Questions about tubes

The only dumb questions are the ones unasked - get them answered and get on with the fun! I'll start with "Tube Rolling" - this refers to the act of swapping different tubes of the same type or compatible types for different sounds. Different brands, vintages, construction styles of tubes sound different from one another and can be used to effect changes in the sound of the component. That is to say, a KT88 from one brand will sound different to varying degrees from a KT88 from another brand, and even from a KT88 from the same brand made at a different time. Some tube types are compatible with one another in certain components - for example, many amps can interchange the EL34, 6550, KT88, KT90 (and less common KT66, KT77) tubes in the same sockets. Each of these tube types has a different "family sound" from one another. The EL34 for example is known for lush midrange, but less bass control. The KT88 has good bass control and good HF extension, but less midrange magic. Tube rolling allows you to experiment with different flavors of sound, and to ultimately dial in your favorites.

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.