The audio amplifier was invented in 1909 by Lee De Forest when he discovered a triode vacuum tube. The three terminals of the device with the control box can modulate the flow of electrons from the filament to the plate. The triode vacuum amplifier is used to create the first AM radio. , Williamson amplifiers from 1947 -9). Most modern audio amplifiers are based on solidstate devices (transistors such as BJTs, FETs and MOSFETs), but there are still some who prefer amplifiers with a combination, because the valve sound is considered 'warm'.

Image category:
- amplifier circuit diagram