El84 / 6bq5

The EL84 (European designation - known as the 6BQ5 in North America) is a vacuum tube (a.k.a. valve) of the power pentode type. It has a 9 pin miniature base and is found mainly in the final output stages of amplification circuits, most commonly now in guitar amplifiers, but originally in radios and many other devices of the pre-transistor era.

Equivalents or near equivalent:
6P14P (Cyrillic: 6П14П) made in the USSR.

External links:
EL84/6BQ5 datasheet
EL84 (TDSL)

Amplifiers using EL84
Baby Huey PP EL84 amplifier
Red Light District | PP Pentode
El Cheapo | PP Triode with 6AQ5, can be made with EL84
RH84 | SE Pentode