6550 tube vs KT88

Thanks Dave, i'm trying to understand these tubes. . I'm just want to get at the bottom of things here. As you know many opinions and posts on this site can be just as biased as some sound systems I've heard.
Lets just cut to the quick.
What are the EXACT characterists of a 6550, 88, 90?
Provided we are usinga amp source of high clarity, superior purity?

I realize this can't be done, as each speaker will voice differently.

I need to order that quad of JJ 88's and then I can feel better of my opinion on the 88's.
I'll try next month, as I'm still unemployed post katrina and cash is low.

"What are the EXACT characterists of a 6550, 88, 90?"

Wrong question. I have tried a few brands of new production 6550's and KT88's in my VTL's, and each kind sounded different. As anybody with a little tube rolling experience can tell you, there is no "one sound" for each tube type -- different versions with the same model designation are not physically or electrically (and hence sonically) equivalent, and that includes different brands, factories, and vintages.

I'm also not sure that your amp, apparently designed to use KT90's, is really a good candidate for KT88's as drop-ins. For instance, I know that my amps, which come stock with 6550C's, can't use KT90's without resistor changes, although KT88's are fine. And if your amp uses autobias, there may be no way for you to tell if the replacement tube type is not being biased in the proper range by a circuit not designed for it.

FWIW, in my amps a swap from SED 6550C's to EH KT88's produced improvements in essentially all the same areas you're complaining about, and the overall effect would be outstanding for a classical listener in my view. But although my speakers are also about 87dB sensitive, my amps are ~200w, and obviously everything else is different too. BTW, when comparing tubes you must make sure one set isn't wearing out, or still breaking in -- that will totally skew the results as well.

I'm also not sure that your amp, apparently designed to use KT90's, is really a good candidate for KT88's as drop-ins.
Zaikesman (Reviews | Threads | Answers)

Zaikesman makes a cogent point that amplifiers are usually voiced with a particular tube, regardless of their ability to function with several types of tubes.

11-01-00: Rcprince
I'd suggest you ask the manufacturer of the amps directly. The new Jadis have transformers optimized for the KT90s...

Therefore, it's likely an amp sounds best with a particular tube from a specific manufacturer (in the case of Jadis, the Ei Yugo KT90), and one cannot make generalizations about the quality or suitability of other tube types based only on one's limited experience with one amplifier that has been specifically designed for a particular tube. In fact, the JOR will probably sound different with Electro Harmonix KT90 than it does with Ei Yugo KT90.

Couldn't resist huh Tvad?
:-)))))

Couldn't resist huh Tvad?
:-)))))
Audiofeil (Threads | Answers)

Perceptive posts deserve attention, and Zaikesman's post was right on point.

OK, no more questions, your honor. :)