EL 34 vs. KT 88 ---- What's the difference?

Can someone please tell me or be able to describe the sonic differences in the use of each of these tubes?

Is one tube better than the other...or does one tube provide more warmth and tube-like qualities than the other?

Does anyone know why a tube amp designer would select one over the other?

First, the power outputs of the 2 vary significantly. In pentode/ultralinear/beam-tetrode mode, for which both were designed, a pair of '88s is capable of as much as 100 Watts, altho perhaps 70 is more common, while the '34's typical max. per pair is around 50*, with around 40 being more common.

On sound quality, the consensus seems to be that the '34 has more lushness or richness in the midrange than almost any other mid- to hi-power output tube while being a little soft at the frequency extremes. The '88 (and its very close cousin the 6550) is more balanced across the frequency band, exhibiting more-extended and -controlled bass and better-quality treble than the '34 while lacking the '34's (euphonic?) midrange richness. These differences probably can be swamped by the extremes of different brands of the 2; the above is average or typical.

* Conrad-johnson is currently getting 60 Watts per pair of '34s in their MV60, but that has much-larger-than-average (for '34s) output transformers.
hello, good question here sounds simple, but i don't think it is. I think it really depends on the speaker. I think most people would say the EL34 gives you more of the tube thing, while kt88 or 6550s give more control and better bass. Back to the speaker interface...for example, I have Khorns and they just LOVE a good EL34 amp. To wit I have tried a fair amount of VTL amps on them...the IT85, MB125,ST85 all three sound great, tried their upper end amps, the ST150, MB Sig 185 and even the MB250 all more money......preferred the the smaller amps with the EL34s.

Now try them all on a very good dynamic speaker, you might get very different results...I also have a Mac 275 Mk4...great amp uses 6550s,sounds very nice on the Khorns, but just shines on my B&Ws...again a dynamic speaker.

So thats what I have found, amp/speaker interface is key...but so is the rest of the system...to avoid going nuts with this hobby, I have a saying....if it sounds good ....buy it.
My two-cents worth. I agree with previous comments. Personally, I appreciate the 34s more. Having once owned a Sonic Frontiers SF80 amp outfitted with 88s, I was amazed at the "robustness" of the sound. This being said, once I substituted 34s, I simply liked the sound more. More like music to me.

Of course, one can always, if prospective amp allows, switch out the two tube types--kinda gives one two amps.

BTW, I still own a CJ MV45a amp--with EL34 tubes! However, my "super" system consists of Atma-sphere MA1s.
Hoosier 1, My 2 cents on your two cents.....I've used every thing in sight on my SFS80, KT90's, 88's, 6550. EL 34's and E34L's. I'm presently using SED 6550's and EI 6922's. Much smoother than 90's and 88's and a bit more life than EL34's. I give a lot of credit for the balance to the EI6922's as well as the SED's. FWIW
Hi -

Beyond the forums here and at AA you can find a wealth of information at Vacuum Tube Valley. According to one of their incredibly well researched tube profiles, the KT88 was a descendant of the 6550 which in itself was designed to meet the need for a low cost, high power tube. Both were introduced in the mid-50s, with the KT88 capable of taking more voltage. The even lower cost, lower power EL-34 was introduced by Philips in 1954 - one year before the 6550s and three years before the 88s.

According to VTV "because they (34s) were low in cost, they had a lot less "hard" vacuum and a less rigid structure than 6550s... most 34s have a softer distortion tone (in guitar applications) than 6550s because of construction differences".

I have a heavily modded Cary SLA70 which runs EL34s, 6550s or KT88s in triode or ultralinear. I got it used here on the 'Gon and it came with quads of both Svet and Sovtek 34s. I then got a set of older Teslas which offered a considerable improvement.

Happiness set in the day a quad of used Tungsol 6550s showed up. I have never even wanted to listen to 34s again. The 6550s have more slam, a lot more air and expanded my soundstage towards "you are there" dimensions. Color me happy - but some of this could be about comparing best of breed with middle of the road manufacturing.

FWIW The designers who want max watts use KT88s

One thing about the KT88 which has not been mentioned is it's affinity with transients without having to add feedback. Although I love the Manley Stingray, it is less pure (bad "opinion-type" term) than my Cary Rocket. I find the Rocket almost sounds like a single ended amp - something many people have noted. The purity is because feedback has not been added to the design - the Manley has some feedback in it. The Manley's still a great rock n' roll amp - especially if you like that Sun Studios sound, which I for one, can't get enough of. I conjecture however that plate size (bigger on the KT88 than the EL34 - more electrons, more information, this is why 845's and such sound so great despite their attrocious power curves - of course, they are also very simple circuits - see the 2A3 discussions for more - interesting though) effects transient response. Also the overall power curve is flatter with KT88's than EL34's - again the "euphony", or nice sound, depending on your take between the two. However, on something like the Stingray which uses the 34's and has the same power ration 20w triode/40w UL the transients are highlighted and the mids to me are slightly euphonic (another "opinion-type" term because of the feedback). For me the wider or more accurate beefier bandwidth of the Rocket is more relaxed and less forced, but by this I don't mean Cary-mushy which I'm sure someone will jump on me about. Actually I mean open and easy with the full spectrum. I think the EL34 can be more fun to listen to, though it's less honest. Depends on your needs. I listen to more rock n' roll and watch a lot of movies, so I need something that can get behind the music and push in a way I don't find too tubey, though I like the air, extension and decay of tubes. I happen to be familiar with these two peices, so there you go if you are designing a listening session to buy, you have some things to look for, so maybe I have helped.
I think Biomimetic makes a most excellent point regarding the comparison in saying, "the overall power curve is flatter with KT88's than EL34's." However, perhaps I am wrong, but I thought the Manley Stingray ran the EL84 tube, which is a whole 'nother kettle of fish, yet not my cup of tea...

The comment I want to discuss is the EL34 midrange, which I believe is where the tube shines, as many have commented. I want to make the distinction that the term "rich" should not be taken as warm, euphonic, etc. Rather, in my experience, it is the openess and truth of tonality that sets the midrange of the EL34 apart from anything else, tube or solid state. The most concise way I can put it is that when used in a sympathetic system, it sounds simply "right". The EL34's midrange can, in the best of circumstances, make me thing that nothing else sounds as real. It's sounds like music. In one amp I owned it was flat out breathtaking - NEVER heard notes come across so perfectly.

The converse is that in the wrong application or system the tube can really come across as bright and harsh.

The 6550 and KT88 bass certainly takes at least two steps forward from an EL34. The KT88 can produce an intoxicating mid - upper bass warmth/fatness that I tend to run towards. Those who prefer the RCA 6SN7, as I do, will more or less know where I am going with this. The 6550 doesn't really do that, it more level headed in this region. It's right here that I have a hard time NOT running the KT88 in my amps. Perhaps, it's my favorite place in the musical spectrum?

The 6550 and KT88 tubes often will sound more extended in the highs, though I will make the case that sometimes, the treble that the EL34 does produce can be superior in its clarity.

As also stated, power is significantly less, but how your system manifests this may or may not be directly proportional. On one amp that I ran, the step up in volume I needed to make was only a click or two. On another, it was the difference between being able to run in triode (the 6550/KT88/KT90) versus HAVING to run in pentode (the EL34).

The 6550 sounds the most even handed to me, yet also the most boring in many applications. The KT90 sounds kind of cold and uninspiring in the mids, though it is a most robust tube if one is looking for long life. Many folks feel the 6CA7 is superior to all, combining a fair amount of the bass richness/fatness of the bigger tubes, with a better midrange than they can produce. I am aiming to audition the Ei 6CA7 this fall in my Jadis. Which do I prefer at this point? Well, call me one afraid to take a definitive side here, but I keep going back in my amps between the JJ KT88 and Blue Glass E34L.
There is a very clear difference in the way these tubes sound. I have no idea whatsoever what the differences are in terms of construction etc. The EL 34 is known as the queen of the mid-range for good reason (I don't know the king) it clearly excels in producing a certain full and yet sweet sounding midrange it rolls off the top end a bit and tends to loose control of the bass but both end of the spectrum are reasonably pleasant. The KT-88 produces a more robust powerful sound especially at the extremes of the frequency spectrum. The mid range is there but it tends to be clinical sounding and less musical. The KT-88 is simply a bigger sounding tube and it will rock you, its just not going to be as polite sounding as the EL-34. I really like it for some types of music and it won't struggle producing tighter bass and sparkling treble. I hope that helps.
I found this thread to be very helpful... thanks to all. I currently use a Jolida 302A with B&W DM602 speakers, Audioquest Slate bi-wired cables. I find that the EL34s in the Jolida are sweet for jazz, classical, and voice but lacking a bit in precision for rock, which I still listen to very frequently. I'm just starting the process of tube rolling, so all help is appreciated for this novice.

From what I've read, if the KT-88s are compatible with my amp, I might try those for rock music. Yes? Dangers?
You are thinking of rolling KT-88s and EL34s? Perhaps I am missing something but I did not know this could be done at random.

I will say that Svetlana KT-88s in my McIntosh 2102 amp has made this amp sound as good as any in its price range and better than many more expensive amps.
Yes - I agree with the statement KT88's are less polite. I listen to a lot of rock. The point I was making is about the Manley being based on EL34 - however, it is a good rocking out amp. I was just saying that it is a more polite tube by construction, though it can certainly find it's way through any kind of job depending on how the amp is engineered overall. My understanding is the KT88 just has a bigger plate and uses power more efficiently so it has a flatter response. But look at triode sounding great - efficiency isn't everything. Plus, what kind of tube, what kind of capacitor, plus point to point wiring versus boards, plus linearity of layout... there are a host of factors other than just tubes. Everyone is so gung ho about the KT88 here - I am too, I use them, but I thought it might be good to illustrate the other side by finding an amp that wasn't quite so warm and fuzzy with the EL34, while still being hyper ... "musical" for lack of a better term.
Mjpflieger, the Jolida 302A/B is set up for the EL34 only. It cannot use the larger 6550/KT88/KT90 tubes in stock form. Conversely, the Jolida 502 cannot run the EL34/6CA7 as things are.

However, modification can be done to either so that they can run the other set of tube, or run all of the spectrum.

And, for what it's worth, to my ears, the Jolida 302A/B is sonically far and away the winner over the 502.
I have owned and/or heard a number of EL34 and Kt88 amps. I generally agree with the comments that the KT88 is more balanced and extended and the EL34 is "fuller" in the mids. However, as they say, execution is everything. The Vac Avatar that I recently sold used EL34s. In UL, it was close to the sound of the VAC KT88 amps. In triode, with the right speakers (moderate impedence & eff. of 88-92 db.) the midrange could be sublime; not overly rich or warm, simply right, exceeded only by a few of the very best tube amps. Still good extension on both ends, maybe very slight roll-off on treble with deep bass but of course not as much slam as SS. A couple months ago I had the opp. to hear VAC's new top of the line $19,000 integrated, which I believe uses KT88s instead of the 300Bs that most of VAC's more expensive amps have used in the past. Its sound was similar in character to the Avatar in triode, except better in every regard. Perhaps the best amp I have heard. Intimate yet dynamic and detailed.

Another plus for EL34, I think, is the Mullard reproductions that can go with them - not overpriced and sound great.
After reading this post I am curious to try some rolling myself, just to hear the differences in my set up. Does anyone know if the Sonic Frontiers Power 2 supports using the EL-34 without modifications?
This has been a great thread all. Thanks for all of the information.
Yeah 84, not 34 ...duh on my part...
Wow, it takes a person of real character to return to make a correction to an earlier statement. You have won a lot of admiration from me, Biominitic!
The New Sensor Mullard EL34 or JJ Tesla EL34L are both current, affordable and sound great with the 302B. I prefer the Mullard over the JJ, but not by much.
Also the Tung-Sol 12AX7s are in my opinion, the best of the affordable 12AX7s for all Jolida equipment. I am also running their CDP, Phono pre and Tuner with these tubes.
Any further thoughts?
Why can some amps use EL34 or KT88 while other amps cannot use them interchangeably?

Does the output transformer have to "match" the tubes? If yes, what are the impedance differences?
Some amps can use both el34s and 88s b/c they have variable bias, allowing you to adjust the bias to the appropriate level for different tubes.
Stewie, I think it is not that simple. Different plate voltage and the bias range of the fixed bias circuit both come in to play I think. Just having the ability to adjust bias is not enuf. A user should always ask the manufacturer if use is possible, or at a minimum a knowledgable techie (which I am not) who knows the amp before trying different tube types.
Is there anyone who has an amp that is made to handle both EL34 and KT88 and prefers the EL34 generally, that is if you had to make a choice you would stick with EL34 over using the KT88. I think one of my amps (Music Reference RM9 SE) was built around the Siemens EL34 tube, but I still think it sounds better with the Genelex KT88 reissues.
Pubul57--My Dynaco mk iiis take both el34s and kt88s, but they're powering only the midrange/tweeter cabinets of my VR4 HSEs. Also, my kt88s are EH and the 34s are the winged c variety. That said, despite the fact that the fat bottle kt88s are the most pleasing to look at (not that anyone cares about that!), I find myself going back to the el34s. The difference, to my ears, is slight, and I doubt most could hear the difference if they weren't trying to hear it. But there is something special about the el34 midrange, at least in my system--not just more of it, but a different sonic character. Liquid is a word often used, and that gets at it.
PrimaLuna amps will accept EL34 or KT88. I tried both driving my Klipsch RF7's and agree with Jeffreybehr on the sound difference between the two.
My Granite monoblocks took both the KT88 and EL34. I could never get them to sound right with the EL34, and am pretty sure it was an issue of bias, though I didn't pursue it too much.

My Jadis DA30 and DA60 integrateds can also use either, and I strongly prefer the EL34 in both of them, provided the right driver tubes are used to address the loss in low frequencies that occurs otherwise. In a nutshell, the EL34 really walks away from the KT88 in the midrange, giving both amps a far more musical and natural presentation.
I agree with most of the above comments, having owned and used EL34, 300B push pull, 300B SET, and heard a lot of KT88.

I love the sound of EL34 in Ultralinear mode, which gives both sweetness and "pace" or "robustness" or whatever you want to call it. With just about any dynamic speaker, that's a heavenly combination. Note that 300B tubes, which are also glorious, are far more expensive, and ergo more difficult to experiment with.

Often the KT88 has been used in stacked configurations to provide high power tube amplification. How the tradeoff between power and tube "sweetness" comes off is very subjective. Well implemented, they can both be great.

I am curious if anyone has tried to use KT88 ultralinear amps with low sensitivity exotics, such as Soundlabs? Any user experiences?
EH6CA7s are the way to go with Manley Snappers!
in my experience, it is the openess and truth of tonality
that sets the midrange of the EL34 apart from anything else,
tube or solid state. The most concise way I can put it is
that when used in a sympathetic system, it sounds simply
"right". The EL34's midrange can, in the best of
circumstances, make me think that nothing else sounds as
Agreed. Couldn't have been said better!
I had McIntosh 2301 mono's with KT88 and now I have old Manley 240REf mono's with el34 aand like them better in my setup, more spark and musicality to my ears.