Type 6J7 was originally designed as a detector, however, its linear characteristic and good internal shielding (cf. 6Q7G) made it a natural choice for audio.It was for two decades the international standard valve for audio amplifier input stages and audio systems generally. The Mullard-Philips type EF37A, for many years the standard British low-noise audio pentode, is really a 6J7G under another name.This American made valve carries the old UK military stores code of 110E/105 and was thus made for use in the UK.
Further round the base cap is the crown and AM logo of the Air Ministry. This was a valve for the RAF.
The screening cylinder hides the inner pentode structure.The classic envelope is 38 mm in diameter and, excluding the IO base pins, is 96 mm tall.References: Private communication & data-sheet. Type 6J7G was first introduced in 1936. See also 1936 adverts. |
