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.

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.

Whether you end up being happy with tubes may depend on how carefully you select a tube amp/integrated to match your speakers and which produce a tone you find attractive.

I'm not familar with your speakers so I won't make any recommendations on amp types, but for example (remember MWilsons comments on the generic sound of tube types), if your speakers/system are more on the cool side of neutral and do not have really deep bass and you want to warm it up an amp based on EL34's could work quite well, an amp with KT 88's might as well, but you probably would not like either KT90's which can be bright in the highs, cool in the mids but very tight in the bass, or 6550's which are not as bright, nor as tight in the bass, but more or a balanced tube that will let your components sound pass less altered.

In addition, in selecting your amp, you will want to insure that it has the ability to drive your speakers in the first place, which has all to do with minimum impedence values of the speaker, its impedence curve (which should be as smooth as possible - no big impedence spikes or dips), nominal impedence of the speaker, and output impedence of the amp itself.

Don't get wound up about tube 'rolling'. Its a hobby within a hobby. Ultimately though it can be one of the most fun things about tubes - if you want to change the tone of your system.

Lets say for example you buy a new CDP which initially sounds too cool in tone, your amps ability to accept a wide variety of tubes gives you a lot of flexibility in changing the tone of the CDP. You don't have to get a new CDP, just a couple of tubes.

However, I have found that most amps which accept a wide variety of tubes usually sound best with the type of tube which their design was based upon. I would not buy an amp designed around a KT88 and expect it to sound as good with an EL34 as an amp designed around an EL34.

FWIW, YMMV, however despite comments of others, don't let anyone kid you, changing tubes makes a difference. Sometimes its small, sometimes its big. But there is a difference - it just depends on whether or not the difference is in an aspect of audio that is important to you (for whatever reason).

Hope that helps a bit.........