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

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.
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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

best,
ck