Gain

The amount by which a circuit multiplies the signal level passing through it, and on guitar amps the control that sets how hard the later stages are driven.

It is worth separating the two meanings because they behave differently: gain multiplies, while a level or volume control attenuates. On a valve amplifier the gain knob decides how much the preamp pushes the output section, so it changes the amount of distortion and compression as much as the loudness. On a pedal, gain usually means the same thing, which is why the same setting into two different amplifiers produces two different amounts of dirt.

Example: a pedal with its gain low and level high will push an amplifier into distortion without adding more of its own.

Gain

See also