6550 vs KT88 vs KT90

I'll throw in my two cents, since I've got amps (Jadis JA 80's, vintage about 1990) which can use a few of the types mentioned. I agree with Greysquirrel that it depends on the amp involved. My amps won't run with the KT-90's (at least Frank Garbie said it would not be a good idea), and as between the KT 88s and 6550s, I prefer the former. The best 6550's I've used (old ARC Phillips and Svetlana 6550Cs; couldn't afford the Tung Sols, and the GE's just sounded ordinary) probably control the bass a little better, but ultimately sound leaner. On a rich balanced speaker (my old Duntech Princesses, for example), this was fine, but on a more neutral speaker they could sound too thin. The KT88s I use (old MO Valves) are much richer and more harmonically correct in the midrange, with good bass and a wonderful sweetness--the classic tube sound, I suppose. I'm curious as to how the new Russian KT88's stack up against the vintage tubes. My gut feeling is that the older Jadis amps were designed around the older KT88s; in fact, I believe the newer models may have been designed, particularly the transformers, around the KT90's. I've heard the newer Jadis amps with the KT90's, and they sound terrific. So I'd suggest you take the amplifier you want to use the tubes in into account. Hope I haven't confused you even more.......

Rcprince, you may want to e-mail Jadis regarding the use of KT90 tubes in your amp. They go out of their way to recommend KT90, and to avoid KT88 with me. They say they have seen reliability problems with KT88s. I have never had this experience. Quite the contrary. And, while Frank Garbie is very helpful, his information is often at odds with what I get from Jadis directly. So, again, I would ask THEM about KT90s in your amp. They always give me a response within a day or two. Good luck!

Trelja: Thanks, I'll give that a try. On the reliability, the newer KT88s, particularly the Chinese lower grade makes, have had reliability problems. The vintage stuff is a different story. All the 6550s I've used in the JA80s have started going bad, and blowing the protective fuses, within a year to 14 months (in my ARC Classic 150s, the same Phillips tubes lasted 5 years). I've had the KT88s in there for over two years now with no problems. I must admit having a preference for the MO Valve KT88s, even over the KT90s I've heard in Jadis equipment; just a matter of preferring the darker sound, I guess. But the prices.....

Trelja,which of the Rogue products have you used.Can you comment on svetlana 6550C Vs Sovtek Kt-88

Tml12, I have EXTENSIVELY used both the stereo and monoblock Rogue amplifiers. Wonderful sound, but not what I call "classic tube" sound. The new tube sound(Rogue, Jadis, Audio Research) is much more neutral, powerful, and extended(solid state sounding, at least to me). What people mean when they say the best of ss and tube amps are converging. The amps sounded more to MY liking with the KT88s. A bit more sweet. But then, I like syrupy sweet tube amps(even though my Jadis is not). I know you will say this is crazy, but I always preferred the Jolida 302B over all the other Jolida integrateds, and the Rogue power amps. But, that goes back to my sweet sounding tube preference. In reality, the Rogues offer MUCH more: power, neutrality, bass AND treble extension, etc. All of the things that "the absolute sound" is supposed to sound like. Just trying to be honest in regards to my bias.