Sensibly equivalent¶ to:
The VR40 is the PX25 (PP5/400) in military uniform.
This early audio power triode was one of the first to give a significant output. Five Watts single ended and up to 20 Watts in push pull. With the loudspeakers of the time this was suitable to fill a small hall. With transformers of the period being less efficient than later designs an audio power amplifier using a pair of these valves was a substantial piece of equipment, and heavy.
The ratings given are for class AB1 push pull for a pair of such valves. Under these conditions the grids would require 108 Volts peak to peak to achieve full output.
The balloon envelope has a maximum diameter of 60 mm and excluding the B4 base pins it is 133 mm tall.
References: Data-sheet, 1040 & 1043.
Absolute Maximum Operating Conditions¶
Updated April 03, 2015.