OPERATION OF CONTROLS AND CONNECTIONS, continued
13 GRAPHIC EQUALIZER
The ACOUSTIC Graphic Equalizer is a unique device for musical instrument amplification similar in
function to a studio equalizer. The Equalizer divides the guitar signal into five sections. Section 1 covers the
50 Hz to 110 Hz range; Section 2 covers the 110 Hz to 220 Hz range; Section 3 covers the 220 Hz to 460
Hz range; Section 4 covers the 700 Hz to 1500 Hz range; and Section 5 covers the 1500 Hz to 2800 Hz
range. These slide controls allow you to boost or cut any of these ranges. The Mid-Range control can be
used to cover the 460 Hz to 700 Hz range. You can shape the response of the amplifier to meet your exact
requirements for a particular song. A flat response (no equalizer boost or cut) is achieved when all 5
controls are centered at "0". There is a special mechanical notch on the control to identify this location so
that this adjustment can be felt without referring to the markings.
How the Graphic Equalizer Works.
Let's take a moment and discuss the typical electric guitar. The actual range of the fundamental notes is
from 84 Hz to about 670 Hz. (The open low E string is about 84 Hz, and the E at the twelfth fret of the first
string is about 670 Hz.) The important harmonic overtones occur from about 180 Hz to about 2200 Hz. It is
the balance between the fundamental notes and their harmonic overtones that determines the type of
sound you get. You probably haven't realized it, but you have been aware of this balance and controlling it
to a limited degree for years. How? If your guitar has two pickups, you use the front pickup when you want
fundamentals and heavy bottom. You use the back pickup when you want more overtones. Using your
fingers gives you more fundamentals; using a pick gives you more overtones.
The Graphic Equalizer is a logical extension of this fundamental-to-harmonic balance control. With all this
in mind, let's look at the Graphic Equalizer and see how it applies.
Section 1 (50 Hz to 110 Hz) covers all the notes on the E (sixth) string and about half of the notes on the A
string. It also covers the range about one-half octave below the low E in case you are into Modal or slack
tunings.
Section 2 (110 Hz to 220 Hz) covers all the notes on the D and G strings as well as half the notes on the B
string.
Section 3 (220 Hz to 460 Hz) covers some of the notes on the B string as well as most of the notes on the
High E string. Use the mid-range control for the highest notes of the high E string.
Section 4 (700 Hz to 1500 Hz)covers the second harmonics of the E string.
Section 5 (1500 Hz to 2800 Hz) covers the second harmonics of the high strings and higher harmonics on
the middle strings.
Continues after diagram ….
