Control grid Control grid The control grid is an electrode used in amplifying thermionic valves (vacuum tubes) such as the triode, tetrode and pentode, used to control the flow of electrons from the cathode to the anode (plate) electrode. The control grid usually consists of a cylindrical screen or helix of fine wire surrounding the cathode, and is surrounded in turn by the anode. The control grid was invented by Lee De Forest, who in 1906 added a grid to the Fleming valve (thermionic diode) to create the first amplifying vacuum tube, the Audion (triode). In a valve, the hot cathode emits
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