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What Next? 257

Experiment 30: Fuzz

Experiment 30: Fuzz

Let’s try one more variation on the circuit in Experiment 28. This will demon-
strate another fundamental audio attribute: distortion.

You will need:

• One more 100K potentiometer.


• Generic NPN transistors: 2N2222 or similar. Quantity: 2.


• Various resistors and capacitors.

BAckground

Clipping

In the early days of “hi-fi” sound, engineers labored mightily

to perfect the process of sound reproduction. They wanted

the waveform at the output end of the amplifier to look

identical with the waveform at the input end, the only dif-

ference being that it should be bigger, so that it would be

powerful enough to drive loudspeakers. Even a very slight

distortion of the waveform was unacceptable.

Little did they realize that their beautifully designed tube

amplifiers would be abused by a new generation of rock

guitarists whose intention was to create as much distortion

as possible.

The most common form of waveform abuse is techni-

cally known as “clipping.” If you push a vacuum tube or a

transistor to amplify a sine wave beyond the component’s

capabilities, it “clips” the top and bottom of the curve. This

makes it look more like a square wave, and as I explained in

the section on waveforms, a square wave has a harsh, buzz-

ing quality. For rock guitarists trying to add an edge to their

music, the harshness is actually a desirable feature.

Figure 5-53. This Vox Wow-Fuzz pedal was one of the early

stomp boxes, which deliberately induced the kind of distortion

that audio engineers had been trying to get rid of for decades.

The first gadget to offer this on a commercial basis was

known as a “fuzz box,” which deliberately clipped the input

signal. An early fuzz box is shown in Figure 5-53. The clip-

ping of a sine wave is shown in Figure 5-54.

Figure 5-54. When a sinewave (top) is passed through an

amplifier which is turned up beyond the limit of its components

(shown as dashed lines, center), the amplifier chops the wave

(bottom) in a process known as “clipping.” The result is close

to a square wave and is the basic principle of a fuzz box com-

monly used to create a harsh guitar sound.