BUILD IT YOURSELF
In this day and age of highfalutin
audio electronics, it is somewhat
surprising that most electric guitars
sport tone controls that weren't
cutting edge even half a century ago.
A new guitar still has a non-zero
probability of sounding pretty "blah"
no matter how good the pickups are.
It may have a weak low end
response, or perhaps the treble
setting is dull. Maybe it doesn't offer
much variation in tonal quality
overall. This article describes a
retrofit you can make that will give
your guitar the controls it deserves.
Even the most plain Jane instrument
leaps alive with a full range of bass,
mid, and high end color. Best of all,
it does it quietly; noise, hum and hiss
are simply not an issue thanks to
several tricks explained here.
HOTROD YOUR ELECTRIC
GUITAR WITH ACTIVE TONE
October 2014 29
Post comments on this article
and find any associated files
and/or downloads at www.
By Thomas Henry
The Problem with Passive
To better understand the value of what’s coming up, let’s see how
things are handled in a stock unit. The controls on a typical two-pickup
electric guitar are often passive in nature (Figure 1). The capacitors shunt
higher frequencies to ground, while their series
potentiometers vary the amount of this action. Clearly,
the most you could hope for with such a simple affair
is the ability to gently roll off the treble response at
about – 6 dB/octave. The effect is so feeble that many
guitarists simply leave the tone controls at full
resistance and alter the sound on their amplifiers.
Completing the circuit, two additional potentiometers
directly parallel the pickups, providing control over the
volume. In general, passive tone controls like this have
a low input impedance which can load down the
pickups appreciably. This typically results in an
attenuation of the higher frequencies, yielding a sound
lacking sparkle or brilliance. To lessen this effect, 500K
potentiometers (a fairly high value indeed) are used
throughout. This then raises the output impedance of
the circuit, giving less than optimal results when ■ FIGURE 1. Passive controls on a typical electric guitar.