Below pages from the Mullard "Audio Valves" booklet of April 1954 relating to the ECC82 double triode - specifications and characteristic curves. As is well known, AC30/6s used just one: V8, for the modulation of the Vib/Trem circuit.

Detail of the JMI circuit diagram OS/065 for the AC30/6, originally drawn up in April 1960. The ECC82 (12AU7) is the amplitutude modulator valve for the Vib/Trem circuit.

It is worth noting that an ECC82 was used for the same function and in the preamp of the AC30/4, also V8. Altdhough the preamp of the single speaker AC/30 of 1959-1960 only used ECC83s, the Vibravox unit, available from late 1957 separately or built-in, naturally had an ECC82 as modulator. On the Vibravox unit, see this page. Notes on the ECC83 can be found here.

From 1959 to mid 1962, Mullards were the norm. From late 1962 to 1965 one finds both Brimars and Mullards: the former normally fitted by Burndept, which started producing chassis for JMI in the autumn of 1962 (the Brimar factory was not far from the Burndept Works); the latter fitted by Westrex. In 1965 Westrex's contract came to an end. From 1965-1968 Burndept used both Brimar and Mullard.

Notes will be added shortly on the date codes of Brimar and Mullard valves.

Mullard's booklets were updated periodically to include details of new valves. In late 1954 the GZ34 was introduced, and in 1957-1958 production of the EL34 began at the Blackburn factory. JMI will have had multiple copies of the various issues.

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