Distortion, Overdrive & Fuzz
Three flavors of clipping, all waveshaper transfer curves. Overdrive adds warmth. Distortion adds grit. Fuzz approaches a square wave.
Clipping
When a signal exceeds a threshold, the peaks get cut off. Push an amplifier past its headroom and the waveform tops flatten out. The shape of the cut determines the character of the distortion. A gentle rounding sounds warm, a hard chop sounds aggressive.
The Transfer Curve
A waveshaper maps each input sample to an output value using a curve. A straight diagonal line means "pass through unchanged," clean signal. A gentle S-curve rounds the peaks: overdrive. A sharp step function clips them flat: fuzz. The canvas below the controls shows the active transfer curve so you can see what each type does to the signal.
Odd and Even
Symmetric clipping (same shape on positive and negative halves) adds odd harmonics (3rd, 5th, 7th), producing a cold, buzzy quality. Asymmetric clipping (positive half clips earlier than negative) adds even harmonics (2nd, 4th, 6th), producing the warmth associated with tube amplifiers.
A Short History of Loud
Overdrive originally meant pushing a tube amplifier louder than it was designed to go. Every amplifier has a range where it reproduces the input cleanly, its headroom. Beyond that point, the vacuum tubes can't follow the signal faithfully and start rounding off the peaks. This gentle saturation adds even harmonics that sound warm and musical rather than harsh. Blues and classic rock live here. Marshall and Fender amps from the 1960s turned this "flaw" into a defining sound.
Distortion came from dedicated pedals that clipped the signal harder than a tube amp would naturally. The Boss DS-1 (1978) and ProCo RAT (1978) defined the category: symmetrical clipping with more gain, producing a tighter, more aggressive sound with odd harmonics.
Fuzz is the earliest and most extreme. The Maestro Fuzz-Tone (1962) and Dallas Arbiter Fuzz Face (1966) used transistors to clip the signal so hard it approached a square wave. Jimi Hendrix made fuzz a vocabulary. The "sputtery" quality comes from the transistors' imperfect behavior at low input levels.
Try it: start with "Warm Overdrive" and watch the transfer curve change shape. Switch to "Fuzz Face" and compare the spectrum. Notice how the harmonics multiply as clipping gets harder.