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
Virtual Valve Amplifier (amplifier class A), to make only one side conduct at a time (class B), or intermediate (class AB). Class A uses more power for the same output (i.e., is less efficient), can produce less output power from the same devices, and produces lower distortion, than classes AB and B. These devices generally consisted of a 12AU7 medium-mu triode driving a single 6L6GC beam power pentode audio output valve or similar. Its effects are distinctive due to convolution of the non-linearity of the triode interacting with those of the pentode, with both devices operating in class-A mode. The 6L6GC is similar