Sensibly equivalent¶ to:
The EL84 output pentode was introduced by Mullard in 1954. To demonstrate its use and quality the Mullard applications lab produced an amplifier design. The now classic 5-10 high quality audio amplifier.
The performance figures given here refer to class A operation.
When used as a pair in an ultra-linear push-pull configuration with 43% distributed loading the output could reach 10 W with 0.9 % total harmonic distortion.
With ultra-linear operation the screen grids were connected to taps in the in the output transformer primary winding. The valve operating conditions so produced were intermediate between a triode and a pentode. The operation of the distributed loading was to introduce negative feedback directly within the output stage.
See also UL84 & PL84 produced for designs using AC or DC mains without a mains transformer and a series heater chain. The PL84 was used for TV frame output service.
By clicking the link from the exhibit name above, the full Mullard data-sheet can be downloaded. Warning this is a very large PDF file.
The thin glass tube envelope is 20 mm in diameter and, excluding the B9A base pins, is 70 mm tall.
References: Data-sheet & 1040. Type EL84 was first introduced in 1953. See also 1953 adverts.
Absolute Maximum Operating Conditions¶
Updated January 11, 2018.