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
Vienna valve trombone The Vienna system was in common use in Germany on all kinds of instruments including trumpets up to 1850. Adolph Sax invented instruments with 6 independent valves 3 for each hand, but only the most dexterous musicians were able to play them. The valve trombone has definite advantages over the more common slide trombone, such as taking up less room in a seated orchestra. Verdi, for example, composed passages that would have been impossible on a normal slide trombone. For illustrations of a Vienna valve trombone c.1850, see: Vienna valve trombone Vienna valve trombones use Vienna Valves which were one