An audio power amplifier is an electronic amplifier that amplifies low-power audio signals (signals composed primarily of frequencies between 20 - 20,000 Hz, the human range of hearing) to a level suitable for driving loudspeakers. It is the final electronic stage in a typical audio playback chain.
The preceding stages in such a chain are low power audio amplifiers which perform tasks like pre-amplification (this is particularly associated with record turntable signals), equalization, tone controls, mixing/effects, or audio sources like record players, CD players, MP3 players, midia players and cassette players.
