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Distortion/ Overdrive

Here is a past exam question and the associated mark scheme.

Question:

Distortion is used on the electric guitar to modify the tone and increase sustain. Describe

what distortion is. Describe the various ways that distortion has been added to the electric

guitar from the 1950s to the present day.

Answer:

In the context of electric guitar, distortion is created by clipping/ cutting off of the

waveform.

Distortion can occur by overloading an amplifier/ pushing an amplifier to output more that

it is capable.

The resulting signal has more power. The resulting signal has more harmonics/ partials

giving a brighter/ harsher tone.

IMD - Amplitude modulation of signals containing 2 or more frequencies with non-

linearities.

Voltage

Time

7/28/2019 Distortion: Overdrive

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In early days distortion was often added to a guitar by a valve falling out/ being damaged

or cutting holes in the speaker cone. Some plugged in their guitar directly into the mixing

desk and turned up the channel gain.

Some artists chained amps together to achieve a distorted tone. In the 1960s, Jim

Marshall modified amplifier circuitry to make distortion easier to achieve.

Distortion is sometimes called fuzz/ overdrive/ clipping. Fuzz is a more distorted/ higher

driven sound than overdrive.

Typical distortion controls:

Gain - A master volume knob is used to compensate for the increased gain/ control

clean-distorted volume difference.

Valve/ tube distortion:

As the amplifier approaches its maximum the increase in signal is non-linear. This results

in the peaks in the waveform looking flattened/ rounded. This produces soft clipping. The

distortion tone is warm/ less harsh.

Transistor distortion gives a harsher distortion because hard clipping occurs immediately

when the maximum output is exceeded.