The Early Mullard Naming Convention

The Type No. AC044 merits comment because it is so frequently quoted as ACO44, even in some later official Mullard publications.

According to the nomenclature used by Mullard when the AC044 was introduced:

AC---	Directly-heated filament designed for AC operation
--04-	The nominal mu value ie. 4
----4	Indicates the filament voltage ie. 4

Further examples

AC042	Same as AC044 but with 2-Volt filament
AC064	Similar to original AC044 but with mu = 6
AC084	Similar but 400-Volt anode rating and mu = 8
AC104	Similar to original AC044 but mu = 10

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