The evolution of distortion

Professional audio gear is designed to give acceptable noise and minimal distortion at appropriate signal levels. By keeping levels throughout a real signal path around 0dBU, the producer should get good results.

Even so, producers were desperate to keep noise levels down, so they would often intentionally run signals ‘hot’ to increase the signal-to-noise ratio. Most analogue gear breaks up and distorts in a pleasant way, and this characteristic eventually became associated with classic production.

So what is distortion? At its simplest, when a signal is played too loud, the excess is chopped off or ‘clipped’. A sine wave’s smooth top and bottom would be flattened off, making it more like a square wave. This process introduces harmonics, in the same way that ‘squaring off’ a sine wave does.

Analogue distortion comes in a variety of flavours and characters. Early electronic gear used valves (aka tubes), which are associated with producing even and odd harmonics. The 1950s saw valves superseded by the more compact solid-state transistors, which emphasise odd harmonics when distorted, sounding sharper and more aggressive.

Valves aren’t used in consumer electronics anymore, but they still have a place in guitar amps, preamps, and vintage-flavoured effects. Tape lies somewhere between valve and transistor, producing stronger odd harmonics.

While distortion is a technically accurate term, we often use the terms saturation or (over)drive instead, referring to mild and moderate amounts. In music production, ‘distortion’ is usually an aggressive effect – think metal guitars and gabber kick drums.