The configuration of such a system depends on its intended application. A sound system, or public address system or PA system, typically has microphones, an amplifier, loudspeakers, and controls to mix the signals coming from the various micorphones or other input sources (such as phonograph turntables or tape recorders).
Systems can be as simple as church systems consisting of one microphone for the clergyperson and another for the organist; larger systems have dozens of speakers and draw kilowatts of power in order to create a wall of sound and to fill large arenas such as Madison Square Garden.
Most sound systems contain mixing consoles which enable sound engineers or disc jockeys to adjust the volume for each microphone or input source individually.
The system may also contain an equalizer which allows adjustment of different frequency ranges within an audio signal. Sound effects which might be included in a sound system include reverb, digital echo, or digital time delay.