The EL34 was the 1952 successor to the very successful EL37 with which it shares a high value of mutual conductance of 11.0 mA/V allied to a maximal anode dissipation level of 25W with a sub 1.5% distortion level possible. The EL37 was of pinch construction whereas for the EL34 mullard used the pressed glass foot construction employed on the B9A and B7G miniature valves for this IO based device.
When used in push-pull ultra linear configuration is capable of excellent results and low distortion. The definitive circuits for these valves was given by Mullard's own design labs in the publication Circuits for Audio Amplifiers. Having a tall form glass tubular envelope of approximately 35mm diameter and 100mm length this is a compact punch packing output pentode which found use in many classic valve guitar amplifiers, classic valve hifi amplifiers from Leak, Concordant, Dynaco, Tannoy, Decca, Pye, Radford and Rogers to name but a few! Some current exotica using the EL34 is listed below:-