Amplifier by their physical placement in the signal chain; a preamplifier may precede other signal processing stages, for example. The first practical electrical device which could amplify was the triode vacuum tube, invented in 1906 by Lee De Forest, which led to the first amplifiers around 1912. Today most amplifiers use transistors. The first practical device that could amplify was the triode vacuum tube, invented in 1906 by Lee De Forest, which led to the first amplifiers around 1912. Vacuum tubes were used in almost all amplifiers until the 1960s–1970s when the transistor, invented in 1947, replaced them. Today, most amplifiers
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