Guide to NOS and Vintage Audio Tubes

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Guide to NOS and Vintage Audio Tubes

Post by Structo » Wed Apr 25, 2012 12:22 pm

Hey guys,

Here is some information on noval preamp tubes.

From brands, long plate, short plate, grey plate, black plate, etc. ... 0017053944

Credit to thetubeking on eBay

Also at AES they have a comparison for current production preamp tubes. ... made_tubes

The Tubeking's 'Tube Tasters Guide'

Hi folks. If you're anything like me, then you're passionate about vintage and NOS audio and guitar tubes. So I am writing this guide to give my customers information about these fantastic tubes... how, when and where they were made, how to decipher tube codes, and most importantly, how they sound. I will also detail long vs. short plate and gray vs. black plate. I am mainly going to cover 12AX7/ECC83 and 5751 type pre-amp tubes and EL84/6BQ5 power tubes: since these are some of the most popular and in demand tubes for guitarists and audiophiles. I will also get into tube dampers, and how these dampers can greatly improve tube sound and performance in guitar and audio applications. I will also briefly discuss the real meaning of a 'NOS' tube, tube faking, and overcharging for tubes by some dealers.

European ECC83/12AX7 :

ECC83 is the European designation for the 12AX7 tube -- (it is the same exact tube). These tubes include those produced by Mullard, Amperex, Siemens, Telefunken, Tungsram, RFT, Ei, Mazda, Lorenz, Philips and others. European ECC83s are generally sought after for their warm sound (with exceptions -- Telefunken, for example). These tubes emphasize even order harmonics, so you get a warmer clean sound, and a very harmonic overdrive sound in a guitar amp which is very pleasing to the ears. I will detail the sound of each European tube type below.

USA 12AX7/ECC83:

These tubes include those produced by RCA, GE, Sylvania, Tung-Sol, Raytheon, Ken-Rad and a few others. USA 12AX7s tend to emphasize the fundamental tone, rather than the even order harmonics (with exceptions - please see 'Black Plate tubes' below). This means that they generally have a cleaner sound and a more 'American' overdrive. These types of tubes are very popular among Fender users, who are looking for a classic 1950s-1960s rock and blues sound. The exception to this rule are the black plate tubes produced by RCA, Sylvania, Raytheon, and Ken-Rad. These tubes have a very warm 'European' clean sound and a fantastic 'harmonic' overdrive sound. I will detail the sound of each tube below.

Also you might want to read this note on tube 'paint.' Logos and labels on a tube mean nothing -- except possibly paying too much money for a tube and causing confusion. All the major European and USA tube manufacturers produced tubes under many different logos. Some of these tubes were 'OEM, - Original Equipment Manufactured' for other companies. This means that, for example, producers like RCA or Mullard manufactured tubes for other companies, and would put a different company logo on the tube. A Mullard tube that says 'The Fisher,' 'Bogen,' or 'Knight,' is still a Mullard tube. It can also get confusing because some companies 'cross-labeled' their tubes. For example, you can find British Mullard ECC83s that are labeled Holland Amperex, and vis-versa. Sometimes a Mullard that says 'Gt. Britain' on the tube can actually be an Ei, RFT or Amperex. Same goes for other American or European tubes. It gets even more confusing when you find European ECC83s with American logos such as RCA or GE. That's why it is important to understand tube construction, tube codes, and tube history, or at least purchase your tubes from someone who does. The real determinants for a tube are construction, when and where it was made, and etched codes. In other words, an RCA or Telefunken that is labeled Zenith or Fisher is the same exact tube as a 'real' RCA or Telefunken, provided they were made in the same factory with the same codes. We carefully screen, inspect and test all the tubes we sell to make sure you are getting exactly what you pay for.


The 12AX7/ECC83 comes in two main types (with some exceptions): 17mm Long Plates and 14mm Short Plates. It is important to know the differences between these tubes, since sound and performance can differ greatly between the two types. Long plate 12AX7s were the first tubes of this type ever produced. These include tubes by such makers as RCA, Mullard, Amperex, GE, Ken-Rad and so on. As a rule, Long Plates usually fetch higher prices than short plates. One of the first Long Plate 12ax7s is the Blackplate Ken-Rad, which is a very fine tube. Short plate 12ax7 tubes were first produced in the early 1960's by the likes of RCA, GE and so on, and then picked up by the European producers such as Philips, Mullard and Amperex. Companies developed short plates in an attempt to provide a longer lasting tube with resistance to noise and microphonics. The main sonic differences between Long Plates and Short Plates can be summed up in three words: '3-D,' 'Lively,' and 'Open'. By and large, Long Plates have a bigger sound in guitar and audio amps than short plates (with exceptions.) However, Long Plates can sometimes be vulnerable to noise and microphonics. Short plates are more stable in guitar applications, although Long Plates usually do okay, especially when equipped with tube dampers. Sometimes the differences in sound between the two types can be subtle. It really depends on your taste and what you are going for. Personally, I usually favor Long Plates in V1 of my guitar amp and short plates in V2 (overdrive slot). However, there are exceptions to every rule. For example, to my ears, Tungsram and Mullard I61 ECC83s have a big sound similar to Long Plates. My advice is to buy a bunch of Long and Short plates and try them out in different applications to see what you like. Each type has its place in home audio and guitar amps.


This distinction mainly applies to classic American made tubes. The first 12AX7s produced were all black plates, and are considered very desirable tubes due to their fantastic and sweet sound. Manufacturers of black plate 12AX7s included: RCA, Sylvania, Tung-Sol, Raytheon and Ken-Rad. The Ken-Rad was one of the first 12AX7s, (black plate or otherwise), dating around 1949. USA black plate 12AX7s sound much different than USA gray plates, and can be compared to some premium European ECC83s. In general, black plates have a warmer, more complex, harmonic and fuller sound than US gray plates. They emphasize even order harmonics rather than the fundamental tone. They have a really nice and full clean sound in a guitar amp, and a complex, aggressive and saturated overdrive. Audiophiles also seem to love US black plate 12AX7s (and 5751s). There are differences in sound between the different brands of black plates: some have more high end, some are warmer, some are more aggressive, some are more cutting. However, you can't go wrong with any of the brands... all made fine tubes. Genuine RCA black plate 12AX7s can be identified by their dull color and a horseshoe or square getter. Sylvania black plates are much shinier and usually have a square getter. Raytheon black plates are also very shiny and will have a square or halo getter. Ken-Rad and Tung-Sol made some very fine and rare black plates as well. My advice would be to buy a bunch of different branded black plate 12AX7s to find your favorite 'taste.' They can be a nice change of pace from US Gray plate 12AX7s.


Mullard ECC83:

One of the most sought after tube by guitarists and audiophiles, British Mullards (produced at the Blackburn Factory) have a warm 3-D syrupy midrange sound, unlike any other tube in existence. They have a fantastic 'tweedy' clean and overdrive sound in a guitar amp. Many audiophiles prefer these tubes to add 'life' and 'warmth' to a sterile or bright sound system. The famous Mullard mid-range is great at reproducing vocals, especially female. And Mullards can really improve the sound of a guitar amp, since its classic mid-range suits this instrument perfectly. Many of the classic rock records we are familiar with have the Mullard sound, especially all the old recordings done on Marshall guitar amps. So you will immediately recognize this sound when you hear it. Many 'blah' tube amps can greatly improve when stocked with some nice Mullards.

However, you should know which Mullard ECC83 type you are getting, because the sound can differ significantly between each type.

MC1 Long Plate Square Getter: The most sought after, early production and expensive Mullard ECC83 from the mid-1950s. This one has 17mm long gray ladder plates and a dual supported square getter. This is the ultimate 'Mullard' sound.... big, open and warm with a tweedy harmonic overdrive. The etched MC1 code on the bottom of the glass denotes this type, along with the 'B' Blackburn Code + a Number and a Letter.

F91 Long Plate Dual Halo Getter: Similar in sonic characteristics to the MC1 Mullard above. This version comes from the late 50's (roughly 1957-1958) and will sometimes come with a square getter. It sounds very similar or the same to the MC1 Mullard, but is usually a bit less expensive. You can tell this type by the etched F91 code on the bottom of the glass, along with the 'B' Blackburn Code + a Number and a Letter.

F92 Long Plate Single Halo Getter: Similar in sonic characteristics to the F91 Mullard above. This version comes from the late 50's (1959) and will have a single supported halo. It sounds very similar or the same to the MC1 Mullard, but is usually somewhat less expensive. You can tell this type by the etched F92 code on the bottom of the glass, along with the 'B' Blackburn Code + a Number and a Letter.

I61 Short Plate Halo Getter: This is the first short plate Mullard ever produced and was made around 1959-1964. A great tube with that classic 'Mullard' sound, this tube has the benefit of resistance to microphonics due to the plate structure. At the same time, the open 3-D midrange sounds similar to the long plate Mullards, with a little more balls. One of my favorite guitar tubes. You can tell this type by the etched I6I code on the bottom of the glass, along with the 'B' Blackburn Code + two Numbers and one Letter.

I63 Short Plate Halo Getter: This is the second short plate Mullard ever produced* and was made from 1965 onwards. This tube is a bit more compressed than some of the Mullards listed above, so it is favored by many rock guitarists for its distortion characteristics. Many people will use an I61 or F91/F92 tube in the V1 (first slot) of their guitar amp for overall sound, and then put an I63 type in their overdrive slot (usually V2 or V3). This can be an ideal combination, depending on your amp and what you are going for. You can tell this type by the etched I63 code on the bottom of the glass, along with the 'B' Blackburn Code + two Numbers and one Letter. *(There was actually a very short production run "Yellow Label" Mullard ECC83 produced right before this tube.)

CV4004 M187 ECC83 Box plate: The CV4004 box plate Mullard is a military production tube that can be identified by its unique plate structure. This is a well built, highly desirable and favored tube by audiophiles. Many swear by this tube for their home tube stereo systems, and prefer them to regular Mullards. Some guitarists use them in their amps, but most seem to prefer regular Mullards. Produced at the Mullard Mitchum Factory these tubes can usually be identified by the 'R' code etched in the bottom of the glass + a Number and a Letter.

Mullard 10M Master Series ECC83: These were specially made, later production Mullard short plates that are rated for 10,000+ hours in a tube amp. They were also specially selected for low noise and balanced triodes. They can be identified by the Gold Mullard '10M' Logo on the tube and they have gold or regular pins. The Gold Pin versions are superior and worth more. These tubes are highly sought after by audiophiles. They have a wide-band sound similar to a Telefunken, but with a touch of that Mullard warmth. They are quite rare, and can fetch insane prices, especially if they are NOS. I finally got a chance to hear this tube in my guitar amp and I am impressed... fabulous balanced clean sound with a touch of brightness.... incredibly SWEET. Overdrive was pretty cool as well. I can see why audio guys go crazy for these tubes.

There are other Mullard ECC83s that were produced later, but the tubes listed above are the ones you should look for. Beware of fake Mullards being sold on ebay. These will often have 'perfect' baked-on enamel labels that will not wipe off. These labels usually look too thick and 'painted-on' in pictures. Real silk-screened Mullard logos look much more delicate in pictures. Sometimes Matshushita tubes will be sold as Mullards with Shield logos. These are Japanese tubes that were made on Mullard tooling so they look similar to I63 Type Mullards. Not a bad tube, but be aware that some vendors will relabel these to pass them off as the real thing. Sometimes you will see "OEM" Mullards that originally had no labels branded with a fake Mullard label from another era. This can also happen with British 'Brimars' which can have fake Mullard labels. There are also people on ebay selling 'Mullards' with obviously new, fake and cloned 'Mullard' boxes that look nothing like the real thing.... unbelievable. Always purchase your tubes from reputable dealers. We carefully screen each and every tube we sell to make sure they are authentic.

Amperex ECC83:

This type includes the famous 'Bugle Boy' ECC83 produced at the Herleen, Holland factory but can mean any Herleen, Holland ECC83, which is the exact same tube regardless of paint or logo. These tubes are very sought after by guitarists and audiophiles for their nice combination of 'warm' and 'clean' tone. They have a nice warmish mid-range with balanced clear highs and lows. To me, these Dutch tubes have an 'Orange' sound. Clear, bright and warm at the same time. They also have a very nice harmonic overdrive in a guitar amp. There are a few types of these tubes to look out for. Please note: all Herleen Amperexes should have a 'Delta' symbol code etched on the bottom of the glass. (Looks like an 'unequal' triangle.)

MC6 Foil D Getter Long Plate: This is the earliest Amperex/Bugle Boy, produced at the Herleen, Holland factory in the mid-1950s. This tube can be identified by its 17mm long gray plates and unique 'D' getter with a piece of foil attached. This is the most desirable and expensive Amperex ECC83. It has the classic Holland Amperex sound as detailed above, with the added 3-D open effect of the long plates. I really like the overdrive qualities of Amperex.... nice and richly harmonic, but focused at the same time. A great tube for audio or guitar. You can find this tube by the etched MC6 code, along with the Herleen Delta symbol + one number and a letter on the bottom of the glass

I65 Short Plate Halo Getter: This is the main other type of Amperex tube produced at the Herleen Factory in the 1960's. It sounds VERY similar to the MC6 long plate, albeit a tad less open. This type of tube usually has a halo getter. Earlier and more sought after versions have a very large halo getter. Later versions have a smaller halo getter while even latter versions have a 'disc' or 'dimpled' getter. Also, later versions of this tube were produced under the 'Orange Globe' logo. Many times you can find Herleen, Holland Amperex with a 'Hammond' logo. These are very nice low noise tubes that were highly screened for use in organs. They are the same as any Bugle Boy or Amperex ECC83, except screened for higher quality. Hammond Amperexes are one of my favorite tubes... I buy them whenever I can. I have found certain Hammond Amperexes to be exceptionally sweet, as good or better than any 'Bugle Boy' labeled tube. In general you can identify most of these tubes by the I65 code etched in the bottom of the glass along with the Herleen Delta symbol + a few numbers and letters, depending on the year.

You can also look out for Amperexes with other labels: Miniwatt, Philips and others. These are the same exact tube as any Amperex Bugle Boy ECC83. Also look out for the rare 'Medical Grade' Amperexes. These were specially screened for use in medical equipment and have medical markings on the tube usually stating 'for medical use'.

Tungsram Hungary ECC83 :

A fantastic underrated tube, the Tungsram Hungary is one of the best guitar and audio tubes in existence. It is also a VERY well built and uniquely constructed tube. This tube has a great European sound in a guitar amp.... very well, perfectly balanced 'colorful' harmonic clean tone and beautiful overdrive when pushed. The Tungsram Hungary also has one of the best extended top ends out of any ECC83, and it is never harsh. Sounds similar to an Amperex D-Getter, but I like the Tungsram better. Fantastically balanced for audio use as well. Tungsrams are also very well built. They have thick dual getter supports that run all the way down to the first mica. Very few ECC83s have this construction. The only other one I am aware that has similar construction is the Silver plate Mazda. You can also identify Tungsrams by the unique numbered 'Silver Foil Square Tag' that is usually attached to the getter supports. The Foil Square is usually located higher up on the tube for later production versions. (I.E. 1960s vs 1970s). One of my all-time favorite guitar and audio tubes. Keep an eye out for the rare 'RCA' branded Tungsrams. They sound fantastic as well. (I have one but I'm not selling it!). Every guitar player or audiophile should own at least one Tungsram. (Preferably three or four!) NOS Tungsrams need to be 'burned in' for at least 48 hrs for optimal sound. These are getting harder to find and prices are going up.

RFT East Germany ECC83

This is a very interesting, somewhat unknown tube. It is constructed with the thickest glass out of any ECC83. It is a very stout tube with great resistance to microphonics. The ultra-short plate structure and windmill mica is unique as well. Among those in the know, RFT is famous as a great hard rock 'crunch' tube in a guitar amp. It is favored by many Marshall and Mesa players for this reason. It is a somewhat 'warm' tube with a rolled-off high end, so it can help with overly bright guitar amps. If you are interested in trying the RFT ECC83, it is best used in the 'overdrive' pre-amp slot in your guitar amp. You probably would not want to use it in the main pre-amp slot (V1), since it is not an overly detailed tube. A really good combination that I use in some of my amps is a Mullard in V1 and an RFT in V2 (overdrive). This will give you a great general tone and a fantastic warm distortion. Another benefit to RFTs is that they last forever and you can run them really hard without worrying about noise and microphonics, although they take a while to break in.

Telefunken ECC83

A well known tube among audiophiles and guitarists, some people regard the Telefunken ECC83 as the ultimate pre-amp tube. It is used more commonly by audiophiles. The Telefunken is considered a wide-band 'neutral' or 'clear' tube. It does not really impart any color to the sound. Therefore, if you have an overly warm stereo or guitar amp, you may want to consider this tube. There are two main types of Telefunkens: smooth plates and ribbed plates. The smooth plates are usually more desirable and expensive for audiophiles, probably because people consider this type to be more 'neutral'. Telefunkens are not used in guitar amps as much as other ECC83 types. I have found that the smooth plate Telefunken lacks personality in a guitar amp and does not really overdrive well. The ribbed plates are a little better in this regard. However, there is a good place to put a Telefunken smooth plate in a guitar amp... in the phase-inverter slot (usually the last slot closest to the power amp tubes.) I have found that this can add some 'clarity' and '3-D' effect to your overall sound. Genuine Telefunkens always have an etched diamond shape on the bottom of the tube between the pins, so you must always look out for this. Telefunkens are also commonly faked, even with the diamond bottom. Usually these fake Telefunkens will have perfect labeling that is 'baked-on' and will not rub off with a cloth. This is a dead-giveaway that you are dealing with a fake. The labels on real Telefunkens are always fragile and will easily rub off. Look out for Telefunkens with other labels: Fisher, Gap-R Computor and others. These are genuine Telefunkens and can usually be had at special prices. There are also highly regarded 'Lab Quality' Medial Telefunkens that were produced for Leeds & Northrup Grummond. These will usually have red tips, say 'Selected' somewhere on the tube, and are sought after by audiophiles who will pay insane prices for these tubes.

Ei Yugo

These fine tubes were produced at the Nis Factory in Yugoslavia on Telefunken tooling. The tube itself has smooth long plates and resembles a Telefunken, but that is where the similarity ends. Ei Yugos are excellent to use in guitar amps and audio. In audio, they have a clear and aggressive sound, somewhat like a Telefunken 'on-steroids' with more personality. Eis are also a great tube to use in guitar amps, provided you can find one that is not microphonic. They have a nice detailed, balanced and very punchy clean sound and a great aggressive overdrive with extended high end. Good Eis are one of my favorite guitar tubes and Dr. Z seems to agree (from what I have read). Eis are no longer being produced and are getting harder to find. Just do an ebay search... there are always many more Mullards available than Eis. Eis come in two styles: gray and silver plates. The gray plates were produced earlier and are more popular. However, many people also like the silver plates. You want to try and find what are called 'Pre-War' Eis. These were produced at the Nis factory prior to the conflict in Yugoslavia in the 1990's and are considered superior. Ei's from the 1970's can fetch high prices. These are usually rebranded tubes that don't always say Ei on the logo. However, Eis from the 80's-early 90's are fine tubes as well. The only problem with Eis is that some tend to be microphonic. Therefore, you would want to make sure to buy from a reputable dealer who screens tubes. That being said, I have used many Eis in the past and have found only one to be microphonic. They usually will do okay. I believe that the Ei 'microphonic problem' is a bit over hyped. These tubes are fantastic in any guitar amp, but are particularly good in Vox style amps. You can use the Ei ECC83 in any slot of your guitar amp, especially the main slot and the overdrive slot. An interesting fact about Eis is that they usually have seams on top and will 'flash' on start-up like a good Mullard or Amperex. I will be trying to procure a good stock of NOS Ei Gray and Silver plates in the near future for my customers.

USA 12AX7 AND 5751

RCA 12AX7:

RCA ('Radio Corporation of America') is the most well known company that produced tubes in the USA, and their 12AX7s are among the most popular NOS and vintage tubes looked for by musicians and audiophiles. RCA also produced some of the earliest 12AX7s and made many innovations in tube manufacturing that were copied by other companies. Many RCA tubes came standard in vintage Fender amps and are considered a big part of that 'Fender' sound. Some RCA tubes are popular with audiophiles, especially the 5751 tubes like the RCA Command Series and some RCA Blackplate 12AX7s. You can break down RCA 12AX7 tubes into three common types:

Gray plate 17mm 12AX7:

These tubes were produced from the late 50's to early 60's. They have 17mm ribbed ladder plates and a horseshoe, 'D,' or halo getter. Earlier versions will have the horeshoe/D getter, and are worth more. These tubes have that classic 'RCA' sound in a guitar amp: a bell-like clean tone and a 'Phat' somewhat gritty overdrive. They are popular with Fender users and other people interested in an early rock and blues sound. A very sweet sounding tube. Keep an eye out for the rare, low noise version of this tube.... the 7025 Gray Long Plate. I don't come across these too often. (They are much less common than the 14mm RCA 7025 Short Plate.) Also look for Baldwin or Lowrey branded RCA long plate 12AX7s. These were specially selected low noise tubes made for organs and represent high quality RCA tubes. They were once a bargain, but prices have been going up recently as more people discover these tubes.

Black plate 17mm 12AX7:

This is the first RCA 12AX7s ever produced and it is one of the most sought after 12AX7 black plates. They were manufactured starting in the early 1950's and can be identified by their 17mm dull ribbed Black plates and a horseshoe or square getter. Earlier versions have the square getter. These are highly regarded tubes by audiophiles and guitarists, and can command high prices, especially if they are NOS. Like all black plates, these have a more complex, harmonic sound similar to some European tubes. The clean tone is very colorful and balanced and the overdrive is harmonic and very saturated in a guitar amp, with a touch of high-end roll off. Audiophiles who are looking for a warm yet balanced tube will probably like the RCA 12AX7 as well. One of my favorite black plate 12AX7s.

Gray plate 14mm 12AX7:

The most common RCA 12AX7 type, the Gray 14mm short plate was produced from the mid-60's onward and came standard in many Fender and other American amps of the era. They will have 14mm gray ribbed plates and a halo getter. These tubes have a similar sound to the RCA Grayplate 12AX7... bell-like clean tone and gritty overdrive. They are a bit 'less open' than their long plate counterparts, but still fine tubes. Look out for the 7025 low noise version of this tube... many people consider it to be superior, with slightly different sonics. RCA short plates can be had at a reasonable price, although can be somewhat costly if 'perfect' NOS.

Black Plate 14mm 12AX7

There is also a rare Sylvania 12AX7 with Short Black Plates and a Rectangular Getter. It looks similar to the Raytheon Black Plate 5751, except without Triple Micas and Gold Pins. These are very high-quality nice sounding tubes. The clean sound is very colorful with a warm tint, and the overdrive is rich and ballsy. Sylvania Black Plates usually have a little more treble on tap than, say, an RCA Black Plate. If you have a dull or overly warm sounding tube amp, try out this tube... it will give you more treble extension while still retaining the character of the amp. These sound similar to the more common Sylvania 12AX7 with Long Black Plates, but they are more durable in a guitar amp with less chance of microphonics, and have much better overdrive. 14mm Black Plate 12AX7s are quite rare and can fetch high prices.

80‘s/90‘s Beijing Chinese Military Square Getter Triple-Mica 12AX7

Another tube I really like is the Chinese Military Beijing 12AX7. This tube was manufactured in the 1980‘s-1990‘s in the Beijing Factory in China and features a Solid Foil Square Getter, Triple-Micas, and Military Markings. The sonic hallmarks of this 12AX7 are extreme clarity and a very low-noise floor. A ruggedly-built tube, the Beijing is perfect for high-gain applications, since it is quiet and very resistant to microphonics. In fact, the Beijing contributed a great deal to the 1980‘s “Marshall/Mesa Sound.” A lot of hard-rock guys go crazy for these particular tubes. They have great gain and a viscous rich distortion sound. These tubes have a surprisingly nice clean tone as well, which is good for blues, funk and rhythm guitar. The clean sound can be described as “clear and round with balanced bass, mids and highs." They have a very nice treble that is never harsh. I have used them in many amps, including Peavey Classic 30‘s and 50‘s with great results. In fact, I was shocked at how dead silent my modified Classic 30 became when I popped one of these Beijing 12AX7s into it’s V1 pre-amp slot. You will be surprised at how quiet your amp becomes with it’s ‘jet black’ background in both clean and high-gain use. If you want (V1) a slightly warmer tone with huge overdrive, try a Mullard I61 or I62 in the first slot of your amp and a Beijing in the distortion slot. These 12AX7s also work quite well in the phase-inverter slot in a tube amp, and sound great in home audiophile applications because of their clarity.

It is important to note that these older production tubes sound nothing like the newer mass-produced Chinese Shuguang 12AX7s, which can have a very harsh and unmusical tone. There is constant debate on the Internet about which new Chinese version is the best, and how to identify a tube from the correct production run. I have found that the older NOS Chinese Beijings are far superior in sonic quality to any new production Chinese tubes. You must make sure to look for the ones that have a Dual-Supported Square Foil Getter. Sometimes these tubes have white Military ‘Star’ markings. Others have ECC83/12AX7 written vertically in thick red paint on the side of the tube. Still others were re-branded by companies such as Groove Tubes. Regardless of the paint, all the Square Getter Beijing 12AX7s are the same tubes and sound great. Remember that the Beijing tubes were produced for the Chinese military and, as such, are very well built and reliable. They are no longer being produced and are still considered a bargain for such a quality tube. Most of these tubes list for around $16.95-$19.95 on the Internet when you can find them. I buy them whenever I can and recommend them to all my customers. The Beijing is a great quality economy pre-amp tube, and you will be surprised at how good these can sound in the right applications.

Credit to thetubeking on eBay.
Last edited by Structo on Thu Oct 18, 2012 9:46 pm, edited 5 times in total.

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Post by Structo » Mon Sep 17, 2012 9:02 pm

Here is more information on different preamp tubes.

ECC83 - European designation for 12AX7

12AX7 - The 12AX7 is a high-mu twin triode which operates in typical service as a class A amplifier, in the preamp stages of high fidelity, musical instrument, and public address amps, as well as professional line and microphone preamps, and many other audio and communications devices. The demand for the vintage USA and European versions of this tube are beginning to outstrip the supply, and, as a buyer, you need to carefully consider what is available, the device you will use it in, and what your budget allows. The highly regarded vintage brands of Telefunken, Mullard, Amperex, and RCA come at an appropriate premium price over other brands. While this higher price is justified (these tubes sound wonderful and are very long lived) other vintage brands are often just as good. Brands like GE, Sylvania, Tung-Sol, Motorola, Raytheon, and Zenith are often overlooked, but usually perform just as well as the more famous vintage brands, which makes them a terrific value, especially as the stocks of New Old Stock (NOS) tubes vanishes. Indeed, some of these were made by RCA for these other labels, and others like the Tung-Sol and Sylvania have their own followers who prefer these brands over the higher priced premium labels. There is intense hype out there about the 12AX7, and even some absolute fantasies. Some of the European labels have strong snob appeal, which can cloud accurate judgment of these very good tubes, and many self-proclaimed tube experts have either praised or shot down some vintage brands which deserve neither. If you are new to tubes in general, or are replacing a set of Russian or Chinese current production 12AX7 tubes with vintage NOS, you would do well to try several different brands and hear for yourself the sonic nuances. Then you would be well advised to lay in a stock of the brand of your choice "for a rainy day".
the original version of this tube. This can only be used in parallel filament circuits. This is not a big deal as virtually all audio equipment is of a parallel filament design. These often have large rectangular plates with several horizontal ribs. The older versions have blackplates, which are often preferred by audiophiles.

ECC803(S), E83CC, E803CC, 6L13 - This is a premium European version of the ECC83. The "S" indicates Special, and these tubes were screened for low noise and matching internal triode elements. These are rare in the USA. Telefunken and Siemens are the brands most often spotted, although several of the Mullard factories made these for various labels. Most of the Telefunken and Siemens tubes had gold plated pins. BEWARE: I have seen smoothplate Telefunken ECC83 tubes on auction sites with aftermarket gold plated pins, being passed off as NOS ECC803S tubes!! The ECC803S is a frame grid tube, and it's inside construction is different from a smoothplate. The ECC83 smoothplate or ribbed plate Telefunken tubes NEVER had gold pins! Be careful, and get a solid return policy like ours whenever you buy costly tubes like these. Sometimes the E83CC also carried the 12AX7WA military type label, even though it is a European made tube. The build quality and performance of these tubes are similar to the Mullard 10M type listed above, although the sonics will differ between German, Dutch, and British tubes. The 6L13 is rarely seen, and then usually only in a Mullard made longplate, but these are well worth the high price they command. They were made for other brands as well but all have the 6L13 on the label.

12AX7A - This version can be used in series or parallel filament circuits. These usually date to the 1960s and have greyplates. Vintage versions of these are about the most sought after tubes of any type today. Often RCA and GE made these for electronic organ manufacturers, and have the organ brand name on the label. These are usually specially selected tubes, and are a great buy---when available! Sometimes, 12AX7A tubes made for the US Military are labeled 12AX7WA, and I have seen WB and WC versions. The W is the military type code, A,B, and C are progressively later productions. These are nice military spec tubes. DO NOT confuse these with current production Russian or Chinese crap with the suffix WX, WB, or WC! These are not military tubes and are not NOS tubes at all!

12AX7WA - Premium military and industrial versions of the ECC83/12AX7.

12DF7 - This rather rare tube was only produced in the USA. It is an excellent replacement for any 12AX7, ECC83, or 7025 and is an improvement on these tubes. It was engineered to be very low noise and very low microphonics, designed for industrial and professional applications and equipment where high performance from the tube is critical. Seen with Westinghouse labels or OEM industrial equipment labels or part numbers, sometimes pasted right over the Westinghouse label. A great tube if you can find them, perfect for audio use!

CV4004 - The Mullard CV4004 is rugged version of the 12AX7. Made for the English Military, the CV4004 is one of the best 12AX7 variants you can use for audio.

5751 - This version was usually the one made for the US military. These have a lower gain than the 12AX7, but are otherwise totally compatible. Great hi-fi tubes, as the lower gain reduces noise and microphonics. These are all ruggedized and most can withstand a drop on the floor. The internal triode elements are matched as well. The early versions are more sought after as they usually have extra support rods and an extra mica spacer on top of the plate structure ("Triple Mica"), as well as blackplates, all said to contribute to low microphonics. Don't overlook the greyplate versions, they are also excellent tubes, and many of these have the triple mica as well. The GE non-military version is usually the "five star" series, intended for broadcast use. The RCA broadcast type is the "Command" series. Both the RCA and GE broadcast types are scarce, as are any of the triple mica types.

7025 -This is the low noise, "industrial" version of the 12AX7. This has a spiral wound filament which reduces hum and noise. These are usually the best choice for demanding hi-fi applications, although the premium brands and blackplate types also have very low noise.

B759 - This is an ultra-low noise version of the 12AX7, with matched triode elements. To my knowledge, only Genalex (Marconi-Osram Valve Co.) made these in England for their "Gold Lion" series. Extremely rare in the USA.

6681-This is listed in some tube manuals as a "special 12AX7", otherwise the electrical specs are the same as the standard version. Being an industrial type it most likely has a ruggedized filament, and is built to withstand many on-off cycles. I believe only RCA made these, regardless of brand on the label. UPDATE: One astute customer has informed me that GE offered 6681 tubes with the typical top seams, date codes, and "Gt. Britain" marking that indicates English Mullard manufacture. Indeed, some GE 12AX7 and 7025 tubes from the 1970s were also Mullard made, so they must have made some 6681s for GE as well. Overall, the 6681 is an excellent step up in quality from the standard 12AX7, and is a bargain at current prices.

7729 - This is another industrial tube like the 12DF7 above, manufactured for critical industrial, avaition, or medical uses. This tube is nearly always seen as CBS manufacture, and has thickly plated gold pins. Sometimes the equipment manufacturer put their part numbers or ID label right over the CBS label. Rarely found today but sometimes boxes of them turn up in the back hangars of avaition equipment suppliers and small aircraft maintainence shops. Superior in every way for audio use!

E283CC - Shock and vibration resistant, long life tube.

ECC808 - High quality noval preamp tube similar to 12ax7 specs but different pinout.

M8137 - The M8137 is a special quality version of the definitive audio double triode the ECC83. This high impedance amplifier triode was designed specifically for audio use and has a high amplification factor of 100.


A tough question if there ever was one! The best advice is to get a few types and hear for yourself the good sounds you have been missing. All of these vintage tubes are excellent, much better than the Russian or Chinese yuck that is being made today. When replacing any stock Russian, Chinese, or East Europe tube with any of these vintage NOS types, you will notice immediately that the midrange glare is gone. Gone too is that honky, boxy quality, and the tiring upper midrange screech that current production tubes are famous for. Here are some VERY GENERAL observations about some of these vintage tubes:

TELEFUNKEN, SIEMENS, VALVO, LORENZ, and other German made NOS: These tubes are usually characterized by an impressive open "air" at the top end. The soundstage is large, even in mono applications these tubes have a great 3-D image. The midrange is ruler flat, and the bass is tight and accurate. These tubes have a fine sense of dynamics, and most are impressively quiet. These are not "warm" tubes, and to some ears their lack of midrange warmth may be heard as bright. I tend to think of them as accurate, and their clean, focused sonic image is astonishing. My personal favorites. Check out Siemens longplates, Telefunken smoothplates, or Siemens E83CC for critical phono preamp or microphone preamp work. Same goes for the Telefunken "selected tube" and the tubes with blue tips that were intended for critical medical equipment. These tubes are dead quiet, ruler flat, laboratory grade beauties that will knock your socks off! The Siemens, Valvo, and Lorenz are often priced lower than the more well-known Telefunken, and can be a great bargain since their sonics are similar to the highly regarded Telefunken. Oh, and here is a little secret: the Telefunken ribbed plates sound pretty much the same as the smoothplates! In spite of the "shootouts", and "Some Guy's Tube Lore", and other claims to the contrary, the sonic differences between these two tubes (made in the same era at the same factory) are small (the rib plates are a bit warmer in the midrange) and very subjective. Don't let anyone tell you what tubes you should like and what you should not like!

AMPEREX, PHILIPS, MAZDA and other Holland/France/Belgium made NOS: These tubes are a great balance of a clean, airy top end, nice midrange warmth, and accurate bass. They are very pleasant, clean, and musical to listen to in hi-fi applications. Unlike other clean European tubes, these break-up impressively when overdriven in a guitar amp. Check out the Mazda 12AX7S silver plates for critical phono preamp or microphone preamp duties. These tubes are dead quiet, with a great sense of air and dynamics, with incredible speed and impact. The Philips Miniwatt series, usually made in the same Heerlen, Holland factory that produced the Amperex Bugleboy tubes, are a great alternative to the increasingly rare Bugleboy. They are identical internally, carry the same factory code markings, and sound the same. These Holland tubes can often be found, sometimes made for other brands or OEM labelled for amplifiers, when the Bugleboys cannot. The rare longplate versions are the same sonically, but with even more soundstage space and detail. The rare French Mazda has the air and sparkle of the Telefunken, the touch of warmth of the Amperex, and adds a nice bit of dynamic punch to the sound.

MULLARD, GENALEX, BRIMAR, and other British made NOS: Like a warm British jacket of the finest tweed, these glorious tubes have an attractive sweet warmth in their midrange and lower regions. The top end is silky and pleasant, without being rolled-off. The best of these tubes retain a fine sense of "air" at the top, and the upper midrange is smooth and liquid. These tubes reproduce the human voice, especially female voices, with haunting realism. The rare longplates and Genalex versions have an eye-popping huge soundstage, razor sharp focus and detail, and an uncolored top end while retaining the warmth of the lower priced versions.

RCA, RAYTHEON, GE, SYLVANIA, and other USA made NOS: This group is very diverse. The RCA, Raytheon, and Sylvania blackplates are among the best here. These are very musical tubes with air and sparkle at the top end, warmth in the mids, and great bass. The RCA are drop dead beautiful in guitar amps, even the lower priced greyplate and longplate versions. They also have a wonderful "phat" gritty sound when overdriven in these amps. The blackplates and most tubes made for organs are very quiet. The greyplate GE is an all-around nice-guy tube to listen to, the longplate here possibly getting the nod for hi-fi use. The Sylvania greyplate and military versions are clean and a bit bright, but the Sylvania 5751 variants are very balanced and pleasant to listen to for hours. The GE blackplate 5751 triple mica is also in great demand as a very musical vintage tube. The RCA 5751 is more like the Mullard, with a rich warmth and wide bandwidth. Currently, the USA made tubes are a nice surprise with their low prices as compared to the European types.

Shuguang 12AX7, The Chinese 12AX7 tube (made by Shuguang) is popular with Marshall owners for its gain and bite. It is currently re-branded by Penta, Ruby Tubes, Groove Tubes, and many others. Regardless of the name, they are all the same.
They seem to be improving the quality of these as production goes on.

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Post by Structo » Sat May 11, 2013 12:07 am

Tony (dorrisant) reminded me of a good website that sells NOS tubes and accessories, as well as good technical articles about vacuum tubes.

Brent Jesse Recording & Supply.

A good 12AX7 video "How to Spot Super Rare 12AX7 Vacuum Tubes part I" ... 6d-cZB7DgA

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Post by Structo » Sat May 11, 2013 5:30 pm


Don't let that smoke out!


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