AES San Francisco 2012
Historical Event H3

Sunday, October 28, 10:45 am — 11:45 am (Room 122)


H3 - Lee de Forest: The Man Who Invented the Amplifier

Mike Adams, San Jose State University - San Jose, CA, USA

After Lee de Forest received his PhD in physics and electricity from Yale University in 1899, he spent the next 30 years turning the 19th Century science he learned into the popular audio media of the 20th century. First he added sound to the wireless telegraph of Marconi and created a radiotelephone system. Next, he invented the triode vacuum tube by adding a control grid to Fleming’s two-element diode tube, creating the three-element vacuum tube used as an audio amplifier and oscillator for radio wave generation. Using his tube and building on the earlier work of Ruhmer and Bell, he created a variable density sound-on-film process, patented it, and began working with fellow inventor Theodore Case. In order to promote and demonstrate his process he made hundreds of short sound films, found theaters for their showing, and issued publicity to gain audiences for his invention. While de Forest did not profit from sound-on-film, it was his earlier invention of the three-element vacuum tube that allowed amplification of audio through loudspeakers for radio and the movies that finally helped create their large public audiences.

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AES - Audio Engineering Society