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

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

best,
ck

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?