Vox AC30/4 - Mullard EF86 preamp valve

1960-1961

Below pages from the Mullard "Audio Valves" booklet of April 1954 relating to the EF86 pentode - specifications and characteristic curves. The EF86 was an integral part of the preamp (V1, Normal Channel) of the Vox AC30/4 - black panel, four inputs, TV Front and split front format, 1960-1961. The circuit diagram is available . In relation to the ECC82 and ECC83 (double triodes and common as preamp valves), the EF86 has a relatively high gain. In terms of sound, a sparkling brilliance, its only drawback being mechanical - a greater than average susceptibility to microphony and sensitivity to vibration. The corresponding valve in the AC30/6 is an , less shimmering sonically, but more robust mechanically.

A detail of JMI circuit diagram OA/032 for the AC30/4 showing the position of the EF86.

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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