Sensibly equivalent¶ to:
The EC31 is an audio triode from the late 1940's but is not listed in the 1949 book.
The anode is formed from two plates that are shaped to give a central cylindrical cavity and two cooling fins. The surfaces are blackened to assist radiation. The grid is wound on stout copper rods that have cooling fins attached at the top. This all suggests more than a signal amplifier.
Mullard have specified the EC31 as both a small signal amplifier and also as an low power output stage. With a cathode resistor of 800 Ohms and an anode load of 10,000 Ohms the EC31 will produce 0.5 Watts at 5% distortion.
The detail picture shows the grid cooling mechanism as well as the flattened cylinder of the indirectly heated cathode.
The classic envelope is 45 mm in diameter, and excluding the IO base pins is 96 mm tall.
Absolute Maximum Operating Conditions¶
Updated January 23, 2013.