Vacuum Tube: 02/01/2008

2/22/08

JJ E34L / EL34

JJ is the new name for the Teslovak (Tesla) tube company.

A good general purpose EL34. As previously mentioned, the sound is well balanced with tight bass response and great mids. Early on we had issues with mechanical noise however later stock has been much improved and noise is no longer a worry.

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Winged "C" / SED

If you want one EL34 tube that will do anything the Winged "C"/SED is money

well spent. There is ample bass response but it is firm and controlled. The mids are smooth and the top end shimmers. Nice swirling harmonic content. The construction of the tube is outstanding and I feel it contributes to the overall performance. Lots of clean headroom from this tube with a smooth transition into breakup. Probably great in home audio applications, but if you want raunch at lower volume levels keep reading.

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Svetlana EL34

The Svetlana is the perfect tube for classic rock. The midrange is very pronounced a

nd the high end is smooth. The bottom end response is not the best, but in a guitar amp it becomes a moot point. In the test amp the mids just rip through the mix. No guitar player is going to get lost in the mix using these bottles. These tubes deliver incredible crunch making them perfect for that ZZ Top, old EVH sound. Seven string down-strokers may not be as pleased because they don't have that crushing deep bottom end. (Note: the amp used for this review was done in a 100 watt Marshall JMP)

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Sovtek EL34WXT

Sovtek has come a long way with this tube since the EL34G. Construction has been improved greatly reducing mechanical noise. Very good sound but not in the same range as the Svetlana. It seems as if the frequency response has been shifted toward the midrange band. Harmonics are rich and fairly balanced but the high end can get a bit bright. Great in a darker sounding amplifier.

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Shuguang EL34-B

For many years no one would have believed that Chinese tube factories could turn out wo

rk of this quality. The construction of this tube is first class, with a well-supported plate structure that rests in a large straight bottle that tapers to a well finished brown base. These tubes represent a very solid piece of construction with almost no mechanical noise and an overall feeling of quality.The sound is loud and clear with a very nice sonic range. Not excessive in tops, mids, or bass, they are accurately described as well balanced. The sample tested had no audible microphonics and an average background noise level. Harmonic content was rich, lending that pleasant "swirl" and sustain that guitar players crave.

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JJ KT77

The KT77 has been gone for many years and original NOS pieces are rare and expensive. JJ electronics has revived

the design and released their own version. To my ears it sounds a lot like a 6L6 but has the heater current, max plate voltage and output rating of an EL34. The JJ KT77 has published specs that are identical to the original Genalex specs. The base has pin 1 included but there is no connection to any internal element. The sound is somewhere between an EL34 and a 6L6. Overall a nice balance of tone in bass, midrange and treble. The breakup is earlier than a 6L6 with more compression but not as compressed as the EL34. Unlike an EL34 this tube can be used in place of a 6L6 in Fender amps with minimal modifications. Vintage Fender amps usually use pins 1 and 6 as tie-off points for input grids and screen grids, mounting resistors on the socket. A standard EL34 can’t be plugged in because the input grid would be shorted to the suppressor grid via pin one. The KT77 avoids this. The only caveats are to ensure that your power transformer can supply an extra 500ma of heater current per tube and that the range of bias voltage adjustment is correct. If you have a Marshall amp and find EL34’s too compressed and 6550’s too crunchy the JJ KT77 may be just the ticket.

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Electro Harmonix 6CA7-EH

At last something to replace the hole left since the EI 6CA7 went out of stock. These tubes sound every bit as good as

the old EI tubes and are probably my favorite tubes for Hiwatt guitar amplifiers. It’s like they were made for each other. These tubes are like EL34’s on steroids. They handle high voltage and current without problems. As mentioned, there is nothing like a Hiwatt head powered by 6CA7 tubes and driving a 4x12 cab loaded with Fane speakers. This is classic rock tone at its finest. It’s the sound of Pete Townsend and The Who. The 6CA7 has more headroom than an EL34 and by the time you get it really crunchy sounding your pants are flapping in the breeze. Just the right amount of compression for great thick rock tone. Biasing levels can be dialed in from warm to hot without causing significant tonal changes. The EH is well constructed and should not pose any noise problems. If using these tubes in more reasonable systems the EH 6CA7 is capable of some really nice clean tones thanks to that extra headroom. If you want early Van Halen, these are not the tubes for you. If you want something loud and proud, you want to put the EH 6CA7 in your amp.

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EL34 Tube Type Review

Review Notes
Tube reviews written by John Templeton.

It’s not easy evaluating something as subjective as sound. We each have our own personal taste in music and the way it sounds. I have attempted to add some objectivity by defining some aspects of tube performance that affect any listener, regardless of application, budget or musical taste. The EL34 is a very popular tube and is used in equipment that creates as well as reproduces music. This testing was done using tube guitar amplifiers. With this in mind, consideration has been given to construction quality and mechanical noise. These factors are important to musicians but may not be an issue when a tube is used in the home or studio.

Test Amps:

1973 Marshall Super Lead model 1959 This amp is completely stock using NOS pre-amp tubes. The sound was reproduced through a 1971 Marshal cabinet with 4 Celestion G12M "greenback" speakers.

Class A Combo Designed and built by Bernard Raunig. This is a true single ended class A amplifier, using a 5Y3 rectifier and a single 5691 pre-amp tube. With a volume and single tone control this amp really lets you hear the tonal differences between the tubes.

EL34 comparison at a glance

Rated 0 - 5 where 0 is Poor and 5 is Excellent

Rows in gray are tubes used for reference

Electro Harmonix 6CA7-EH

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2/21/08

Tesla / JJ EL84

This tube has been a personal favorite of mine so the review is not entirely unbiased. With the JJ you seem to get a compromise between tone and reliability. Nice mids, sparkling highs and solid bottom end characterize this tube. From a construction standpoint I think JJ has hit the mark. As with any EL84 they can be prone to mechanical noise in combo amps. However, they seem to take the heat and vibration in stride without any negative tonal effects. In the AC30 the JJ tubes really delivered the VOX chime with lots of swirl and shimmery harmonic content. In the little Pro Junior just crank it up and you get a great, nasty, overdriven sound. That’s not bad, it’s good. When pushed hard into the land of the square wave they remind me a lot of a good 6V6. If you have tried the OEM Sovtek’s that shipped in your amp it’s worth your time to try a set of JJ EL84’s. Many convert and never go back. In cathode biased amps you can generally plug and play for that hot creamy “woman tone” that so many desire.

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TAD EL84-STR

The STR designation tells us that this was a Special Tube Request by the Tube Amp Doctor. In all honesty it looks and sounds like a pretty radical take on the EL84. The dimensions of this tube deserve your attention. Most tubes made in the U.S., England and Germany were built to a standard size. I often compare the new breed of EL84’s to the 1964 G.E. Essential Tube Characteristics Handbook. The TAD EL84STR is about a quarter inch shorter than any EL84 on the market and falls below the minimum GE spec of 2.344 inches. You may have to modify or adjust spring and clip type retainers for the shorter bottle. These are beefy bottles as well, with a measured maximum width of .874 inches. The GE specification is a maximum value of.875 inches. The TAD EL84STR also has the largest plate structure of any EL84 you can buy. I won’t give any more specs. Just trust me on this one, it’s enormous! There is very little clearance between the plate and the bottle and they get hot! This tube has the deepest bass, the highest highs and strident mids. In short, they sound a lot like a premium 6V6. No smooth creamy distortion here but tons of rock and roll crunch. If your bored with your normal EL84 tone these are definitely tubes to consider. Not recommended for some VOX amps as well as some smaller Mesa Boogie amps due to size issues.

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Russian EL84M

Some people will swear that the “M” stands for military but I’m not convinced. They look pretty much the same on the outside as normal Sovtek ‘84’s but there has to be something extra happening. The M’s seem less prone to mechanical noise and will do much better at surviving the VOX torture test. I loaded up the AC30 with a quad of EL84M’s and found that they could be run for a couple of hours without overheating. The Heat/Cool cycle still has some affect on life but the 84M lasted longer in this environment than the standard fare. A good choice if you have a cathode biased amp or like your tubes biased to more than 70% of idle dissipation.You do pay a sonic and financial price for the EL84M. They are more expensive than the standard EL84 but will last longer. Sonically they are a bit of a different animal. People refer to them as sounding stiffer or more strident with more headroom and may not like the breakup characteristics when pushed. It is really a personal judgement call. If standard EL84’s have been a problem due to heat or noise and you find they don’t last as long as you would like, try the EL84M and see what you think of the tone. In my opinion they are worth the extra money for reliability and the tone is still classic EL84.

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Sovtek EL84

- The Sovtek EL84 has been a staple for Fender, Boogie, Crate, Peavey and other manufacturers of tube amps using the ’84. This tube really is a good value. It is predictable, reliable and affordable. You can get good EL84 tone at a reasonable price. The Sovtek EL84 has been around a long time, and it has shown continuous improvement over the years. Using a matched set of properly biased tubes will yield a clear smooth sound that is fairly warm and transitions into a smooth breakup with that singing tone that EL84’s are known for. In cathode biased amps like the VOX they get a premium workout and will suffer some effects from heating and cooling. Being prone to mechanical noise in a combo amp, the EL84 is not recommended for amps with poor air circulation. The heating/cooling cycle inside an AC30 easy-bake oven seems to loosen up the mechanical structures within the tube causing them to become very noisy (mechanically) with time. This is true of any amp that uses an EL84 in a poorly ventilated chassis/cabinet arrangement, so if this is your rig, go for the JJ or Russian EL84M.In the Fender Blues Junior the tubes can really put out respectable volume and great tone for all types of music. The highs are not harsh, the mids are warm and the bottom end is not lacking. If you want to really scream try a Pro Junior with full volume. Very crunchy yet smooth with great singing sustain. I personally like my tubes biased at 60% or 70% of static dissipation and the Sovtek EL84 performed well in this range.

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Electro Harmonix EL84-EH Review

For most applications this is a good bet. The sound of these tubes is very smooth when biased correctly. Tonally, it’s hard to go wrong. They are pleasant to listen to and have the creamy overdrive most people look for in an EL84. They have a nice chime but it’s not overbearing. It looks a lot like the standard Sovtek but a closer inspection will reveal differences. The plate looks a bit more polished with a different coating and internally they feature precisely wrapped grid wires with a bright metal shine. The only problem with this tube is that like the Sovtek and TAD product, they are tubby. The fattest one I measured was .886 inches thick against the G.E. maximum width spec of .875 inches. For most purchasers this will not be an issue. If you have an amp that requires the tube to pass through a hole in the chassis before the pins seat in the socket you should measure the diameter of that hole. If you’re still unsure, the JJ EL84 is the closest in dimensional specs to NOS measurements and the G.E. standards for the 6BQ5.

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2/19/08

Ei 12AX7 Review.

This tube should win an award for best and worst in class. The first one I tried squealed in the combo amp and produced a ringing sound in the half-stack. (Remember these were not from the pre-screened tubes that thetubestore.com sells.) The second one I tried was fantastic. There were no microphonics problems with this second tube. The scores for microphonics (2 and 4) are for each individual tube that was tested. A few phone calls to another tech confirmed my suspicion: there is a high failure rate when initially screening these tubes for microphonics. The ones that do pass testing are wonderful; they are very musical sounding with lots of gain and a very low noise floor. When playing the guitar you could really get the benefit of their dynamic range. They can reproduce soft passages accentuated with a sharp punch and you don't have to go near the volume controls. I'm keeping the test tube for some long term testing. These would be great tubes for home audio applications. Due to the microphonics problem, I'm unsure as to their roadworthiness. At home or in the studio, they will deliver great results. The only caveats are; make sure they are carefully screened and don't think about using them in high gain combo's unless they are tested in a similar amp first.

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Tesla / JJ 12AX7 / ECC83-S Review.

This tube sports a different plate design than found in most 12AX7's. When you look at them you can't help but think that they must be rugged and good for the musician on the road. The compact plate structure does nothing to dampen their sound or dynamic response. I find them to be well balanced. While not as harmonically rich as others I tested, they do provide high gain without the usual noise and microphonic problems you would expect. This is great sound for your dollar. If you're using a combo amp and find the Philips a little rich sounding, the JJ ECC83 may be your solution.

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JAN-Philips 5751 Review.

While not really a 12AX7, it shares the same pin-out arrangement and is designed for less gain in favor of lower noise and microphonics. It worked well in both test amps and can be used to advantage if your amp has too much grind. One of these should calm things down a bit. The 5751 is an affordable alternative to the 12AY7 used in original Fender tweed amps and can be subbed for a 12AT7 like a reverb driver tube. In this application, you will get good gain with a warmer sound than the 12AT7. The even balancing makes them a nice phase inverter and allows you push the front end of the amp a little harder.
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JAN-Philips 12AX7WA Review.

If you really want NOS (New Old Stock) tubes, this is one of the best buys out there. The Philips tube is well built and should be long lasting. The tubes I tested had lots of gain while still maintaining very good noise levels and good tolerance for microphonics. The tone was solid in the midrange with very wide dynamic response. If you're not careful with your setup, you can get these tubes to be boomy in the bottom end and shrill in the high end. I found that they were great with the tone controls set flat. Great in both combo amps and monster stacks.

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Sovtek 5751 Review.

The Sovtek 5751 is an affordable alternative to the 12AY7 used in original Fender tweed amps and can be subbed for a 12AT7 reverb driver tube. In this application, you will get good gain with a warmer sound than the 12AT7. The even balancing makes them a nice phase inverter and allows you push the front end of the amp a little harder. If you wish to use a 5751 in a 12AX7 position to reduce gain we recommend you use the JAN-Philips 5751 tube.
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Sovtek 12AX7-LPS Review.

This is an entirely new design from Sovtek and a great step up in sound quality. They have very large ribbed plates and great sound reproduction. I found them very smooth and well balanced in terms of bass, mids and treble response. The large plates make them more prone to microphonics and in combo amps, so they can be a problem if you like to run things wide open. It is still the best thing Sovtek has produced in a 12AX7, with very good gain and low noise. I would advise against using them in compact high-powered combo amps where they will be subjected to lots of vibration. One other note about the construction of these tubes is they have filaments that are almost completely encased in the plate structure. They often don't "light up" when working properly. This is not a problem, it's normal for the LPS.

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Sovtek 12AX7-WA, 12AX7-WB Review.

I've grouped these two together because they have essentially the same sound. The only noticeable difference between the two was a bit more gain from the WB model. These tubes are rugged little brutes, and that's probably why they are OEM components for many major amp makers. Both tubes could be whacked with a stick at full volume and not show much in the way of microphonics - but DON'T DO THIS AT HOME, as it is often a destructive test for tubes. They don't have the best sound in this type, being prone to the occasional pop or tick. The sound quality lacked any real character but was acceptable. If the budget is tight, their affordability will be attractive. Also, keep in mind that many amp designers design the equipment to sound best with the tubes they will use in production. I have a friend that claims his amp only sounds right using Chinese pre-amp tubes, but your mileage may vary on this issue. If you like the Sovteks then go for it, particularly if you will use them in high gain applications with lots of effects.

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Electro-Harmonix 12AX7 Review.

These are not relabelled Sovtek 12AX7-LPS tubes. There is a marked difference in construction and performance. The 12AX7 EH has a nice balanced sound, fairly low noise floor and excellent performance in terms of microphonics. The lack of microphonics may be in part from the return of the shorter plate structure or materials. I've had some samples that were tried in various amp stages. Pre-amps, tone stacks and phase inverters, a winner in every location, although I like to use a 12AT7 for reverb circuit drivers due to their lower gain rating (just a personal preference of mine). I have used the EH to successfully tame amps that defied all other attempts to kill microphonics and unwanted feedback. This tube is a winner, buy 'em and try 'em, they may be just the piece you've been looking for.

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Mullard 12AX7 / ECC83 Reissue Review.

This is a nice tube but in my opinion better suited to home audio than guitar amps. The tubes have well balanced triode pairs and a very even flat response. Compared to a Tung Sol it sounds a bit flat, but so does a NOS Mullard. Microphonics are not an issue despite the larger that average plate structure. The transconductance on my sample was the same as two NOS samples I measured. Not really high gain at all, but a real good noise floor and a nice smooth tone that doesn’t encourage ear fatigue the way some preamps can be. The Tung-Sol 12AX7 is my favorite preamp for guitars because it accentuates highs and lows. The Mullard adds virtually no tone coloring and is smoother sounding to my ear that a JJ ECC83S. For hi-fi gear the Mullard will likely be a winner but there are better choices for guitar amps for less money.
Informaition from thestoretube.com

Tung-Sol 12AX7 Reviews

There are only so many ways to describe tube tone and most have become clich้'s. The Tung-Sol 12AX7 has the gain and drive of a Chinese 12AX7 and the pure tone of a Mullard or Brimar from the U.K. I've had two people come to me recently with amps they thought were in need of complete overhauls. In both cases, careful examination revealed no serious problems and all the tubes "tested" as good. At the end of the day, I replaced the NOS Mullard and RCA pre-amps (one in each amp) with a reissue Tung-Sol 12AX7. In both cases the owners were very impressed and thought that their amps had been restored to full health. Believe it or Not.

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12AX7 Tube Type Review

Review Notes Guitar Amp Tube Reviews written by John Templeton.
The tubes used in this review were selected at random from thetubestore.com's inventory of untested tubes. For each tube used in the test, two were taken since there was no pre-screening involved. The aim was to get a sample that would be practical to work with but allow for variations in the tubes or prevent picking the only dud in a lot.The test amplifiers used were very different. One was a 100-watt Trace Elliot Speed King with 4 x 12 cabinet, and the other was a Fender Blues Junior combo amp. This allows the high power, high gain crowd and the more conservative players to get the fairest evaluation possible. Some tubes were clearly better suited in one application or usable in both. All tubes were used at the input amplifier stage of the amp since this seems to be where most people develop their perceptions of how good a pre-amp tube is.

What Makes A Good Tube? The musical detail or ability to reproduce the sound of the instrument is a key factor in assessing a tube for guitar amplifiers. There is no perfect tube available. Each one has strengths, weaknesses and certain factors that contribute to its overall ratings. Usually a compromise is arrived at in the search for premium tone. All tubes will exhibit some degree of microphonics. Microphonics do not mean that a tube is unusable. You just have to screen them a little closer and determine where they are best suited for use. Input pre-amps are the most sensitive areas of the amplifier. When used in this application most tubes will generate some noise if you tap on them with a pencil during operation. Keep in mind that doing so can actually damage the tube and make it more microphonic or cause it to fail if you hit it real hard. Although they are screened prior to shipment a tube is an electromechanical device and can be damaged during shipment. A microphonic tube will ring, howl or produce general feedback problems. It will be more noticeable at louder volumes or when used in close proximity to a speaker, typically in combo amps. If the tube has good tone at lower volumes and is free from unwanted noise, you use it in a less sensitive part of the circuit, such as tone recovery or phase inverter applications.

Noise is more of a problem than microphonics. A noisy tube will make random popping noises, crackle occasionally or just hum. All tubes have a certain noise floor; this is the inherent background noise that the tube makes in operation. Typically, you will notice this as a soft hiss or "white noise". Tubes designed for high gain can exhibit more background noise. Other components can cause noise problems that may be blamed on a bad tube. Plate resistors are notorious for causing hiss and crackling as they age and begin to fail. A new tube may better amplify these defects, so try substituting another new tube to be sure of the source of the noise.

12AX7 comparison at a glanceRated

0 - 5 where 0 is Unacceptable and 5 is Excellent

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6P1P

The 6P1P (Russian: 6П1П) is a Soviet-made miniature 9-pin beam tetrode vacuum tu be with ratings similar to the 6AQ5, EL90 and the 6V6. Because of a different pinout (a 9-pin base versus 7-pin base) than an 6AQ5/EL90, it cannot be used as a plug-in replacement for these types, however, it will work in the same circuit with component values unchanged. Its maximum plate/screen voltage and dissipation ratings are actually slightly higher than a 6AQ5. A ruggedized/extended ratings version of the tube is designated 6P1P-EV (Russian: 6П1П-ЕВ) roughly equivalent to the 6AQ5W. A Chinese-manufactured version of the tube also exists, labeled 6P1.
The type was commonly used in Soviet-built vacuum tube radios and TV sets as an output audio amplifier, until it was replaced by the higher-performance 6P14P (EL84) tube.
The tube is no longer believed to be in production.
Also see 6AQ5, 6V6 and Russian tube designations.

From Wikipedia, the free encyclopedia

6N3P

The 6N3P (Russian: 6Н3П) is a Russian-made direct equivalent of the 2C51 vacuum tube. It is slightly larger in size than the American tube.
6N3P was widely used for FM band radio input unit stages (nearly all 1960s Soviet radios with FM band all employed the same input unit on a separate subchassis). Currently, it has some use in DIY preamps. A ruggedized/industrial version of the tube is designated 6N3P-EV (Russian: 6Н3П-ЕВ

From Wikipedia, the free encyclopedia

6N2P

The 6N2P, (Russian: 6Н2П) also sometimes spelled in English "6H2Pi" is a miniature 9-pin dual triode vacuum tube manufactured in USSR, Russia and China with characteristics similar to the RCA 12AX7. The most significant difference between the two is that 6N2P has its two filament elements connected in parallel, unlike the series filament connection of the 12AX7, and it is thus only possible to operate it from a 6.3 volt, 300 mA filament supply (whereas a 12AX7 may be operated from either 6.3 or 12.6 volts.) The 6N2P also has slightly lower gain than a 12AX7.

In the 1970s an improved and more rugged version of the 6N2P was introduced, designated 6N2P-EV (Russian: 6Н2П-ЕВ) Currently, a 12AX7 variant derived from the 6N2P-EV is being produced by Sovtek, under the designation 12AX7WA.
A Chinese version of 6N2P exists, labeled in Latin lettering (instead of Cyrillic) 6N2.
In the 1990s a (now extinct) line of "Red Bear" guitar amplifiers was being produced in Russia by Novik Ltd. and distributed in the United States by Gibson Guitar Corporation. These amplifiers used 6N2P tubes instead of the much more common 12AX7, prompting user modifications of the amplifier to 12AX7, because the original Russian 6N2P was scarcely available outside of Russia.
On the photo, from left to right - 6N2P produced in USSR in 1967, 1974, 6N2 produced in China and Soviet 6N2P-EV (left), produced in 1980.

From Wikipedia, the free encyclopedia

6N1P

The 6N1P (Russian: 6Н1П) is a Russian-made miniature 9-pin medium gain d

ouble triode vacuum tube intended for use as a line audio amplifier and cathode driver.
Basic data: Uf = 6.3V, If = 600 mA uM = 35 Ia = 7.5 mA S = 4.35 mA/V Pa = 2.2 W
The 6N1P has similar ratings to the 6DJ8 and in the past was sometimes rebranded as such, however, because of the differences between the two types (such as twice as high filament current of an 6N1P and three times smaller S value) it's not suitable as a direct replacement in 6DJ8 applications and vice versa.
A ruggedized/extended ratings version of the tube is designated 6N1P-EV (Russian: 6Н1П-ЕВ)
It has currently found a use as a driver tube in hi-fi tube amplifiers (such as Audio Research models VS55 and VS110) because of its excellent low distortion and low noise characteristics. The tube is being manufactured by "Voshod" plant in Kaluga, Russia (see [1]) and is being distributed in the West under the Sovtek and Svetlana brand names.

From Wikipedia, the free encyclopedia

2/15/08

6V6

6V6 is the designator for a vacuum tube introduced by Radio Corporation of America RCA United States

in late 1937.
6V6 is a beam-power tetrode, similar to its predecessor the 6L6. While the 6L6 was an excellent tube, it was not considered suitable for use in home consumer electronic devices at the time because its output, especially in a push-pull pair, was so high. With the introduction of the lower-powered 6V6, which required only half the heater power of the 6L6, the beam-power tetrode became a usable technology for the home, and began to see common use as the audio output stage of radios and other electronic home entertainment devices where standard power pentodes such as the 6F6 had previously held sway. The 6V6 required less heater power and provided less distortion than the 6F6, while still offering higher output in both single-ended and push-pull configurations.

History

The 6V6 was introduced in both metal and shouldered glass tubes. RCA w

as promoting the superiority of its metal tube designs in the second half of the 1930s, and this tube, having been introduced during that period, was produced in large quantities in this format. Other tube manufacturers also produced the 6V6 in glass tubes, which were commonly found in radios not made by RCA. By 1940 the 6V6 was mostly being produced in a smaller "GT" glass envelope, and later the 6V6GTA was introduced which had a controlled warm-up period.

Current use

Generally 6V6 tubes are sturdy and can be run beyond their published specifications, except for the 6P6S, which has poor tolerance for out-of-spec operation versus most American and West European-made 6V6 variants. Because of this, the 6V6 became very popular for use in instrument amplifiers. This market allows Chinese, Slovakian and Russian tube factories to keep the 6V6 in production to this day. It is very often used in guitar amplifiers

Similar tubes

A similar tube is 6AQ5, which has similar specifications to the 6V6GT, but in a miniature glass shell, and the 7408 as well as the Soviet-produced 6P1P, which is essentially the same as 6AQ5, but has a 9-pin base.
In the Soviet Union a version of the 6V6GT was produced since the late 1940's which appears to be a close copy of the 1940s Sylvania-issue 6V6GT - initially under its American designation (in both Latin and Cyrillic lettering), but later, after USSR had adopted its own system of designations, the tube was being marked 6P6S (6П6С in Cyrillic.)

From Wikipedia, the free encyclopedia

6SN7

6SN7 is a dual triode vacuum tube, on an 8 pin octal base. Although the 6S-- series tubes are often metal cased, the 6SN7 is generally found only in a glass GT size envelope. The 6SN7 is basically two 6J5 triodes in one glass envelope.

History
Originally released in 1939 it was officially registered in 1941 as the glass-cased 6SN7GT. During World War II a 6SN7A was developed as a slightly improved version, then also a more rugged 6SN7W f

or military use.
With the advent of television the 6SN7 was well suited for use as a vertical-deflection amplifier. As screen sizes became larger, the tube started to have marginal voltage and power headroom. To address this, upgraded versions GTA (General Electric, 1950) and GTB (GE, 1954) were made with higher peak voltage and power ratings. The 6SN7GTA has anode dissipation uprated to 5.0 watts "design center rating". The 6SN7GTB is identical to the 6SN7GTA except for a controlled heater warmup time, for use in Television sets with 600ma series heater strings.
The 6SN7 has a 6.3 V 600mA heater/filament. The 12 volt filament equivalent is the 12SN7GT or 12SN7GTA. (12.6V 300mA filament) There was also a comparatively rare 8SN7 (8.4V@450mA filament intended for 450mA series string TV sets)
Numerous other variations on the 6SN7 type have been offered over the years, including 7N7 (Sylvania 1940, loktal-base version), 5692 (RCA 1948, a super-premium version with guaranteed 10,000 hour lifetime), 12SX7 (RCA 1946, intended for use in 26-volt aircraft electronics), 1633 (RCA 1941, also for 26-v radios), 6042 (1951, another 1633 type),

and 6180 (1952). American military designator for the 6SN7GA was VT-231, and the British called it CV1986 or CV1988. European designators include ECC32, 13D2 and B65. Each of the giant SAGE computer systems used hundreds of 5692s as flip-flops.
While often used as an audio amplifier in the 1940-1955 period, usually in the driver stages of power amps, the 6SN7 was also very popular in television vertical sweep applications. The designer of the famous Williamson amplifier, one of the first true high-fidelity designs, suggested use of the 6SN7 since it was similar to the British triodes that he used in his circuit. In most late-1950s applications it was replaced by the 12AU7, then by transistors in the 1960s.
6SN7s are still manufactured in Russia and China under the old Soviet designator 6N8S, and continue to be used in some modern tube high-fidelity equipment.
The 6CG7 is a miniature tube (RCA, 1951) that has very similar ratings. It was also made as an 8.4V 450ma series string type as the 8CG7.

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6N3P

6L6(EL37)

6L6 is the designator for a vacuum tube introduced by Radio Corporation of America in July 1936. At the time Philips had already developed and patented power pentode designs, which were fast replacing power triodes due to their greater efficiency.

History

The 6L6 is a

descendant of the "Harries Valve" developed by British engineer J. Owen Harries and marketed by the Hivac Co. Ltd. in 1935. Harries is believed to be the first engineer to discover the "critical distance" effect, which maximized the efficiency of a power tet rode, by positioning its anode at a distance which is a specific multiple of the screen grid-cathode distance. This design also minimized interference of secondary emission electrons dislodged from the anode.
EMI engineers Cabot Bull and Sidney Rodda improved the Harries design with a pair of beam plates, connected to the cathode, which directed the electron streams into two narrow areas and also acted like a suppressor grid to absorb some secondary electrons. The beam design was also undertaken to avoid the patents which the giant Philips firm held on power pentodes in Europe. Because this overall design eliminated the "tetrode kink" in the lower parts of the tetrode's voltage-current characteristic curves, which sometimes caused tetrode amplifiers to become unstable, MOV marketed this tube family under the sobriquet "KT", meaning "kinkless tetrode".
Because MOV's engineers did not feel the kinkless tetrode could be successfully mass

-produced, they licensed the design to RCA. This proved to be a poor business decision on MOV's part. RCA subsequently had enormous success with the 6L6. It replaced the use of power triodes in public-address amplifiers almost overnight. So many applications were found for the 6L6 that a complete list would be impossible to assemble. MOV introduced their version, the KT66, a year later.

RCA's first version had a metal-canister shell rather than glass — being one of the early octal base tubes, most of which were marketed as having metal shells. Later versions, including the 6L6G, 6L6GA, 6L6GB, 5881, 5932, 7027, and the final version 6L6GC had glass envelopes, which made radiation cooling of the anode easier. The voltage and power rating of the 6L6 series was gradually pushed upwards by adding features such as a micanol base, thicker plates, thicker grid wires, grid cooling fins, and special ultra-black plate coatings. The original metal version was rated for 19 watts dissipation, while the later 6L6GC is usually rated for 30 watts.

Variations

Early variations included transmitting tubes such as the 807 (1937), the smaller 6V6 (1937), the many KT versions marketed in Europe, and a subsequent vast array of audio and RF power tubes. One of the largest post-WWII applications was in the basic design of television sweep power tubes, starting with the 6BG6 (1946), a modified 807. TV sweep tubes were not replaced by transistors in earnest, until the 1970s.
Further testimony for this device's success would be even simpler: the 6L6GC version is still being manufactured and is used, primarily, in guitar amplifiers. Manufacture continues in Russia (2 factories), China (2 factories), Slovakia and Serbia. Thus, the 6L6 has enjoyed one of the longest active lifetimes of any electronic component at more than 70 years.

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6DJ8

The 6DJ8 is a miniature 9-pin medium gain dual triode vacuum tube. It is distinguished by its very high transconductance, mostly the result of its frame grid construction.

Origins

Developed by Amperex in 1958, the 6DJ8 was originally designed for use as a low-noise amplifier in VHF and UHF TV tuners, an improved successor to the usual 6BK7. But its high gain won it many designs in high-end test equipment. Most high-quality oscilloscopes from the 1950's thru the 1960's have many 6DJ8's tubes, often a majority.

Audio

Although not originally designed for the purpose, it became popular in hi-fi audio amplifiers. European-produced version of the tube is designated ECC88. An industrial (improved/higher ratings) version of the tube is designated 6922. New Old Stock (NOS) 6DJ8s and ECC88s produced in the past by major American or West European vacuum tube manufacturers (such as Phillips or Amperex) remain extremely popular with and highly sought by audiophiles. A version (direct equivalent) of this tube was also produced in the Soviet Union under the designator 6N23P (Russian: 6Н23П) and in China, under the 6N11 designator.
The tube is currently being produced in four versions in Eastern Europe - Slovakia by JJ Electronics (ex-Tesla), Serbia (Ei) and in Russia - 6DJ8 for Sovtek and 6922 for Electro-Harmonix.

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6CA7(EL34)

The EL34 is a vacuum tube of the pentode type. It has an octal base (indicated by the '3' in the part number) and is found mainly in the final output stages of amplification circuits. The American RETMA tube designation number for this tube is 6CA7. Russian analog is 6p27s (Cyrillic: 6п27с

Specifications

In common with all 'E' prefix tubes, using the Mullard-Philips tube

designation, the EL34 has a heater voltage of 6.3V. It is capable, when used at its plate rating of 800 volts maximum, of producing 90 watts output in Class AB1 in push-pull configuration.
Unlike the 6L6, (EIA base 7AC) the EL34 has its grid 3 connection brought out to a separate Pin (Pin 1) (EIA base 8ET) and its heater draws 1.5 Amps compared to the 0.9 Amp heater in the 6L6. The EL34 was generally built as a true pentode, while the 6L6 was built as a beam tetrode which RCA often referred to as a beam power tube.
The EL34 is still in production by JJ Electronic, Svetlana and Sovtek, amongst others. Some firms make a related tube called an E34L which is rated to require a higher voltage bias on the grid, but which may be interchangeable in some equipment.

Application

The EL34 is commonly used in high end guitar amplifiers, it is characterized by a greater amount of distortion at lower power than other octal tubes such as a 6L6, KT88 or 655 0. The EL34 is found in many British guitar amps and thus is associated with the "British Tone" (Marshall) as compared to the 6L6 which is generally associated with the "American Tone" (Fender).

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EL84

The EL84 (European designation - known as the 6BQ5 in North America) is a vacuum tube (a.k.a. valve) of the power pentode type. It has a 9 pin miniature base and is found mainly in the final output stages of amplification circuits, most commonly now in guitar amplifiers, but originally in radios and many other devices of the pre-transistor era.

It was developed to eliminate the need for a driver tube in radios, and has rather more gain than is usual in a power pentode, producing full output from a relatively small drive signal. This eliminated the need for one preamplifier triode in radios, making them cheaper to produce. As the EL84 itself is a 9 pin miniature, it was also cheap to produce and manufacturers were quick to adopt it in general use, and they are found in many old European valve radios.
In common with all 'E' prefix tubes, using the Mullard-Philips tube designation, it has a heater voltage of 6.3V. It is capable, when used at its plate rating of 300 volts maximum, of producing 17 watts output in Class AB1 in push-pull configuration.
Developed by Philips in 1953 for use in the British Mullard 5-10 amplifier, the EL84 came to prominence when used in Watkins (and later the Vox) amplifiers preferred by many British invasion bands of the 1960s. When overdriven, the EL84 power tubes of these amplifiers produce a distinctive chiming, articulate, treble-heavy sound when compared to 6L6 tubes more commonly used in American amplifiers of the era such as those from Fender.
Other equivalent tubes are the 7189, an extended-ratings version of the tube for industrial applications and the 6P14P (Cyrillic: 6П14П) produced in the USSR by the Reflektor plant, which is a direct equivalent of EL84/6BQ5. A slightly modified version of the 6P14P is currently being manufactured in Russia for Sovtek. An extended-ratings version of the 6P14P is also available - 6P14P-EV (Cyrillic: 6П14П-ЕВ) and is known among US guitar players as "EL84M" or the "Russian military EL84". While not necessarily a true "military version" of the tube (in fact it is more comparable to the 7189), 6P14P-EV are known for their low noise and durability. Large NOS (New Old Stock) supplies of the tube are available.
Current production of the tube takes place in Russia (Sovtek and Electro-Harmonix brands), Slovakia (JJ Electronics), and Serbia (Ei). The Sovtek EL84 is often sold under their own brand name by other well-known electric guitar and guitar amplifier manufacturers - such as Fender or Mesa Boogie.

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6AQ5

The 6AQ5 is a miniature 7-pin output pentode. The ratings are very similar to the 6V6 at 250V and is commonly used as an output audio amplifier in tube TV's and radios. It is also known under its Mullard-Philips tube designation EL90. A version of the tube with extended ratings for industrial application is designated 6AQ5A and 6005W.
Other close or equivalent tube types are: 6HG5, 6HR5, N727, CV1862 and the Tesla 6L31.
Also see 6V6 and 6P1P. Note: The 6P1P has a 9 pins and will NOT fit the 6AQ5 7 pin base.

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5Y3

The 5Y3 is a medium-power directly-heated rectifier vacuum tube introduced by RCA in 1935. It has found wide use in tube radio

s and early guitar amplifiers (of the Fender Champ type.) It is virtually identical, electrically, to the 4-pin type 80 tube, but with an octal base.
The success of the 80 and 5Y3 led to the development of many similar rectifier tubes of both higher and lower power ratings, including the 5V3, 5W3, 5X3, 5Z3, 5U4, and 5Z4. The epitome might have been the 3DG4 of the 1960s, with a full 240 milliamp capability.
Currently, a plug-in replacement is being manufactured by Sovtek in Russia, which is has very similar specifications, but is indirectly-heated, and can support currents up to 144 mA, versus the 120 mA of the original. However the Sovtek 5Y3 is not a true 5Y3. It drops less voltage than vintage 5Y3's, and may cause voltages to run too high.

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300B

The 300B is a directly heated power triode using a four pin base, introduced by Western Electric in 1937 to amplify telephone signals. It measures 6.4 inches high and 2.4 inches wide. It has a 40 watt anode dissipation. In the 1980s the 300B was rediscovered by audiophiles for use in home audio equipment and is known for its high fidelity, low noise and reliability. It is frequently used in single-ended triode (SET) audio amplifiers such as the Cary CAD-1610-SE and the Cayin A-300B.
Due to their rarity and high demand, new old stock (NOS) 300B tubes made by Western Electric from the 1940s–1960s have become collectible items among audio enthusiasts, with price tags in excess of $700 and used tubes selling for over $400.
Current manufacturers of new 300B tubes, and various workalikes include Electro Harmonix, Emission Labs, JJ Electronic, KR Audio, Sophia Electric, Sovtek, Svetlana and Westrex Corporation (which produces a "recreation" of the original Western Electric tube[1]). Prices range from $175 to $900 per matched pair.

From Wikipedia, the free encyclopedia

2/14/08

1L6

The 1L6 is a 7 pin miniature vacuum tube of the pentagrid converter type. It was developed in the USA by Sylvania. It is very similar electrically to its predecessors, the Loktal based 1LA6 and 1LC6. Released in 1949 for the Zenith Trans-Oceanic shortwave portable radio, this tube was in commercial production until the early 1960s .
The 1L6 was to be a specialty tube, produced in small quantities by very few manufacturers, mostly Sylvania for use by just a few manufacturers of shortwave portables, such as Zenith - in their Trans-Oceanics - and its short-lived rivals, such as the Hallicrafters TW-1000 and the RCA Strat-O-World and very few others.
Despite the limited application for 1L6, today NOS examples bring relatively high prices. Many radio collectors overcome this expense by using the more commonly available 1R5 with pin 5 cut off.

From Wikipedia, the free encyclopedia

2/12/08

American designation (with European equivalents)

0
0Z4 - Full-Wave Gas Rectifier

1 Volt heater/filament tubes
1L6 - Pentagrid converter

2 Volt heater/filament tubes
2B7 - Twin-diode remote-cutoff pentode

5 Volt heater/filament tubes
300B - 40 Watt directly heated triode
5Y3
5751 - low voltage low-noise avionics tube

6 Volt heater/filament tubes
6AQ5 - (EL90)
6AU6A - (EF94)
6BQ5 - (EL84)
6C19
6CA7 - (EL34)
6CL6 - Power pentode
6DA6 - (EF89)
6DJ8 - (ECC88)
6J5
6L6 - (EL37)
6N3P
6SK7 - Remote-cutoff pentode
6SN7 - Medium-mu twin triode
6V6 - Beam power tube (see also: 5V6 and 12V6)

12 Volt heater/filament tubes
12AT7 - High-mu twin triode (ECC81)
12AU7 - Medium-mu twin triode (ECC82)
12AV6 - Twin diode/High-mu triode (see also: 6AV6)
12AX7 - High-mu twin triode (ECC83)
12BA6 - Remote cutoff pentode (See also: 6BA6)
12BE6 - Pentagrid converter (See also: 6BE6)
12DT6 - Sharp cutoff pentode

25 Volt heater/filament tubes
25L6

50 Volt heater/filament tubes
50B5 - Beam power tube
50C5 - Identical to 50B5 except for biasing arrangement (HL92)
50L6 - Beam power tube (see also 25L6)
50HK6 - Power pentode

Field emitter vacuum tubes

In the early years of the 21st century there has been renewed interest in vacuum tubes, this time in the form of integrated circuits. The most common design uses a cold cathode field emitter, with electrons emitted from a number of sharp nano-scale tips formed on the surface of a metal cathode.
Their advantages include greatly enhanced robustness combined with the ability to provide high power outputs at low power consumptions. Operating on the same principles as traditional tubes, prototype device cathodes have been constructed with emitter tips formed using nanotubes, and by etching electrodes as hinged flaps (similar to the technology used to create the microscopic mirrors used in Digital Light Processing) that are stood upright by a magnetic field.
Such integrated microtubes may find application in microwave devices including mobile phones, for Bluetooth and Wi-Fi transmission, in radar and for satellite communication. Presently they are being studied for possible application to flat-panel display construction.

Information from Wikipedia.

Other vacuum tube devices

A vast array of devices were built during the 1920–1960 period using vacuum-tube techniques. Most such tubes were rendered obsolete by semiconductors; some techniques for integrating multiple devices in a single module, sharing the same glass envelope have been discussed above, such as the Loewe 3NF. Vacuum-tube electronic devices still in common use include the magnetron, klystron, photomultiplier, x-ray tube and cathode ray tube. The magnetron is the type of tube used in all microwave ovens. In spite of the advancing state of the art in power semiconductor technology, the vacuum tube still has reliability and cost advantages for high-frequency RF power generation. Photomultipliers are still the most sensitive detectors of light. Many televisions, oscilloscopes and computer monitors still use cathode ray tubes, though flat panel displays are becoming more popular as prices drop.
The fluorescent displays commonly used on VCRs and automotive dashboards are actually vacuum tubes, using phosphor-coated anodes to form the display characters, and a heated filamentary cathode as an electron source. These devices are properly called "VFDs", or Vacuum Fluorescent Displays. Because the filaments are in view, they must be operated at temperatures where the filament does not glow visibly. It is relatively easy to create highly customized VFD display designs, with all the legends required for a specific task. These devices are often found in automotive applications, where their high brightness allows reading the display in daylight.
Some tubes, like magnetrons, traveling wave tubes, carcinotrons, and klystrons, combine magnetic and electrostatic effects. These are efficient (usually narrow-band) RF producers and still find use in radar, microwave ovens and industrial heating.
Gyrotrons or vacuum masers, used to generate high power millimetre band waves, are magnetic vacuum tubes in which a small relativistic effect, due to the high voltage, is used for bunching the electrons. Free electron lasers, used to generate high power coherent light and perhaps even X rays, are highly relativistic vacuum tubes driven by high energy particle accelerators.
Particle accelerators can be considered vacuum tubes that work backward, the electric fields driving the electrons, or other charged particles. In this respect, a cathode ray tube is a particle accelerator.
A tube in which electrons move through a vacuum (or gaseous medium) within a gas-tight envelope is generically called an electron tube.
Some condenser microphone designs use built-in vacuum tube preamplifiers.

As of 2008, scores of small companies are manufacturing audiophile amplifiers and preamps that use vacuum tubes.[4]
Vacuum tube can also mean a tube with a vacuum. It is e.g. used for demonstration of, and experiments with, free-fall.

Information from Wikipedia.

Cooling

All vacuum tubes produce heat while operating. Compared to semiconductor devices, larger tubes operate at higher power levels and hence dissipate more heat. The majority of the heat is dissipated at the anode, though some of the grids can also dissipate power. The tube's heater also contributes to the total, and is a source that semiconductors are free from. Caution should be used in handling heated tubes, as the temperature of the glass may be high enough to easily and quickly burn the skin, even with low-power miniature tubes.
In order to remove generated heat, various methods of cooling may be used. For low power dissipation devices, the heat is radiated from the anode—it often being blackened on the external surface to assist infrared radiation. Natural air circulation or convection is usually required to keep power tubes from overheating. For larger power dissipation, forced-air cooling (fans) may be required.
From the inception of this technology until the 1950s, the dominant approach to cooling low power tubes remained aimed at avoiding immediate or very short term failures. For noncritical consumer applications, and in absence of technological alternatives, tube failures did not create major problems for equipment manufacturers, as the cost of tube replacements was borne by end users long accustomed to the experience. Some tubes for the US defense market featured a metal casing, as opposed to glass, and an opaque, black finish that facilitated both heat conduction and radiative cooling. In some highly specialized professional applications where replacement was out of the question, such as undersea cable repeaters, no failures were acceptable. Moreover, as vacuum tube based defence systems became increasingly complex and deployed in ever increasing numbers, it became clear that point failures which were individually easy to diagnose and rectify had a devastating effect on the uptime of systems that contained tens, hundreds, and especially thousands of tubes. This resulted in both the creation of special long lasting tubes for projects such as Whirlwind and SAGE, and also in special tube shields that aided heat dispersal and could be retrofitted on existing equipment. These shields act by improving heat conduction from the surface of the tube to the shield itself by means of tens of copper tongues in contact with the glass tube, and have an opaque, black outside finish for improved heat radiation.
High-power tubes in older, large transmitters or power amplifiers are liquid cooled, usually with deionised water for heat transfer to an external radiator, similar to the cooling system of an internal combustion engine. Since the anode is usually the cooled element, the anode voltage appears directly on the cooling water surface, thus requiring the water to be an electrical insulator. Otherwise the high voltage can be conducted through the cooling water to the radiator system; hence the need for deionised water. Such systems usually have a built-in water-conductance monitor which will shut down the high tension supply (often tens of kilovolts) if the conductance becomes too high. Some very high-power transmitters, such as those used in shortwave broadcasting and VLF communications, use pressurized steam for cooling. Modern transmitters using tubes mainly in the PA section are now largely cooled by forced air through a radiator or other heat-sinking device.

Information from Wikipedia.

Applications

Tubes were ubiquitous in the early generations of electronic devices, such as radios, televisions, and early computers such as the Colossus which used 2000 tubes, the ENIAC which used nearly 18,000 tubes, and the IBM 700 series.
Vacuum tubes are less susceptible to the electromagnetic pulse effect

of nuclear explosions. This property kept them in use for certain military applications long after transistors had replaced them elsewhere. Vacuum tubes are still used for very high-powered applications such as microwave ovens, industrial radio-frequency heating, and power amplification for broadcasting. Many audiophiles, professional audio engineers, and musicians prefer the characteristics of audio equipment based on vacuum tubes over electronics based on transistors. Because this tube sound is so sought after there are many companies which still make specialized audio hardware featuring tube technology. Tubes are still being manufactured today in China (Shuguang), Russia (Reflector Corp. and Svetlana Electron Devices), USA (Westrex Inc.) and Slovakia (JJ-Electronic).

The characteristic s

ound produced by a tube based amplifier with the tubes overloaded (overdriven) is widely used in electric guitar amplification, and has defined the texture of some genres of music, such as classic rock and blues. Guitarists often prefer tube amplifiers for the perceived warmth of their tone and the natural compression effect they can apply to an input signal.
In 2002, computer motherboard maker AOpen brought back the vacuum tube for modern computer use by releasing the AX4GE Tube-G motherboard. This motherboard uses a Sovtek 6922 vacuum tube as part of AOpen’s TubeSound Technology. AOpen claims that the vacuum tube brings superior sound.

Information from Wikipedia.

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