There are two types of PA amplifier. The first is purely a power amplifier producing an amount of watts and is generally connected at one end to a mixing desk and at the other end to one or more speakers. On professional systems there may be the requirement to have separate power amplifiers for each frequency range, so for example there may be 1000w for the bass speakers, 800w for the midrange drivers and 500w for the high frequency compression drivers.
The other type of PA amplifier is known as a "Mixer-Amp" where the amplifier has built-in mixing capabilities and where a series of channels separates each sound source. The mixer amp is capable of processing each input channel by adding EQ and other effects to each sound source and commonly has an additional send and return input for auxiliary effects.
