6N2P
The 6N2P, (Russian: 6Н2П), also sometimes spelled in English "6H2Pi", is a miniature 9-pin dual
The 6N2P is not a pin-compatible replacement for the 12AX7 - an adapter (Or rewiring the valve socket) is required. The amplification factor of 6N2P is 98 which is marginally lesser than 12AX7, its higher heater current draw is similar to a 5751. The Chinese 6N4 (whose military issued variant is known by the designation 6N4-J) which is a pin-compatible replacement for the 12AX7 but has an amplification factor of 97.5 is the closest equivalent to the 6N2P.
In the 1970s an improved and more rugged version of the 6N2 was introduced, designated 6N2P-EV (Russian: 6Н2П-ЕВ). They also introduced a long life variant of the 6N2P-EV, designated 6N2P-ER (Russian: 6Н2П-ЕP). While the 6N2P-EV had a rated lifespan of ≥ 5,000 hours, the 6N2P-ER had a rated lifespan of ≥ 10,000 hours.
In the late 1980s Voskhod Sunrise produced a 12AX7 variant derived from the 6N2P-EV, under the designation 12AX7VKA. The Voskhod Sunrise 12AX7VKA tube used a larger bottle than other 12AX7s and did not fit in most Chinese shield bases. However, it did fit in most NOS and Korean made shield bases. Currently, a re-issue of the Voskhod Sunrise 12AX7VKA albeit with a smaller normal 12AX7 sized glass bottle is being produced by Sovtek, under the designation 12AX7WA.
A
In the 1990s a (now extinct) line of "Red Bear"