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 Vienna valve trombone Vienna valve trombones use Vienna Valves which were one of the earliest valve systems used in wind instruments. These valves were first publicly reported in 1815 and valved trombones were first introduced in the late 1830s. The Vienna valve was invented in Leipzig in 1821 by Sattler, predating the Perinet valve and rotary valve used in France and Germany (and in all French horns). The Vienna Valves (or Double Valves) have two short parallel pistons connected at the bottom by a bar that is moved by a long rod or linkage connected to the spring-loaded finger plate.