0
Shopping cart
0
Cart is Empty

The ’12AU7′ Tube

The 12AU7 is a miniature medium-mu twin triode. This tube finds use as a phase-inverter/splitter in push-pull amplifier circuits in ac/dc radio equipment and in many diversified applications such as multivibrators or oscillators in industrial control devices. The tube is quite pokey and sections can even be connected in parallel to create a power amp with enough current to drive a pair of headphones or even a guitar speaker. A centre tapped heater permits operation of the tube from a 6.3V or a 12.6V heater supply. The tube requires a noval nine-contact socket and may be mounted in any position.

DOUBLE TRIODE (separate cathodes)

b9a_miniature_tube_pinout — B9A base pinout

Heater Voltage	6.3-12	V
Heater Current	300-150	mA
Plate Voltage	250	V
Plate Current	10.5	mA
Plate Resistance	7700	Ω
Amplification Factor (μ)	20
Plate Dissipation (max)	2.75	W

12AU7 tube equivalents

Special thanks to Brent Jessee Recording & Supply, Inc.for kindly granting Effectrode permission to reproduce the following material below.

12AU7/12AU7A: The common U.S.A. version of this tube. The 12AU7 can only be used in parallel filament circuits. Like the 12AX7, this is not a hassle since virtually all hi-fi tube amps are of the parallel filament design. RCA, GE, and Sylvania actually made most of these tubes, regardless of brand on the label. The early RCA version has ribbed flat black plates with a top getter and a white label. This is an amazing tube, one of the best USA 12AU7 tubes ever made and we have a good stock of these. Still available, and still a bargain since everyone wants the “cleartops”: 1960s versions that have grey-plates and the getter on the side, making the top clear. These “cleartops” are currently the hottest selling 12AU7, and are still a great buy at current prices. Watch this tube….I predict in 5 years it will be as hard to find as the Telefunken smoothplate, and just as expensive! The 1970s new logo version (and the late 1940s-1950s version with the white label) of the RCA 12AU7 has greyplates and a top getter. This grey-plate RCA is about the best bargain you can get in a vintage RCA 12AU7. The GE versions pretty much always used grey-plates and a top getter for this tube. The numbers are etched into the glass with a pattern of dots below the number. Don’t miss trying the “organ stock” 12AU7 tubes that were sold to organ manufacturers. These sweet tubes were screened for audio use in organs, and have the organ brand on the label. Usually sold at bargain prices because of the re-branded label, the RCA cleartop and Raytheon blackplate versions are a great find! Tung Sol made an early “blackglass” version in the late 1940s, which hides the inside of the tube from view, and is very rare; later Tung Sol 12AU7 tubes look like early RCA grey-plates inside. All of these vintage tubes used a chalky label paint, and often the tube label is smeared or partially rubbed off. This does not indicate use or poor quality. Rather, it is an indication of a genuine vintage tube, and all of these are excellent quality.
ECC82: This is the European version of the 12AU7, and is identical to it. The brands in demand are Telefunken, Amperex, and Mullard. Telefunken tubes have a diamond shape molded into the bottom of the glass. Both ribbed plate and the more famous smooth-plate types are available, just like the 12AX7, but are being hunted down and soon may be an endangered species. Amperex and Mullard have tiny date codes etched in the glass near the bottom of the tube. The most popular Amperex are the Holland made Bugle Boy series, with the tiny cartoon tube blowing a bugle on the label. They later went to just a white label that said “Amperex”, and then after that used the orange label with the world logo. The earlier Mullard tubes had the word “Mullard” inside of a shield logo, later versions said “IEC Mullard”. Watch for the very rare long plate versions from the 1950s available in most European brands. These had narrow plates that were about 3mm longer than the 1960s and later versions. The earliest had square shape top getter elements, late long-plates have a halo top getter. Even rarer are the Mullard and Amperex made CV491 longplate square getter tubes, made only for the military. Most of these early Mullard tubes can be spotted not only by the date codes and longplates, but by the distinctive “wrinkle” glass, where the surface of the glass tube is not smooth but rather has tiny wrinkles or sometimes an eggshell texture. These are all tubes of unequalled quality, and are worth the high prices they are commanding these days. Even used ones will blow away any of the trashy tubes in production today. Vintage versions again used the chalky paint, and frequently the labels on any of these tubes are usually smeared.
CV491: A military specification version of the ECC82. These are usually found in Mullard or Brimar versions, but I have seen Siemens as well, and some made by Amperex. This tube was made into the 1990s so careful selection needs to be made. The best are the Mullard and Amperex longplates from the 1950s, which look identical to the longplate ECC82. Ei Yugoslavia made a nice smoothplate version into the late 1980s which sounds surprisingly good despite it’s late vintage “East Europe” stigma attached to it. Overall, these are a step up from the standard ECC82 tubes, since they have military specs.
5814: This is a military spec tube. Sometimes the vintage GE versions may be labelled JG-12AU7WA in white and have 5814 etched into the glass. These are all low microphonic thanks to their rigid mica supports. Older versions have a third mica spacer near the top. These “triple mica” versions are in great demand today. The broadcast versions of this tube are the GE 5-star, and the RCA Command series. These vintage tubes have just started to become a hot item, as N.O.S. stocks of the West Europe types become harder to find. These tubes can withstand many on-off cycles and mechanical shock without a problem.
6189/E82CC: This can be both a military spec tube and a premium industrial tube. Often, the military versions will be marked 12AU7WA in addition to having 6189 etched in the glass. The older vintage of these tubes are usually black-plate with the extra “triple mica” spacer at the top. GE made this in their 5-star line for broadcast. The RCA military 6189 is gold lettered 12AU7WA, has black-plates, and extra support rods. These are excellent step up tubes in the 12AU7 family, when you can find them! Look for super rare triple mica versions from Mazda, Siemens, and Mullard, some with silver plates. Among the best 12AU7 tubes ever made.
5963: This is a nice industrial type which is nearly identical to the standard 12AU7. RCA made a nice black-plate version of this tube, Sylvania has a gold pin version, and GE has it in their 5-star broadcast line. The plate voltage rating is a little lower than for a 12AU7, but for most applications, it will work fine. It has a rugged cathode and should be long lived, similar to the 5814. Watch this tube, as it is plentiful now and prices are low. As audiophiles discover it, the rush will be on!
6350: This tube was mainly manufactured for IBM and other computers in the late 1950s to mid 1960s. Sylvania and GE blackplates are considered the best of all with this tube. The only difference is the pins that correspond to the grid and plate of each triode are reversed from the 12AU7 connections, so you will either need to rewire your sockets to take this tube, or consult with the manufacturer of your unit to see if this tube can be used as a sub for the 12AU7. It has a mu or gain factor of 18 so is very close to the 12AU7. These were made to tight specs and carefully quality checked, since replacement in a computer of the day was difficult and costly, and the tubes were expected to operate 24-7. These make impressive upgrades to the standard 12AU7!
6680: Motorola and GE are the brands you find most often with this tube, but RCA made a nice cleartop version for a very short time. It is identical to the 12AU7, but has the added benefit of being able to withstand variations in filament voltage without affecting it’s output. This tube was designed originally for two-way mobile radio use. It makes a fine hi-fi 12AU7 tube as well. Never as plentiful as other types, this tube is rather scarce today.
7730: An excellent USA made industrial version of the 12AU7, produced mainly by CBS labs but I have seen it with other labels as well. This tube has thickly plated gold pins and was designed for critical aircraft and other exacting industrial applications. It has a long life heater, is extremely well balanced and a top choice for audio use. Very rare today.
ECC802: This is a premium version of the European ECC82, with matched triode sections. These are very rare in the USA, and often command very high prices.
E80CC/6085: This unusual European tube is basically an industrial type 6085. However, it’s specs are similar enough to a 12AU7 that audiophiles are grabbing them up while the prices are still reasonable. The heater life is rated at 10,000 hours, and some have gold pins. The larger box plate structure gives this tube low microphonics and silky smooth sonics. Some of the Philips Holland versions had the rare pinched waist, where the glass dips inward and actually molds around the top mica plate, giving the plates extra support and virtually eliminating microphonics. There is also a version made at the Amperex factory in Hicksville, NY, which is often priced lower but looks the same and sounds very similar to the Holland version. Since this tube has a much higher Gm and Mu factor than a 12AU7, the gain is going to be greater and this tube will give a more forward presentation. Awesome in phase splitter applications. If in doubt, check with your amp or preamp manufacturer to see if this tube will work OK in your application. This tube is also about twice as tall as a 12AU7, so installation space in your chassis is a consideration as well. These are out of production, rare, and getting very hard to find. The European types usually command the top prices, but U.S.A. types exist as the 6085 and should be a bit lower in cost, but they are also rare and climbing in price. Many U.S.A. tubes were actually made by the European factories, so watch for the 6085 U.S.A. brands!
B749: This is made by Genalex (Marconi-Osram Valve Co. of England) and is extremely rare in the U.S.A. The B749 is in the “Gold Lion” series of audiophile tubes, and has the gold lion and gold script on the glass. Inside it looks similar to a Mullard 12AU7, and has a red Genalex decal across the bottom. These are said to sound the best of all 12AU7 types, and this reputation, coupled with it’s overall scarcity, has driven the market price of this prize tube to extreme heights. Worth seeking out as these may be the first out-of-production classic European tube to go totally extinct over the next dozen years or so.

Cookie	Duration	Description
_GRECAPTCHA	5 months 27 days	This cookie is set by Google. In addition to certain standard Google cookies, reCAPTCHA sets a necessary cookie (_GRECAPTCHA) when executed for the purpose of providing its risk analysis.
cookielawinfo-checkbox-advertisement	1 year	Set by the GDPR Cookie Consent plugin, this cookie is used to record the user consent for the cookies in the "Advertisement" category .
cookielawinfo-checkbox-analytics	11 months	This cookie is set by GDPR Cookie Consent plugin. The cookie is used to store the user consent for the cookies in the category "Analytics".
cookielawinfo-checkbox-functional	11 months	The cookie is set by GDPR cookie consent to record the user consent for the cookies in the category "Functional".
cookielawinfo-checkbox-necessary	11 months	This cookie is set by GDPR Cookie Consent plugin. The cookies is used to store the user consent for the cookies in the category "Necessary".
cookielawinfo-checkbox-others	11 months	This cookie is set by GDPR Cookie Consent plugin. The cookie is used to store the user consent for the cookies in the category "Other.
cookielawinfo-checkbox-performance	11 months	This cookie is set by GDPR Cookie Consent plugin. The cookie is used to store the user consent for the cookies in the category "Performance".
JSESSIONID		Cookie used to allow the Worldpay payment gateway on the website to function.
machine		Cookie used to allow the Worldpay payment gateway on the website to function.
viewed_cookie_policy	11 months	The cookie is set by the GDPR Cookie Consent plugin and is used to store whether or not user has consented to the use of cookies. It does not store any personal data.
wordpress_logged_in_		Users are those people who have registered an account with the WordPress site. On login, WordPress uses the wordpress_[hash] cookie to store your authentication details. Its use is limited to the Administration Screen area, /wp-admin/ After login, WordPress sets the wordpress_logged_in_[hash] cookie, which indicates when you’re logged in, and who you are, for most interface use. WordPress also sets a few wp-settings-{time}-[UID] cookies. The number on the end is your individual user ID from the users database table. This is used to customize your view of admin interface, and possibly also the main site interface.
wordpress_sec_	1 year	Provide protection against hackers, store account details.
wordpress_test_cookie		Test to see if cookies are enabled.
wp-settings-	1 year	WordPress also sets a few wp-settings-{time}-[UID] cookies. The number on the end is your individual user ID from the users database table. This is used to customize your view of admin interface, and possibly also the main site interface.

Cookie	Duration	Description
_ga	2 years	The _ga cookie, installed by Google Analytics, calculates visitor, session and campaign data and also keeps track of site usage for the site's analytics report. The cookie stores information anonymously and assigns a randomly generated number to recognize unique visitors.
_gid	1 day	Installed by Google Analytics, _gid cookie stores information on how visitors use a website, while also creating an analytics report of the website's performance. Some of the data that are collected include the number of visitors, their source, and the pages they visit anonymously.

Cookie	Duration	Description
mailchimp_landing_site	1 month	This cookie is used to keep track of newsletter sign ups and client emails at checkout, Mailchimp utilises cookies to store information captured from user input for remarketing purposes.
mailchimp_user_email	1 month	This cookie is used to keep track of newsletter sign ups and client emails at checkout, Mailchimp utilises cookies to store information captured from user input for remarketing purposes.
mailchimp_user_previous_email	1 month	This cookie is used to keep track of newsletter sign ups and client emails at checkout, Mailchimp utilises cookies to store information captured from user input for remarketing purposes.
mailchimp.cart.current_email		This cookie is used to keep track of newsletter sign ups and client emails at checkout, Mailchimp utilises cookies to store information captured from user input for remarketing purposes.
mailchimp.cart.previous_email		This cookie is used to keep track of newsletter sign ups and client emails at checkout, Mailchimp utilises cookies to store information captured from user input for remarketing purposes.

Shopping cart

The ’12AU7′ Tube