Audio circuits had been the first electronics circuits with a practical conception, the necessity to communicate and transmit sounds with higher levels and large distances generates many circuits, since the simple amplifier to the most sophisticated electronic circuit of transmission and captation of long-distance sounds.

Power RMS or average quadratic value or rms (root mean square)

Power PMPO - the level of peak of instantaneous exit relates - Peak Momentary Output Performance.

An audio amplifier is a electronics amplifier , amplifies frequency signals between the 20 Hertz to 20,000 hertz.

The input signal in amplifier can be only some micron-watts output can be ten, one hundred or thousand of watts.