That's class...

The final amplifier is the power source of every audio installation. Its job is to convert a small alternating voltage into a powerful signal suitable for driving loudspeakers, with as little distortion as possible. During the years since the invention of electronic audio systems, designers have come up with various approaches to this problem. It all started with Class A... Delivering a large amount of power is not a simple task for an amplifier. Voltage amplification and current amplification are both necessary in order to provide sufficient power to the speakers connected to the amplifier. This is because loudspeakers have an efficiency of only a few percent, which means that several watts are certainly necessary to generate an adequate sound pressure level in a living room. In the case of concerts or outdoor events, quite a bit more is required, and the necessary power can easily amount to several kilowatts.