Under the hood of
a Fender Esquire:
The passive circuitry
offers many options
for tweaking your
sound.Last month, we began exploring mods for
the Fender Esquire—a guitar that’s near
and dear to my heart [“Esquire Mods, Part 1,”June 2012]. Now let’s press forward and look at
even more ways we can customize its circuitry.
Previously, we saw that while retaining
the stock values of the three capacitors
and one resistor Fender used in early-’50s
Esquires, we could alter the guitar’s sound
by trying different brands of these components
made from different materials.
But you can also go one step further and
change the values of the parts used in the
resistor/capacitor network (aka “RC network”)
itself. To do this, you’ll need to understand
what the individual parts are doing. One of
the three caps is very easy to understand—it’s
the one connected to the tone pot. As you
might guess, this is our standard tone cap, and
it’s only engaged in switching position #2,
when the pickup is running through the volume
and tone controls of the Esquire’s circuit.
You can use a smaller value for a “lighter”
tone control (i.e., one that provides less
treble roll-off ) and/or use a different type
of cap. Besides an Orange Drop cap, I also
like a paper-in-oil cap or a new-old-stock
(NOS) ceramic disc in this place. Values
from 3300 pF up to 0.1 μF will work—it’s
simply a matter of personal preference.
The two other caps and the resistor are
directly connected to the 3-way pickup
selector switch and these work together to
serve three different functions:
1. Reduce the volume of the bass tone
to approximately 50 percent to avoid
overloading the guitar amp.
2. Limit the frequency response at
approximately 500 Hz.
3. Shift the resonance peak to approximately
+2 dB at 500 Hz.
In layman’s terms, this is very similar to
having a fully closed tone control, but without
a variable pot to dial in different shades
of tone. The fixed cap value has a twist to
make it sound closer to a bass guitar.
Personally, I think this is really one of Leo’s
genius ideas, and one that I’m sure he figured
out by trial and error. There are only three
parts, yet there’s a lot more going on here
than meets the eye. The chosen values are
perfect for emulating the tone of an acoustic
bass with your guitar. Remember, the Esquire
circuit was developed before Leo invented the
P bass, so the sound of an old “doghouse”
upright bass was the tone Leo had in mind.
So what can you do to mod these parts?
Let’s start with the cap that’s connected to
the 3-way switch on one side, and to the
case (ground) of the volume pot on the other
side. This cap, together with the second cap
that’s connected to the resistor, is creating a
so-called “capacitive voltage divider,” attenuating
the signal. The ratio of these two caps
determines the factor of the attenuation.
With two 0.05 μF caps, we’re attenuating the
signal to about 50 percent of the original.
Mod possibility #1: If you make this
cap smaller, the signal will be louder and
vice versa. NOS ceramic caps, which usually
offer tons of harmonic overtones, sound
very good in this position.
Now let’s have a look at the second 0.05
μF cap, the one connected to the 3.3k resistor
on one side and the 3-way switch on
the other side. By influencing the resonance
peak and the resonance frequency, this
combination makes an Esquire sound more
like a bass guitar than merely a fully closed
guitar tone pot. There are complicated
electrical dependencies at work here, but I
won’t bore you with the equations.
Which brings us to ...
Mod possibility #2: If you make the
resistor smaller, the resonance peak will
walk up from upright bass to short-scale
bass territory, and proceed on to baritone
guitar up to the normal guitar ballpark. If
you make this resistor larger, the resonance
peak will go down to 5-string and further
on into 6-string bass territory.
Mod possibility #3: The cap connected
to the resistor determines the resonant frequency,
or—in simple terms—how dark the
tone will be. Making this cap smaller will add
more brightness to the tone and vice versa.
So as you see, even with only one pickup,
the Esquire offers many possibilities for
you to customize your personal tone. Next
month, we’ll continue with more Esquire
modifications and take a close look at the
“Eldred wiring” scheme, so stay tuned.
Dirk Wacker lives in
Germany and is fascinated
by anything related to old
Fender guitars and amps.
He plays country, rockabilly,
and surf music in two
bands, works regularly as a
session musician for a local studio, and writes
for several guitar mags. He’s also a hardcore
guitar and amp DIY-er who runs an extensive
website—
singlecoil.com—on the subject.