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The EL33 audio output valve could be used in push pull to deliver 8 Watts, but the normal use was in domestic radio receivers as a single ended output stage where the volume was adequate for most living rooms.

This Tungsram exhibit was imported to the UK and is marked as foreign.

The silver gettering at the top and the grey internal coating hide the inner construction. It is interesting that there is some red paint around the top of the base cap. The Mullard EBL31 et al has red paint around the base of the envelope to match the red metallic paint on those E series valves that required screening. A rebranded Philips valve?

The classic envelope is 44 mm in diameter and, excluding the IO base pins, is 106 mm tall.

References: Data-sheet, ¹⁰⁴⁰ & ¹⁰⁴³. Type EL33 was first introduced in 1938. See also 1938 adverts.

Pin Connections

Absolute Maximum Operating Conditions^¶

Thanks to Frank Philipse for supplying the above PDF datasheet.