How Do Guitar Amplifiers Work?

Basics

As its name implies, a guitar amplifier is designed to increase (amplify) the sounds produced by a musical instrument. This is a necessary element in playing a strictly electric instrument (as opposed to an acoustic or acoustic-electric instrument) because the normally solid bodies of electric guitars do not create the same natural amplification provided by the resonant cavity of an acoustic or acoustic-electric guitar (an unplugged electric guitar produces very little sound).

Pickup

The pickup is a transducer used in an electrical guitar to change vibrations from its strings into an electric signal. Using magnetic disturbance, the pickup's coil is vibrated, and the output of this signal travels though a cord to the amplifier (specifically to the preamplifier).

Preamplifier

The preamplifier provides simple amplification (sometimes merely through volume control) of the signals received from the guitar through a cord. The preamp levels out the sound and is also the point at which effects (reverb, chorus, etc.) are added into the sound. In many amplifiers, the preamp consists of a series of vacuum tubes.

Power Amp

The power amplifier delivers the amplified signal from the preamplifier to the amp's speakers as sound. Though once commonly made of vacuum tubes (as are preamplifiers), power amps are today more commonly constructed of semi-conductors (called solid-state amplifiers). Nevertheless, various musicians prefer different configurations of tube and solid-state amplification for their various tonic qualities.

Types

A combination amplifier is one that includes in its main body the speakers to which the amp routes its signal. An "amp head" is only an amplifier and must be attached to speakers in order to produce sound.