A guitar amplifier (or guitar amp) is an electronic amplifier designed to amplify the electrical signal of an electric or acoustic guitar so that it will produce sound through a loudspeaker. 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).
