12AX7

12AX7 is a miniature dual triode vacuum tube of high gain. It was believed to be originally developed in 1946 by RCA engineers in Harrison, New Jersey under developmental number A-4522. Release date for public sale under the 12AX7 identifier was September 15, 1947. 12AX7 was originally intended as a low-cost amplifier for audio applications. Its wide use in guitar amplifiers (see Valve sound) has caused it to be one of the very few small-signal vacuum tubes to continue in production since it was introduced.

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The tube has a center tapped filament so it can be used as in 6.3V 300ma, or 12.6V 150ma heater applications. Other tubes with the same base include the 12AU7, 12AT7, and the fairly unknown 12AZ7. Of these the 12AX7 has the highest gain which is typically 100.

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Hundreds of different variations of the 12AX7 have been manufactured all over the world. Variations include the low-noise versions 12AX7A, 12AD7, 6681, 7025, and 7729; European versions B339, B759, CV492, CV4004, CV8156, CV8222, ECC83, ECC803, ECC803S, E2164, and M8137; and the lower-gain low-noise versions 5751 and 6851, intended for avionics equipment. Its popularity has made a complete cataloging of all manufactured variations impossible. In past decades, versions were known to be made in the USA, Canada, virtually every European country, Australia, Japan, India, Argentina, Chile, Brazil, China, USSR, and possibly in other places.

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Presently the 12AX7 is made in various versions by two factories in Russia, one in China, one in Slovakia, and one in Serbia, for a total annual production figure of 2 million units (estimated). The vast majority are used in new-production guitar amplifiers or for replacement purposes in guitar or audio equipment.

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Triode: A triode is a type of vacuum tube (or valve in British English) with three elements: the filament or cathode, the grid, and the plate or anode. The triode vacuum tube was the first electrical amplification device and still remains in use for amplification purposes, especially in audio-frequency appl...

Vacuum tube: In electronics, a vacuum tube (American English) or (thermionic) valve (British English) is a device generally used to amplify, or otherwise modify, a signal. Once used in most electronic devices, vacuum tubes are now used only in specialized applications. For most purposes, the vacuum tube has be...

RCA: : This article is about the electronics, audio, and video company. RCA is also the abbreviation for The Royal Regiment of Canadian Artillery. RCA is also used for RCA jack....