Valve of the month - EF95

6J1

Happy New Year, valve buffs.
The EF95 / 6AK5 / 6J1 is a 7 pin pentode that is physically small and the electrode assembly is no more than a 10 mm cube.
Although designed for VHF amplification, the tube has found some use in many audio applications such as a microphone preamplifier,  and in guitar effects stompboxes, as well as hifi applications. Due to its low cost, the 6AK5 was used in some types of weather balloon payloads, in the 1960s and 70s.