EF86

EF86
Four EF86-type tubes
Classification	Pentode
Service	Audio frequency
Cathode
Cathode type	Indirectly heated
Filament voltage:	6.3 V RMS or dc
Filament current	200 mA
Anode
Max dissipation Watts	1 W
Max current	6 mA
Socket connections
B9A
Typical class-A amplifier operation
Amplification factor	185 (45dB)
Screen voltage	200 V

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. Unlike many pentodes, it was designed specifically for audio applications, with low noise and low microphony claimed advantages, although a rubber-mounted vibration-resistant base was still recommended.^[2] It has a much higher stage gain than any triode, which makes it susceptible to microphony. The EF86 was used in many preamplifier designs during the last decades of vacuum tube hi-fi development. An industrial tube variant is known as 6267. In the former Soviet Union a variant was also produced as type 6Zh32P (Russian: 6Ж32П.) As of 2012^[update] EF86s were being produced in Russia in two versions under the Electro-Harmonix brand and in the Slovak Republic as JJ Electronic (formerly Tesla).