Questions about tubes

Go to SonicFrontiers.com and find the articles they have posted. One is called "a taste of tubes" These are awesome reading for a beginner.

Mwilson I've had 3 experiences with KT88's and found your comment contrary to my experience.
1) bought a quad of EH Kt88's for my Jadis Orch Refer(KT90 amp).
2) heard 2 different Audio research with Kt88's
3) home demoed a Chinese KT88 amp
From these limited experiences I found much less bass and treble extension vs the KT90's. Basically i found the tube to be a "warm midrange", IOW not dynamic.
I need to listen to other KT88 amp before I can make a claer judgement, as each KT88 amp will vary in dynamics. But I'm not expecting much of a change.
Just based on the shapes of the 2 tubes, the KT88 is "bubbled" and I assume for that reason offers less compression vs the narrower KT90.
The fq's get sloshed around" moreso in the 88. The 90 seems to 'spit" the fq's out, thus offering more dynamics with a 'kick".
I'm sure many here will disagree, but its just my limited experience, I could be wrong.

Dmar, i just posted a note in the TECH Talk discussion. I'll post a few ideas there and others can chime in.
Do some digging in the archive here, many fine discussions on tubes characterists.

Bartokfan, you've misinterpreted the final part of my posting. I wasn't comparing the KT88 to the KT90, but the KT88 to the EL34.

sometimes circuit designs are relatively insensitive to changes in tubes.

i have had many experiences with cd players and preamps where changing the tubes has virtually no affect upon the performance of a component.