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Often, but not always, in the European valve naming scheme for pentodes an even number indicated a sharp-cutoff device while odd indicated remote-cutoff; the EF37 was an exception to this general trend, perhaps due to its history as an update to the EF36 ("The Mullard EF36, EF37 and EF37A" at the National Valve Museum).
EF50. In the field of electronics, the EF50 is an early all-glass wideband remote cutoff pentode designed in 1938 by Philips.It was a landmark in the development of vacuum tube technology, departing from construction techniques that were largely unchanged from light bulb designs. [1]
Remote cutoff [ edit ] A vacuum tube (such as a pentode , but also sometimes triodes , hexodes, heptodes and so on ) with its control grid given a helix with a variable pitch can be made to operate with more negative grid voltages, with reduced amplification , before it is completely cut off (i.e. yielding no significant output).
EF39/6K7 – Remote-cutoff RF pentode for use as an IF amplifier or as a superheterodyne mixer (1st detector). Also used in test equipment. Also used in test equipment. EF4, EF22 and EF41/6CJ5 with an Octal base with control grid on top-cap
The control grid is an electrode used in amplifying thermionic valves (vacuum tubes) such as the triode, tetrode and pentode, used to control the flow of electrons from the cathode to the anode (plate) electrode. The control grid usually consists of a cylindrical screen or helix of fine wire surrounding the cathode, and is surrounded in turn by ...
For signal pentodes, an odd numerical identifier most often identified a variable transconductance (remote-cutoff) valve whereas an even number identified a 'high slope' (sharp-cutoff) valve. For power pentodes and triode-pentode combinations, even numbers usually indicate linear (audio power amplifier) devices while odd numbers were more ...
The EF86 [1] is a high transconductance sharp cutoff pentode vacuum tube with Noval (B9A) base for audio-frequency applications. It was introduced by the Mullard company in 1953 [2] and was produced by Philips, Mullard, Telefunken, Valvo, and GEC among others. It is very similar electrically to the octal base EF37A and the Rimlock base EF40.
P (Russian: П) – Output pentode or beam tetrode. J (Russian: Ж) – Sharp-cutoff pentode (also transliterated zh, sh or j). K (Russian: К) – Variable-mu / remote-cutoff pentode. R (Russian: Р) – Double pentode or double tetrode. G (Russian: Г) – Combined triode-diode. B (Russian: Б) – Combined diode-pentode.