A power amplifier is an electronic device that increases the amplitude of an audio signal to drive a loudspeaker or other load. It takes a low-level audio signal from a preamplifier and increases its power to drive the speakers with enough energy to produce sound. Power amplifiers come in various designs and classes, ranging from tube to solid-state, and can be used for various applications, including music playback, live sound reinforcement, and home theater systems. A power amplifier's quality is determined by its power output, frequency response, distortion level, and efficiency, among other factors.