The 6J5G is a single triode is housed within a glass envelope. The electrode assembly is formed on a glass pinch in the traditional style. The anode plates are formed to leave an oval cavity for the grid and cathode. The ST classic envelope is typically 36 mm in diameter and, excluding the octal base pins the is 85 mm tall. Type 6J5G was first introduced in 1936 the L63 was first introduced by Osram in 1938.
The 6J5G is effectively one half of a 6SN7GT. It finds use in many classic and exotic valve amplifiers such as:
Audio Note monoblock amplifier
Audionote Quest mono amplifier
Berning Siegfried amplifier
New Audio Frontiers Absolute MKII preamplifier
Tektron amp & pre amp combo