Radio receiver crude triode, was invented in 1906 by Lee De Forest as a more sensitive detector for radio receivers, by adding a third electrode to the thermionic diode detector, the Fleming valve. It was not widely used until its amplifying ability was recognized around 1912. The first tube receivers, invented by De Forest and built by hobbyists until the mid 1920s, used a single Audion which functioned as a grid-leak detector which both rectified and amplified the radio signal. There was uncertainty about the operating principle of the Audion until Edwin Armstrong explained both its amplifying and demodulating functions in a
European Triode Festival European Triode Festival Since 2000 each year the "European Triode Festival" (ETF) has been held in various venues in Europe (the first three events were called "Aarhus Triode Festival" aka "ATF"). The ETF focuses on do-it-yourself audio valve amplifiers using triode vacuum tubes, and brings together high end vacuum tube audiophiles from all over the world (from as far away as Finland and New Zealand). At the festival, participants demonstrate their (all home-built) equipment (analogue/digital/amplifiers/speakers/etc.) and discuss aspects of high-quality vacuum tube sound reproduction. The event is a private venture of in total 300 audio lovers, of which some 120