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.
The anode face view. The control grid has heat radiating fins at the tops of the copper supports.
Side view with the details hidden by the internal coating.
The top of the valve: the windings of the outer two grids can be seen and the cathode tube has a reduced diameter at the top where it is held by the first of the two top mica sheets.
The classic envelope is 44 mm in diameter and, excluding the IO base pins, is 109 mm tall.
