ARP2600 - Fundamentals of Music Technology - Cyborgstudio.com

SECTION ELEVEN: PREAMP, ENVELOPE FOLLOWER, RING MODULATOR - 083DISTORTIONThe preamp has a range of amplitudes of signals that it canhandle. As long as signals stay within this range, the preampwill faithfully amplify signals, and put out what comes in,only louder. (See Figure 11-3)Figure 11-3: A saw wave within thepreamp’s dynamic rangeThe distance from the top of the black rectangle in Figure11-3 to the bottom represents the preamplifier’s dynamicrange or the range of amplitudes which the preamp can accuratelyreproduce. However, it is entirely possible to amplify a signal to the point where the peaks andtroughs of the waveform reach outside the dynamic range. (See Figure 11-4)The preamp cannot handle the highest points of thesewaveforms, and they become clipped off when they reachthe end of the dynamic range. This phenomenon is knownas clipping or distortion. The word distortion has manyuses, but one must think of it as the actual shape of thewaveform being changed or distorted, similarly to the waya funhouse mirror distorts the image of one’s face. Whenthe waveform in Figure 11-4 emerges from the preamp, itwill look like Figure 11-5.Because the actual shape of the wave has changed, so hasthe harmonic content, and thus the waveform’s timbre.Figure 11-4: A saw wave which has exceeded thepreamp circuit’s dynamic rangeThis waveform which was formerly a saw wave will sound more like a square wave. In fact, as theamplitude is increased, the waveform will become more like a square wave. In this sense, the preamplifiercan actually be used to reshape the incoming waveform and turn it into a different wave.DISTORTION: FRIEND OR FOE?To this point, nothing has been said about whether distortionis a good thing or a bad thing. For many years,distortion was considered to be a very bad thing. Distortionin a recording was to be avoided at all costs. Thefaintest crackle was considered to be the sign of a poorrecording. During the late 1950’s and early 1960’s, guitarplayers discovered that if they increased the volumeFigure 11-5: A clipped saw waveof their amplifiers enough, distortion would occur and change the timbre of their guitars. Distortionthus became a popular effect for guitars. In the 1990’s, artists such as Skinny Puppy and Trent Reznorof Nine Inch Nails have taken distortion to a new level, distorting everything from their voices to all ofthe musical instruments in a song.