Audion Audion The Audion was an electronic detecting or amplifying vacuum tube invented by American electrical engineer Lee de Forest in 1906. It was the first triode, consisting of an evacuated glass tube containing three electrodes: a heated filament, a grid, and a plate. It is important in the history of technology because it was the first widely used electronic device which could amplify; a small electrical signal applied to the grid could control a larger current flowing from the filament to plate. The original triode Audion had more residual gas in the tube than later versions and vacuum tubes; the
Valve audio amplifier technical specification to class AB1 push–pull (PP) circuits. Tetrodes and pentodes, sometimes in ultra-linear configuration, with significant negative feedback, are the usual configuration. Some class A push–pull amplifiers are made commercially. Some amplifiers can be switched between classes A and AB; some can be switched into triode mode. Major manufacturers in the PP valve market include: The simplicity of valve amplifiers, especially single-ended designs, makes them viable for home construction. This has some advantages: Point-to-point hand-wiring tends to be used rather than circuit boards in low-volume high-end commercial constructions as well as by hobbyists. This construction style is satisfactory due to ease