The PL33 is a high sensitivity audio output pentode designed for universal equipment with 300 mA heater chains. Mullard specify this valve for up to nine watts anode dissipation. In addition to single ended audio applications the PL33 was designed with television frame output service in mind.
The first set of parameters is for single ended service and the second for a pair of valves operated in class A push pull. The grid voltage in the second set of figures is the peak to peak input voltage.
In this exhibit the top shape of the cathode tube is clear. The diameter is reduced before it is held in the top mica.
The oval anode with side flanges for the fixing stitches and support rods.
The classic envelope is 44 mm in diameter and, excluding the IO base pins, is 109 mm tall.
