AMPLIFIER: Speaker Level

The Amplifier is the last stop before the signal reaches the loudspeakers. power amplifiers boorst, or amplify, electronic audio signals sufficiently to move the speakers, They do this by incresasing the gain (the volltage and power) of the signal from line level to speaker level.
Line level is around one volt. Speaker level depends on the type of system. It can range from:

4 to 20 volt or more for stereo sound system
up to 70 volts in a distributed sound system
up to hundreds of volts in large venues

Most amplifies have only a power switch and volume controls, Potentially, the more powerful the amplifier is, the greater the amplification of the signal, and the louder the sound from the speaker