Guitar amplifier

A guitar amplifier (or amp) is an instrument amplifier designed for use with an electric guitar, bass guitar, or acoustic guitar. When a guitar amplifier's preamplifier and power amplifier circuits are combined with a speaker cabinet and one or more loudspeakers, it is known as a combo. When the circuits are housed in a dedicated enclosure, it is known as a head. There is a wide range of sizes and power ratings for guitar amplifiers, from small, low-wattage practice combos to heavy, 100-watt (or greater) heads that are often paired with large external cabinets. In addition to amplifying the guitar's signal, amps typically modify its tone by emphasizing or de-emphasizing certain frequencies using equalizer controls and through producing distortion (also known as overdrive). Reverb is a common built-in effect.

Commercially available amplifiers were first released in 1928 but did not become widely used until the introduction of mass-produced solid-body electric guitars and basses in the 1950s. Notable brands include Fender, Marshall, Vox, and Mesa/Boogie. For players, their choice of amp and the settings they use are a key part of their tone or sound. Historically, guitar amplifiers have been designed around vacuum tubes, but solid-state technology and digital signal processing have also been used. Guitarists often use external effects pedals to alter their tone before the signal reaches the amplifier.