WR50

WR50 is direct-heated type thorium tungsten cathode triode, can be used as class A1 and AB1 amplification. 

Typical operating parameter 
Heater voltage                  7.5 V
Heater current                   1.25A
Ua                            350V

Grid voltage                     -63 V
Ia                              45 Ma
Internal resistance                 4.1K
Amplification coefficient            3.8
Output power                     2.4W