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
Christopher Rose (electrical engineer) Christopher Rose (electrical engineer) Christopher Rose (born January 9, 1957) is a professor of engineering and associate dean of the faculty at Brown University in Rhode Island and a founding member of WINLAB at Rutgers University in New Jersey. He was educated at the Massachusetts Institute of Technology; SB'79, SM'81, Ph.D'85 all in Course VI (Electrical Engineering and Computer Science). On September 2, 2004, an article by Christopher Rose and Gregory Wright, titled "Inscribed matter as an energy-efficient means of communication with an extraterrestrial civilization", appeared on the cover of "Nature" with the headline "Dear ET...". The article argued that