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The 12AU7 and its variants are a miniature nine-pin (B9A base) medium-gain dual triode vacuum tube. It belongs to a large family of dual triode vacuum tubes which share the same pinout (RETMA 9A). 12AU7 is also known in Europe under its Mullard–Philips tube designation ECC82.[1] There are many equivalent tubes with different names, some identical, some designed for ruggedness, long life, or other characteristics; examples are the US military 5814A and the European special-quality E82CC and E182CC.

Hitachi 12AU7.JPG
RFT "thin-plate" ECC82 variant (left), RCA 12AU7A variant (right), Hitachi 12AU7 (bottom)
ClassificationDual Triode
ServiceAudio amplifiers and TV receivers
Height2 58 in (67 mm)
Diameter78 in (22 mm)
Cathode typeCoated Unipotential
Filament voltage:200 V
Filament current20 mA (maximum)
Heater voltageSeries / Parallel
12.6 / 6.3 V
Heater currentSeries / Parallel
150 / 300 mA
Max dissipation Watts2.75 W per section
Max voltage300 V
Socket connections

The tube is popular in hi-fi vacuum tube audio as a low-noise line amplifier, driver (especially for tone stacks), and phase-inverter in vacuum tube push–pull amplifier circuits. It was widely used, in special-quality versions such as E82CC and 5814A, in pre-semiconductor digital computer circuitry. Use of special-quality versions outside of the purpose they were designed for may not be optimal; for example, a version for digital computers may be designed for long life without cathode poisoning when mostly switched to low-current mode in switching applications, but with little attention to parameters of interest only for linear applications such as linearity of transfer characteristic, matching between the two sections, microphony, etc.

This tube is essentially two 6C4s or two EC90s in the same envelope.

Double triodes of the 12AU7 family have a center-tapped filament for use in either 6.3V 300mA or 12.6V 150mA heater circuits.

As of 2012 the 12AU7 continued to be manufactured in Russia, Slovakia (JJ Electronic), and China.

See alsoEdit

  • 12AX7 - includes a comparison of similar twin-triode designs
  • 12AT7


  1. ^ " - 12AU7 / ECC82 Tube Types".

External linksEdit