An audio power amplifier (or power amp) is an electronic amplifier that amplifies low-power electronic audio signals (signals composed primarily of frequencies between 20 - 20 000 Hz, the human range of hearing) to a level that is strong enough for driving loudspeakers and making the signal–whether it is recorded music or a live speech–audible to listeners. It is the final electronic stage in a typical audio playback chain before the signal is sent to the loudspeakers.
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 and microphone signals), equalization, tone controls, mixing different input signals or adding effects. The inputs can be any number of audio sources like record players, CD players, digital audio players and cassette players. Most audio power amplifiers require these low-level inputs to adhere to line levels.
While the input signal to an audio power amplifier may measure only a few hundred microwatts, its output may be a few watts for small consumer electronics devices, such as clock radios, tens or hundreds of watts for a home stereo system, several thousand watts for a nightclub's sound system or tens of thousands of watts for a large rock concert sound reinforcement system. While power amplifiers are available in standalone units, typically aimed at the hi-fi audiophile market and sound reinforcement system professionals, most consumer electronics sound products, such as TVs and car stereos, have power amplifiers integrated inside the chassis of the main product.
