Audio power amplifier inside the chassis of the main product. The audio amplifier was invented around 1912 by Lee De Forest, made possible by his invention of the first practical amplifying electrical component, the triode vacuum tube (or "valve" in British English) in 1907. The triode was a three terminal device with a control grid that can modulate the flow of electrons from the filament to the plate. The triode vacuum amplifier was used to make the first AM radio. Early audio power amplifiers were based on vacuum tubes and some of these achieved notably high audio quality (e.g., the Williamson amplifier of
William McLellan (American electrical engineer) William McLellan (American electrical engineer) William Howard McLellan (December 1, 1924 – September 30, 2011) was an American electrical engineer, who achieved some fame in 1960 by succeeding at an engineering challenge set by Nobel Prize-winning physicist Richard Feynman. McLellan was born in Casper, Wyoming, grew up in Orland, California, and fought in the Canadian Army in the Second World War. He met his wife Patricia Price in England during the war, and afterwards the couple settled in Pasadena, California, where McLellan attended California Institute of Technology (Caltech). In December 1959, Feynmann offered two challenges relating to nanotechnology at the