoil with a
typical rate of turns is too weak.
on the picture to
The inside is covered with foil for screening
purposes. Can be detached from the electronics
PCB. Weight is negligible.
on the picture to
devised a crafty active circuit with switch
position detection, dynamic phase
reversal and adjustable gain. To the left
you see some C-MOS IC´s that detect
switch positions. Hum cancellation is
only active during certain positions.
This part also dynamically
connects voicing caps dependent on the
switches´ positions, so the newly gained
modes may stay balanced sonically.
Hum cancellation worked in some environments,
but made things worse overall. The
idea was dropped and basic functionality
restored. The empty sockets you see stem from
the IC´s pulled for this purpose.
remaining circuitry is entirely optional.
No need to change what is there.
singles do still hum, but the rest is
Now that all
active methods to eliminate hum failed, I find myself
back at the roots. While it is true that screening
won´t help against magnetic interference, it will
certainly help against electrostatic
interference. And true, some of what I hear,
sounds like a harmonic of mains (transformer
originated) frequency, without the fundamental.
I opened the pickup
cavities - and they are bare wood. Agreed, the guitar
was never intended to be used with single coils, but
even in humbucking modes it appeared vulnerable to
higher frequent noises. To cancel those the "aperture"
of the two coils is too big. People report that with
screening they made even humbuckers quieter.
I have plenty of copper
foil at home, but there is no space in those cavities.
So I bought a small bottle of Humbrella screening
paint invented by a German guy and allegedly preferred
by luthiers. This does not consume any noteworthy
layers with drying time in between is recommended.
With a small brush I even poked a little into the
tunnels that go from the electronics compartment to
the pickup cavities. The wires should be screened too.
(See my hints
further down on working with the paint)
MFD pickups from
on the picture
to load larger
(picture taken after cavity painting)
Take a look
at the pickup´s underside. There is a
massive copper base plate with two
green wires attached. One comes from
the coil, one leads to the switching
assembly. As stated above, the method
has devised to switch the coils
from the ground side was ruled out
previously due to the base plate grounding
problem, but it looks this can
be remedied no problem by adding a
separate wire to the base plate.
Soldering is no witchcraft,
make sure the extra wire is secured
against pulling strain. So his method
may prove useful in
some respects after all.
Painted pickup cavities:(click
to load larger
A few hints
for using the paint:
away from contacts. While the paint is
not super conductive, it is low ohm
away from cables. They advise not to
rely on the paint´s adhesion to
plastics, but it adheres to cables
While this does not harm the cable
itself, it might make contact
paint adheres greatly to rough
untreated wood. From lacquered wood
you can scratch it away with the
fingernail after drying. Be aware that
it stains blank wood immediately.
Rough up lacquered surfaces as
recommended, but be aware that steel
wool debris will go flying to all
magnetic parts. Better use fine
sanding paper if you have the pickups
in the vicinity like I had.
Reassembling the pickup cavities: (click
on the picture
to load larger
pickup cavities have two holes drilled
to hold springs to push the pickup up
(left arrow). A piece of foam pushes
back (the foam was already a bit
deteriorated and was renewed).
had to widen those holes slightly,
because the springs are really tight in
there. After painting with conductive
paint and re-inserting the springs prior
to assembly, I inserted small strips of
copper foil between the spring´s
windings (bottom arrow).
Once the spring pushes down and gets
compressed, the copper foil makes
contact to the paint. Since the foam
pads are right beside, those push down
too. The springs themselves work against
the bare copper baseplate, which by
itself is grounded.
the piece of copper foil on the right. I
wrap this around the piece of wire that
grounds the bridge (and strings), which
was already a bit recessed in the wood.
After assembly, I inserted a small strip of copper
foil in a crevice right beside the pickups to
contact the paint and measured some 50 Ohms
against ground. This is absolutely perfect.
Repainted electronics compartment: (click
on the picture
to load larger
compartment is insufficiently screened. There
is conductive paint inside properly, but
incomprehensibly, they failed to screen the
back cover plate. This is simply a matter of
applying foil to the plate, which conveniently
contacts the rim of the compartment - but not
on this guitar (see the pictures above).
G&L did not paint the rim with
conductive paint. But this can easily be done
with the newly acquired wonder paint. Make
sure to paint copiously over the already
existent paint a little down the side walls to
ensure connection and stay away from all
electrical connections inside.
Of course I also painted the cavity I drilled
in order to replace the dreadful barrel jack as explained
above. Insulate the jack inside!
The arrow points towards one of few places
where I spilled the paint (picture taken after
drying before any further steps. No sweat, it
does not adhere to shiny lacquer.
As expected, hum did not go down, but its higher
frequent components did. The effect is subtle, but
Let me know if any of
this is useful or appeals to you.
Credits: Many threads on modification of
the L-2100 have been sieved through, notably written by
a guy named DavePlaysBass in talkbass
guitar forum and BassesByLeo forum
(several threads), by Femto
and Ken Baker, who maintains BassesByLeo,
all of whom I feel deeply indepted to. Credits also go
to Ulf Schaedla in Germany, probably the best source of
information on pickups and voicing currently
L2K Wiring Mods Rev 4.1, 27-Dec-2117, by
DavePlaysBass@hotmail.com, p.2 Fixing
Bad Designs: Barrel-Style Output Jacks - Hanff
Guitar Repair Jack
Replacement: (how to re-fit a new barrel jack),
by Ken Baker from BassesByLeo Jack Replacement: (how to replace a barrel jack by a conventional
jack), by BluesBassPlayer on BassesByLeo
forum  G&L
Preamp Rev 2.2, 12/28/2017,
by DavePlaysBass@hotmail.com Guitar-Letters: a
wealth of information on pickups and voicing
(in German language), by Ulf
Back To Index Sound Samples The
subsequent recordings have been done using
the following setup and no further
as above, pickups as specified, all controls
full. EB cobalt flat strings.
Pro-Tube IV, direct out
device: Focusrite PC interface into DAW
"inside pair" means _N B_ and "outside" means
N_ _B. Neck single mode inside thus
means _N _ _ and outside N_ _ _ etc.
Yes, more options, more confusion 8-)
On the single mode recordings, you may hear
some hum, but worse, you may hear high
frequent noises to a lesser extent on all
recordings. This comes from the proximity
to the PC, although not necessarily hum. PC´s
and neon lamps are the recording musician´s
worst enemy. Recordings have been done prior
(Names may be
copyrighted by the associated copyright holder, no
association with any of them)
serial / parallel (native)
modes: Neck PU (serial
first, parallel on second phrase)
Note how little difference
there is sonically between serial and
parallel modes when volume-equalized
and when a buffer is behind to avoid
tone sucking. A valid argument to
ditch the serial modes if one wants.
serial / parallel (native) modes:
Both (serial first, parallel on
serial / parallel (native) modes:
(serial first, parallel on second phrase)
modes (cross-mode): Inner Pair Does one of those two
cross into Stingray territory? Guess it does.
modes (cross-mode): Outer
Single coil mode: Neck
Outside (towards neck)
PU Inside (towards