Guitarreando en casa: EL84

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11 de octubre de 2008

El tubo o válvula EL84

EL84
From Wikipedia, the free encyclopedia

Common variants of the EL84, manufactured today in Russia, Slovakia and Yugoslavia.

The EL84 (European designation - known as the 6BQ5 in North America) is a vacuum tub (a.k.a. valve) of the power pentod 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 Britis 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- Čadca (JJ Electronics), and Serbia- Niš (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.

http://en.wikipedia.org/wiki/EL84

28 de septiembre de 2008

dealers de tubos en santiago

aquí pueden revisar precios ... en dealers en Santiago ...
yo le he comprado a Mex, super buena onda; yo me equivoque de modelo, y el amablemente no tuvo ningún inconveniente en cambiármelo.

http://www.mex.cl/power.htm

http://www.importedgoods.cl/ehxtubos.html

Rz

EL84 Tube Type Review

The Complete Reviews

Electro Harmonix EL84-EH - 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.

EL84 (also 6BQ5) - Power Vacuum Tube

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.

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.

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.

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.

http://thetubestore.com/el84review.html

Rz