Guitar amplifier

A guitar amplifier (or guitar amp) is an instrument amplifier designed for use with an electric guitar, bass guitar, or acoustic-electric guitar. A guitar amplifier receives an electric guitar's pickup-generated signal and shapes that signal's tone through a preamplifier and amplifies it through a power amplifier; it is then projected through loudspeakers. When the preamp and power amp circuits are combined with one or more loudspeakers in a single enclosure, it is known as a combo. When the preamp and power amp are housed together for use with an external speaker cabinet, 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, high-wattage heads that are usually paired with large external cabinets. The components chosen for an amp's circuit have a significant impact on its tonal character, which can be further sculpted 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 guitar 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 sound. Historically, guitar amplifiers have been designed around vacuum tubes, and to a lesser extent solid-state electronics; digital amplifier modeling is also increasingly common. Guitarists often use external effects pedals to alter their tone before the signal reaches the amplifier.