Sensibly equivalent¶ to:
The 42 is an audio output pentode, with a low output rating, but when used in push pull a pair could deliver 18.5 Watts in class AB2.
Also on a UX6 base is the 2.5 Volt 2A5 that is electrically equal to the type 42. The Type 6F6 is also electrically identical, but on an IO base.
The Mullard name and Amerty brand - used by Mullard for valves they had imported from America during and just after WWII.
The classic envelope is 45 mm in diameter and, excluding the UX6 base pins, is 100 mm tall.
References: Data-sheet, 1040 & 1043. Type 42 was first introduced in 1936.
Absolute Maximum Operating Conditions¶
Updated January 07, 2017.