The Small Rectifier!
The TAD EZ81 / 6CA4 is a small rectifier tube for 6.3V filaments. It is used in smaller amps, such as the Marshall 1974X or the TAD 18W Plexi Kit, Silverstone amps and in various Hammond organ amplifiers. It is a true full power EZ81. Also used in many audio amps and in old tube radios.