A Power amp provides power for passive pa speakers and subwoofers Most amplifiers power speakers through the use of multiple transistors, which are cooled by fans when in use. Other types include Switched-mode or class D amps which are controlled by MOSFET / binary switches. Switched-mode amps are usually a lot lighter and more efficient than standard amplifiers. Due to the power drawn and heat generated by amplifiers, thermal, overload, short-circuit and D.C. Protection are often used. Some amplifiers also have low pass or high pass filters and DSP effect processing. Power amps are the driving force behind your PA system, if you need any information on making the right purchase feel free to contact us and we will be happy to help.