EL34 / 6CA7 / KT77 Tubes
Marshall tube amps are the most well-known EL34 tube guitar amplifiers but there are many others who arrived on the scene in later years. In the tube audio world, it was companies like Dynaco, Leak, and Mullard among others who help boost the EL34 tube’s popularity.
Other common substitutes for EL34 vacuum tubes are 6CA7 and KT77 tubes. Although not identical, they are close enough to be considered direct substitutes in almost any instance. The EL34, 6CA7 and KT77 also have similar pin outs. Be sure to check out our EL34 / 6CA7 / KT77 tube reviews page for more information regarding the sound qualities of these tubes.
Many of the EL34, 6CA7 and KT77 tubes listed here also have customer tube reviews. We also indicate top sellers for the EL34 tube type.
Be sure to click the “Additional Info” tab when viewing a specific EL34 tube. There you will find related articles and downloads such as datasheets and matching information when available. Other excellent links for technical information can be found at EL34 tubes in Wikipedia, EL34 tubes in Duncan Amps, and EL34 tubes in The Tube Directory.
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The quick answer to the difference between EL34 vs 6CA7 or EL34 vs KT77 is simple.
EL34, 6CA7 and KT77 are all drop-in replacement of each other. You can use 6CA7 or KT77 in place of EL34. Electrically, they are the same.
Now, with that out of the way, there is a fair amount of difference in how these tubes sound. Yes, EL34, 6CA7 and KT77 are not the same when you hear them, and there is a reason for it.
To understand the difference, let's start with a bit of history.
Mullard EL34 - European Invention
Mullard UK designed the EL34 tube in the 1950s.
The venerable EL34 tube produces clean, smooth output. EL34 handled lots of power in a thin glass tube. The smaller size and high power made the EL34 tube very popular in audio and guitar tube amps.
Many amp manufacturers such as Marshall, Hiwatt, Orange, Leak, and Dynaco produced legendary amps with the EL34 tube.
EL34 tube has a fairly unique sound. In guitar amps, EL34 is all about mids and upper-mids. You get more of that brown tone with your rhythm work. EL34 gives you smooth note separation with complex harmonics and sparkle.
In audio amps, the smooth velvet mids of EL34 takes the center stage. If you like listening to classical or jazz music with horns and vocals, the EL34 tube is the perfect fit.
Today, there are many current production EL34 tubes, such as Mullard EL34 and TungSol EL34B.
These EL34 tubes follow the original design, but with modern manufacturing and quality control. They provide the classic rich mid-tones of the EL34 with consistency and reliability.
If you are looking to replace EL34 tubes, Mullard EL34 and TungSol EL34B are the go-to tubes. They are step up from the OEM tubes shipped with the amp, and will provide great tone.
Sylvania 6CA7 - America's Answer
Not to be outdone, Sylvania introduced the 6CA7 tube in the US shortly after the EL34 tube came out.
6CA7 was not a copy of EL34. The Americans adopted the same beam-forming tetrode design as the 6L6 to create 6CA7.
In a beam tetrode, a wing-shaped plate forms a beam of electron. Because of the beam-forming wings, the plate assembly is physically larger. 6CA7 comes in a fatter bottle because of this.
The 6CA7 and EL34 tubes sound distinctively different. On a sonic scale, the 6CA7 tube is a hybrid between EL34 and 6L6 tube. Like the 6L6 and 6550, 6CA7 tube has a more pronounced low end.
In a guitar amp, this makes for a tone that is more substantial. People often describe 6CA7 sound as heavier and darker than the EL34 tube.
Current production Electro-Harmonix 6CA7EH is an excellent reproduction of the original Sylvania 6CA7. Electro-Harmonix 6CA7EH does the 6CA7 tone very well. 6CA7EH is worth considering if you are looking to get a bit more bite and roar from your EL34 guitar amp.
GEC KT77 - Ultimate EL34
GEC in West London, England, introduced the KT77 tube in the late 1950s as the ultimate medium power audio tube.
KT77 tube employed an internal construction resembling 6CA7, but GEC optimized the KT77 tube for high-fidelity audio applications. The KT77 was the ultimate EL34 for audiophile use.
Unfortunately, since the original KT77 was manufactured only by GEC, KT77 was rather rare, especially in the US.
Current production Genalex Gold Lion KT77 was introduced in recent years to recreate the original magic. Gold Lion KT77 has a smooth texture and balance, and is worthy of consideration as a premium upgrade for any EL34 amp.
Then they were the same...
As years passed and transistors took over, there was less demand for tubes.
By the 1980's, tube manufacturers consolidated worldwide, and the distributors started treating EL34 and 6CA7 as the same tube. Many EL34 tubes from this era were marked as 6CA7, and vice versa.
In fact, some tube brands got lazy and labeled everything EL34/6CA7.
KT77 all but disappeared when GEC quietly stopped production in the 1980s, as people danced funny to synth music wearing shoulder pads and dangling earrings.
Back to the Roots
In recent years, the tube manufacturers returned to the roots of these great tubes.
To cater to increasingly demanding tastes of tube amp aficionados today, tube manufacturers are releasing tubes that are true to the original design.
Current production EL34 tubes closely resemble Mullard pentode design. Likewise, current production 6CA7 are beam-forming tetrode like the original Sylvania design. And re-issued KT77 deliver the legendary magical sonics of the original.
There is now a wide range of tonal landscape to choose what fits you best. Please visit our EL34, 6CA7, KT77 tubes page to select the right tubes for your amp!
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EL34 / 6CA7 / KT77 Tube Reviews
Are you looking for the very best tubes for your vacuum tube amplifier?
This is the place to start. Check out the following tube reviews for guidance in getting the best possible tone out of your tube gear.
(View our complete selection of EL34 / 6CA7 / KT77 vacuum tubes)
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.
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.
1970 Marshall Bluesbreaker 2x12 combo
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.
Click to view our EL34 Tube Comparison Chart
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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Gold Lion KT77 - This tube was a treat to listen to. Since many of us have never actually listened to a KT77 from the original producer, I can not say that they nailed the reproduction. You really have to think of this tube as its own entity. Here is what I can tell you about it. The Gold Lion KT77 is a drop in replacement for an EL34 or 6CA7. The sound however is not typical of an EL34 or 6CA7. It is more of a hybrid. The tube delivers all the mid punch you would expect in an EL34 but also has a top end that is more open and bright. It’s definitely got a bit of a 6L6 designed into it. I tested it in a Marshall 2205 50w head and was able to get that '70’s rock sound but with some bias adjustment could also dial in a VOX-like chime. This really has to be looked at as a new choice in power tubes. If you have a Marshall and never could decide if 6550 or EL34 was the way to go, you now have a third option.
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JJ 6CA7 - Prior to this tube being introduced the choice in a 6CA7 tube was NOS or the Electro Harmonics 6CA7EH. JJ has provided another choice and another price point. JJ tubes tend to be well made and this model fits well into the family. Nice construction, good glass, and the base and pins are well assembled. Although this is a replacement for the EL34 tube, the 6CA7 tube looks nothing like a pentode. In fact, an examination reveals what look like the beam forming plates you usually see on a 6L6 power tetrode. I’m not 100% sure of what’s going on in there. The JJ 6CA7 tube looks and sounds like a 6L6 but biases like an EL34. When installed in a 50W Hiwatt head these tubes just roar. It’s a classic sound for beefy rock anthems. The sound is firm and articulate. A number of customers have reported that this 6CA7 tube is darker sounding. Your mileage may vary but I found nothing dark about them at all. Smooth yes, dark, not so much in my testing.
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JJ E34L (EL34) - Are you a fan of rock and roll music? If you answered yes and use EL34 tubes then this could be, your go-to bargain.
JJ makes great tubes at affordable prices and the E34L is no exception. It is built in a very rugged package with thick glass and a welded plate assembly. Two mica spacers that feature a high number of support points at the top and bottom of the plate support the assembly.
Do not let the price of these tubes make you think they are anything but excellent. There is a tendency in the tube world to shy away from things that are reasonably priced. However, I would counter that today we need as many bargains as we can find, and this tube qualifies.
The sound of the E34L is very much a rock sound. The bass is bold and the midrange is thick. High-end response is very good but not as bright as some of the Chinese models on the market today. The compression characteristics on the E34L do not really become noticeable until you push the tube into overdrive. This allows for a little more sparkle at lower volumes and an audible thickening of the sound as the volume goes up.
This is a good tube at a great price. If you want more high-end sparkle then the JJ EL34-II might be a better choice for a few more dollars. If you want to rock then the JJ E34L should meet all your needs.
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JJ EL34-II - JJ has upped their game with the new EL34 II, and the design change is truly big enough to warrant the use of the new name. Many companies put an existing tube into a new bottle, but JJ has done the opposite.
The familiar tall, dome topped bottle is still there but everything else has changed for the better. The new tube has a traditional EL34 plate structure but they have replaced the plate assembly with a slightly smaller unit that features crimped plates instead of spot welded plates. The crimping is clean and precise making a very solid and quiet assembly. The mica spacers are well formed and very secure. This looks more like something from Siemens than JJ.
Listening to this tube was a bit of a surprize because I usually find EL34 tubes to be a bit soft sounding, and this tube is different. There seems to be a bit more life in this tube as compared to the previous model. I found there to be a really nice top end that is smooth and free from harshness, while still delivering a nice bit of sparkle. At the other end of the spectrum I found the bass to be very firm and clear with no boominess. For guitar use the midrange is where the action is and this tube handles it nicely. I didn’t hear any honking Mids. It seems the design goal was to make something with broad frequency response that extends a little further than the standard JJ EL34. The closest sounding match would be the Tung Sol EL34B.
This new tube has really earned the right to be labelled version II.
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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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Mullard EL34 - One of the most famous brands in the history of vacuum tubes now belongs to a different entity. Not unlike Tung-Sol and Gold Lion, this is a new-ish tube with an old name. Fortunately, the new tube has a lot in common with the originals.
There seems to have been efforts made to make current production resemble the originals. The classic tall bottle with a flat top, featuring two large cooling wings attached to the support rods just below the getter assembly. It is a classic look for your audio equipment.
The sound of these tubes is pure EL34. Smooth and balanced overall, the frequency response is a bit softer in the midrange than some other models. Mullard EL34 tubes have a smooth, liquid feeling that is very different from a 6L6GC. Some people used to refer to this as the sound of a soft vacuum. I don’t know if the vacuum is any different, but the tube has no rough edges to speak of and has that slightly compressed sound at lower levels. When you push the Mullard, the compression becomes more noticeable and helps to build a very fluid sustain.
I really enjoy these in my old Dynaco Stereo 70 for their warmth. If you want something with bite for your guitar amp these would not be my first choice. Tung-Sol EL34B’s would probably be better. If you want to smooth your overall sound and tame harsh midrange response then these may be just what you are looking for.
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Preferred Series EL34 - In a market that has a lot of options for an EL34, this tube could be a stand out. The tube design is classic EL34, with the tall grey plate you would expect. The bottle is a bit wider than some EL34 tubes and is big enough for a 6L6. The glass is nice and thick. The mica’s in the Preferred Series EL34 are nice and thick and look to have a very snug fit. This should help eliminate microphonics and the tube I tested had none, so it must be working. The plate assembly is topped with a single, small, halo getter and two oversize cooling fins mounted to the support rods. Of course the base of the tube is the signature blue of the Preferred Series octal tubes.
The sound in my single ended test amp was great. I usually run a KT66 or 6550 in this amp but this little EL34 will be there for a while. The bottom end is amazing and the tube has tons of gain before it gets dirty. The real strength of this tube is the bass and midrange. Bass notes are rock solid and the mids are very rich and complex. The high end is very good but not bright. This tube really wants to be in your JCM 800 or other amp that can generate piercing top end. Marshall users could combine these output tubes with their beloved high-gain Chinese pre-amp tubes for some real punch. Palm muting chords with p-90’s or humbucking pickups produces some seriously percussive sound. The Preferred Series EL34 can keep up with anything on the market. The extended warranty of the Preferred Series combined with the tone and build quality make this an outstanding tube for home audio and musical instrument amplifiers.
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NOS Siemens / RFT EL34 - Back when we started doing reviews of EL34 tubes, an old and somewhat tired set of Siemens EL34 was used as the reference standard. To have them available again for what I consider to be a reasonable price is great. These are the real deal. I tested three pair of the NOS tubes with different “perfect pair” matching numbers just to see if there was consistency and I’m happy to report that when biased the same they were very consistent. When I think of German power tubes I think of a big warm sound that doesn’t cause listening fatigue after an hour of playing. Many will say that Telefunken is king but the Siemens brand was always under rated. I ran three different types of EL34 tubes through the Marshall in one night of testing and the Siemens was the only one that required me to reduce the bass response. These tubes are extremely warm sounding and if you have one of those amps that sounds thin at lower volume levels, these should take care of that problem in short order. Midrange response seemed slightly skewed toward the bass side. This is no doubt where the extra warmth is coming from. The high end was smooth and clear without a trace of harshness. Construction is very good with the straight, flat-top bottle that is characteristic of the Siemens EL34 tube. No issues at all with noise and this is likely because of the thick laminated plate structure. You can see how heavy these plated are by examining the four large crimps down each side of the plate. This is a great opportunity to own NOS EL34 tubes without breaking the bank. And based on Siemens track record they should last longer than anything being made today. Home audio, guitar amps and those big old Grundig and Normandy console stereo units will all benefit. Enjoy.
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Shuguang EL34-B - For many years no one would have believed that Chinese tube factories could turn out work 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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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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Svetlana EL34 - The Svetlana is the perfect tube for classic rock. The midrange is very pronounced and 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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Tungsol EL34B - The Tungsol EL34B is likely to become the #1 choice of currently produced EL34 tubes. The build construction is great all around and the move to welded plates will likely keep “EL34 rattle” to a minimum over time. The manufacturer claims that this tube has a hint of 6L6 in its tone thanks to manipulating the plate impedance. This is absolutely true, but the effect is most notable when playing clean and to a lesser extent when the tube is driven hard. At lower volume settings you hear a very pure balanced tone with a bit of the 6L6 sparkle in the higher frequencies while providing a midrange that is a little less prominent than most EL34 tubes. The tubes were very open and airy. The bottom end was percussive in the 2x12 open back combo. When driven into distortion it starts off a bit crunchy like a 6L6 but as you push it, the sound blooms into that singing EL34 tone with great sustain and modest compression. I love these tubes. Over the years I’ve tested many tubes but this is the first time I’ve had to tell myself to stop playing and get on to the next set!
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Winged "C" / SED EL34 - If you want one EL34 tube that will do anything the Winged "C"/SED EL34 tube 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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EL34 equivalent tube types
The Genalex Gold Lion reproduction KT-77 is in my opinion, and many others, the best EL34 variant currently available. They are night and day better than anything else I have tried.
Ok - that is what I will try, the Gold Lions. Thanks everyone!
jond speaks the truth. I’m loving the KT77’s based on his say-so.
I had bad luck with JJKT77s in that they don't cut the sonic mustard compared to the KT88s (either surprisingly great sounding no longer available Sovteks or newer Gold Lions) currently in my SEP "Fire Bottle" HO. I might try the GL 77s, but...meh…the amp sounds so damn good I kind of lost interest in 77s…go HO!
I have a Dynamo 34SE MKII which has more grunt than the original.Have used Black Treasures,Siemens and Gold Lion KT77s'.All good but my favorite is the KT 77's.
@wolf_garcia "I had bad luck with JJKT77s in that they don't cut the sonic mustard."
You're right about that. Not sure why, but JJ did a poor job with this tube. Kind of a head scratcher, as their E34L (as Viridian / Marty pointed out) and EL34 sound very good.
I also think the Shuguang EL34B will surprise a lot of people, and sound fairly close to the JJ EL34. And though I'm generally not a fan of most Russian tubes, for a bigger and robust yet easy to listen to sound overall, the ElectroHarmonix Big Bottle 6CA7 make me happy
Would a 7581a work? Tung Sol have a new tube out that is real nice. Super bass and crystal highs. I replaced a quad of 6L6GC with them.
+1 for GL KT77. Smooth and non fatiguing
I also like the GL kt77 the best in new production lines of new tubes. Smooth and clean with good details. It just lacks little punch in lower region, so voice is not as rich as NOS tubes.
I just retubed with the Mullard EL34 repops and 12ax7s and they really sound great in my Quicksilver Mid Mono amps....
Equivalent el34 tube
By Ed Malaker
The EL34 and the 6CA7 are two power tubes that can cause a lot of confusion when purchasing replacements, because they’re very similar and are actually replacements for one another. They do, however have different internal designs, and they’ve changed slightly over the years.
The EL34 tube came first, and it was designed in the 1950s by a European company called Mullard. Two EL34 vacuum tubes are capable of producing 90 watts of power under ideal circumstances. As a result, high-gain output made them very popular for use in guitar amplifiers, and they remain so today. See the EL34 in Fig 1.
EL34s are said to have a “British Sound,” and this can be heard by listening to British amps such as Marshall, Hiwatt, Orange, Vox, etc. You can also try listening to well-known players such as Jimi Hendrix, Eddie Van Halen, and Jeff Beck.
Once the EL34 became popular in England, the American company Sylvania quickly released the 6CA7 vacuum tube. The 6CA7 is meant to be a replacement for the EL34, but it is an original design that imparts its influence on the resulting tone of the amplifier and is similar in sound to the 6L6 vacuum tube. See the 6L6 in Fig 2.
Amplifiers that use the 6CA7 tube are said to have an “American Sound.” This can be heard by listening to American amps such as Fender, or players such as Eric Clapton, David Gilmour, and Jack White, who use these amps.
With the introduction of the transistor, the popularity of tubes began to wane, and many companies decided to combine the EL34 and the 6CA7 into a single design. From that point on, it has been possible to purchase an EL34/6CA7 tube.
Despite its years of success, the transistor has not been able to compete with the sound of tubes. So, vacuum tubes have remained in demand and many companies have gone back to building the original EL34 and 6CA7 vacuum tube designs.
You can choose a vintage or modern EL34, vintage or modern 6CA7, or EL34/6CA7 to replace any of those tubes in your amps and they will work fine. There are also other designs, such as the KT77 vacuum tube, that are “drop-in” replacements. These other tubes are usually modified versions of the EL34 or the 6CA7.
So, knowing that these tubes can replace each other without harming your amplifier, you’ll find a world of new tonal possibilities to explore. It will also help you keep your amp running if you can’t find the specific tube your amp requires.
How Long Do EL34 Tubes Last?
An EL34 vacuum tube is a power tube which generally deals with a lot of power and current. Handling this high current will cause it to wear out much faster than the lower powered preamp tubes, but you still get quite a bit of life from a power tube. The EL34, along with other power tubes such as the 6CA7, 6L6, and 6V6, are generally expected to last around 1,000 hours of regular use. Of course, sometimes vacuum tubes will go bad prematurely, and they are relatively fragile.
Do Power Tubes Need to Be Matched?
Yes, you will need to match your tubes. This is also known as setting the bias, which refers to setting the amount of current that runs through their base plates when the amplifier is idling. Too much current will shorten its lifespan while too little will cause unwanted distortion. Bias setting is necessary because of the design of the tubes and the fact that each is slightly different.
Do I Have to Bias Preamp Tubes?
No, you do not have to bias preamp tubes. They handle much less current than power tubes, so the minor differences between each vacuum tube is much less pronounced. Set by using a hardwired resistor, preamp tubes are “self-biasing,” or cathode-biased and do not need to be adjusted.
What is the Difference Between EL34 and EL84?
The EL84 vacuum tube is a modified version of the EL34 vacuum tube. It has been specifically designed to beak up quicker at lower volumes and produce more distortion. The EL84 vacuum tube often powers smaller practice amps and effect pedals, and it is notably popular among metal players. The downside of this tube is that it runs very hot. Because of this, its life expectancy is barely half that of standard power tubes, and it lasts only about 500 hrs.
Updated July 24, 2020.