Sound Reinforcement Amplifiers
Power amplifiers provide the grunt behind sound reinforcement and public address systems. Small systems can get away with a single amplifier but any sizeable system will need multiple amplifiers.
Smaller systems often have combo units where the amp, mixer and other controls are built into the same unit. Large systems use much more simple units which only serve to increase the power level of the signal. These units are usually referred to as power amplifiers.
Most power amps have few (if any) controls — typically an on/off switch and level controls for each channel (usually turned all the way up). Since all signal processing is done by other equipment, there really is no need to have any controls on the amps.
Power amps are typically rated at a minimum of 800 watts — large systems use amplifiers rated much higher.
When using a power amp, make sure the level is turned right down before turning it on. Under normal circumstances you will then turn the level right up to the maximum setting — the overall volume level is controlled from the mixing desk and other devices. When you have finished, turn the level right down before turning it off.