A
guitar amplifier (or
guitar amp) is an
electronic amplifier that amplifies the electrical signal from a
pickup on an
electric guitar,
bass guitar, or
acoustic guitar so that it can produce sound through a
loudspeaker, which is typically housed in a wooden cabinet. A guitar amplifier may be a standalone wood or metal cabinet that contains only the amplifier (and preamplifier) circuits—or it may be a "combo" amplifier, which contains both the amplifier and one or more speakers in a wooden cabinet. Most guitar amplifiers can also modify the instrument's tone by emphasizing or de-emphasizing certain frequencies and adding electronic effects, typically
distortion and
reverb. The input of modern guitar amplifiers is a 1/4" jack, which is fed a signal from a piezoelectric
pickup (usually from an acoustic guitar) or an electro-magnetic one (from an electric guitar).