Experiment 30: Fuzz

Chapter Experiment 30: Fuzz

Make Electronics Book Learning by Discovery
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Make Electronics Book Learning by Discovery

  • What Next?257Experiment 30: FuzzExperiment 30: FuzzLet’s try one more variation on the circuit in 261,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.BAckgroundClippingIn 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.