{{short description|Miniature medium-gain dual-triode vacuum tube}} {{Infobox vacuum tube |image = 12AU7.jpg |caption = RFT "thin-plate" ECC82 variant (left), RCA 12AU7A variant (right) |classification = Dual Triode <!-- Mandatory --> |service = Audio amplifiers and TV receivers
|height_in = 2+5/8 <!-- inches --> |diameter_in = 7/8 <!-- inches --> |weight_lbs = <!-- pounds -->
<!-- Cathode --> |cathode_type = Coated Unipotential <!-- Mandatory --> |heater_voltage = Series / Parallel <br /> 12.6 / 6.3 V |heater_current = Series / Parallel <br /> 150 / 300 mA
<!-- Anode --> <!-- use either max_dissipation or max_current --> |max_dissipation = 2.75 W per section |max_voltage = 300 V |max_current = 20 mA (maximum)
<!-- Socket Connections --> |pinout = [[File:EIA-9A.png|183x78px]] |reference = http://www.thetubestore.com/lib/thetubestore/eh-12au7eh.pdf }} The '''12AU7''' and its variants are miniature nine-pin (B9A base) medium-gain dual-[[triode]] [[vacuum tube]]s. It belongs to a large family of dual-triode vacuum tubes which share the same pinout ([[RETMA tube designation|RETMA]] 9A). '''12AU7''' is also known in Europe under its [[Mullard–Philips tube designation]] '''ECC82'''.<ref>{{cite web|url=https://www.thetubestore.com/preamp-tubes/12au7-ecc82-tube-types|title=www.thetubestore.com - 12AU7 / ECC82 Tube Types|website=www.thetubestore.com}}</ref> 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 ECC802 and E82CC.
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 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 6C4/EC90s in the same envelope. However, this latter type is officially described in manufacturer's data as "a special quality R.F. power amplifier or oscillator for frequencies up to 150 MHz".<ref>Tung-sol Data sheet for 6C4/EC90 dated December 1968</ref> The 12AU7, on the other hand, is described as an "A.F. double triode".<ref>Tung-sol Data sheet for 12AU7/ECC82 dated August 1950</ref> Data sheets suggest an upper frequency limit of 30 kHz for the 12AU7/ECC82 and it is not described as a "special quality" device. <ref>Brimar application report VAD/513.4 for 12AU7/ECC82 dated January 1952 gives a gain of -1 to -2 dB at 30 kHz</ref> This contrasts with the 6AB4/EC92 and [[12AT7]]/ECC81 which are both R.F. devices operating up to [[VHF]]. Double triodes of the 12AU7 family have a center-tapped filament for use in either 6.3V 300mA or 12.6V 150mA heater circuits.
It was also widely used in television applications, mostly as line timebase oscillator, frame timebase oscillator, in some cases as gated automatic gain control, synchronisation separator, limiter, or, in some later colour sets, as relay tube, to turn off high voltage tube driver in case one of line failure or frame failure, to protect the picture tube, in the case of television where high voltage was generated separate from the line timebase.
{{As of|2012}} the 12AU7 continued to be manufactured in Russia, Slovakia (JJ Electronic), and China. [[File:12AU7 Tronix.jpg|150px|thumb|Tronix 12AU7|center]]
==See also== *[[12AX7]] - includes a comparison of similar twin-triode designs *[[12AT7]]
==References== {{reflist}}
== External links ==
* [http://www.nj7p.org/Tubes/PDFs/Frank/hb3/12AU7.PDF 12AU7 datasheet from the RCA RC-29 Receiving Tubes Manual] (NJ7P Tube Database) * [https://web.archive.org/web/20180412193231/http://tubedata.milbert.com/sheets11.html Several tube datasheets] * [http://www.tubemaze.info/tag/12au7/ Reviews of 12au7 tubes.] * [https://web.archive.org/web/20160304070845/http://www.jj-electronic.com/pdf/ECC%2082.pdf] (JJ Electronic ECC82 Datasheet)
[[Category:Vacuum tubes]] [[Category:Guitar amplification tubes]]