The EL33 audio output valve is the little brother of the EL37 with which it shares pin connections. Mullard describe this valve as a high sensitivity output pentode for use in AC mains equipment. The EL33 could be used in push pull to deliver 8 Watts, but the normal use was in domestic radio receivers as a single ended stage.

The top mica with fingers gripping the shoulder of the envelope. Below the top mica is the mica that holds the tops of the electrodes. The coating obscures the rest of the structure.

The classic envelope is 44 mm in diameter and, excluding the IO base pins, is 109 mm tall.

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

Pin Connections

IO

1

2

3

4

5

6

7

8

m

h

a

g2

g1

nc

h

k