Amplifiers are the device that the sound of the guitar comes out of, this piece of equipment is essential to play electric guitar and is a necessity to most types of music.

A guitar amplifier (or amp) is an electronic device  that strengthens the weak electrical signal from a pickup on an electric guitar, or bass guitar so that it can produce sound through one or more loudspeakers, which are typically housed in a cabinet mad of wood. A guitar amplifier may be a standalone wood or metal cabinet that contains only the power amplifier circuits, requiring the use of a separate speaker cabinet–or it may be a "combo" amplifier, which contains both the amplifier and one or more speakers in a wooden cabinet. There is a wide range of sizes and power ratings for guitar amplifiers, from small, lightweight "practice amplifiers" with a single 6" speaker to heavy combo amps with four 10” or four 12" speakers and a powerful amplifier, which are loud enough to use in a nightclub or bar performance.

 

Guitar amplifiers can also modify the instrument's tone by focusing certain frequencies, using  controls, and by adding electronic effects; distortion (also called "overdrive") and reverb are commonly available as built-in features. The input of modern guitar amplifiers is a 1/4" jack, which is fed a signal from an magnetic pickup (from an electric guitar) using a cord, or a wireless transmitter. For electric guitar players, their choice of guitar amp and the settings they use on the amplifier are a key part of their signature tone or sound. Some guitar players are longtime users of a specific amp brand or model. Guitarists may also use external effects pedals to alter the sound of their tone before the signal reaches the amplifier.