Main Difference – Distortion vs. Overdrive
Distortion and overdrive are two effects employed by guitarists to produce altered versions of sounds originating from their electric guitars. The main difference between distortion and overdrive is that overdrive is produced by a process known as smooth clipping, leading to a less-altered sound while distortion is produced by had clipping, leading to a more altered sound.
What is Overdrive
To produce some of the “heavier” sounds made by electric guitars in blues, rock and metal music, the original sound waves produced by the guitars are often clipped. Clipping is an effect which adds a ceiling to the amplitude of the waveform. As a result of clipping, a waveform breaks down into a collection of its harmonic frequencies.
Frequency refers to the number of times that air molecules vibrate per second to create a sound. To produce higer-pitched sounds, air molecules need to vibrate more times per second, and so higher-pitched sounds are said to have higher frequencies. Harmonic frequencies of a sound refer to other sounds with frequencies which are whole-number multiples of the original frequency. For instance, the C0 note has a frequency of 16.35 Hz. Two times this frequency is 32.70 Hz, and therefore, this is the so-called second harmonic of C0.
Soft clipping produces a waveform which is a combination of odd-order harmonics of the original sound. In a soft-clipped waveform, lower odd-order harmonics (3rd harmonic, 5th harmonic,… etc.) are predominant and the higher odd-order harmonics are present only at very low levels. Overdrive refers to the sound produced by soft clipping. Compared to other clipping methods, overdrive produces a crisper, cleaner sound, often used by blues musicians. For instance, the following guitar solo by Angus Young, the lead guitarist of AC/DC, employs overdrive:
What is Distortion
In contrast to overdrive, distortion employs hard clipping, which produces much flatter waveforms and creates a heavily-altered sound. A waveform that has been subjected to hard clipping has more higher odd-order harmonic components compared to a soft-clipped wave. Distortion also produces sharper, a “heavier” sound, which is characteristic of heavy metal. For instance, Cliff Burton, the late lead guitarist of Metallica, uses distortion:
The image below depicts the difference between soft and hard clipping.
The video below has a good demonstration of the effect of clipping on waveforms, along with a demonstration of the different sounds produced at the end.
Difference Between Distortion and Overdrive
Level of Clipping
Overdrive is produced by soft clipping.
Distortion is produced by hard clipping.
Overdrive produces a sound with the higher odd-order harmonics present at low levels.
Distortion produces a sound with higher odd-order harmonics present at comparatively higher levels.
Overdrive has a “cleaner” sound, often employed by blues artists.
Distortion consists of a “dirtier” sound, often employed by heavy metal artists.
“Diagram showing the difference between soft and hard clipping” by Mikhail Ryazanov (Original version Clipping_compared_to_limiting.svg by Iain) , via (Modified)