The EF86 is the standard early stage audio pre-amplifier valve. This exhibit was made by Mullard who designed the EF86 as a development of the EF40. Mullard describe the EF86 as a low noise pentode intended for use as a RC coupled AF voltage amplifier, particularly in the early stages of high gain audio amplifiers, microphone pre-amplifiers and magnetic tape recorders.This exhibit has a plain bright outer screen whereas most EF86 examples have a perforated electrostatic outer screen.![](../pics/abh0187a.jpg)
The hole in the screen reveals the grid axis and all three wire grids.![](../pics/abh0187b.jpg)
The bright screenThe thin glass tube envelope is 20 mm in diameter and, excluding the B9A base pins, is 48 mm tall.Reference: Data-sheet & 1040. Type EF86 was first introduced in 1953. See also 1953 adverts. |