A guitar amplifier 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.