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
Owen Williams (engineer) excelled in mathematics. He was apprenticed to the Electrical Tramways Co. in London in 1907 and at the same time did an engineering degree at the University of London. In 1912 Williams assumed a position as engineer and designer with the Trussed Concrete Company. Seven years later, he started his own consulting firm, Williams Concrete Structures. He was then appointed chief consulting civil engineer to the British Empire Exhibition which included the old Wembley Stadium. The commission also included the Palace of Industry building in Brent, the first building in the United Kingdom to use concrete as the exterior. The