KT90 experience?

Jfacker, the KT90s sound just like the two things you heard. More power, bass, neutrality, and "solid stateness" as compared with the KT88 tubes.

Bartokfan, one thing to keep in mind is that comparisons should be made using equal numbers of tubes. If that is the case, the KT90s will do all of those things. But, since you are moving from a JOR to a DA60, you are doubling tube count, and really upping the size and quality of the transformers and capacitors. You will also now have an active preamplifier section. The DA60 bass will be superior without question. If you switched to 8 KT90s in the DA60, the comparison will once again hold true. For the record, while I have both tubes, I prefer the KT88 - it's a beautiful sounding tube.

I have used EI KT-90 Type III tubes many times as well as Svetlana & Sovtek KT-88's and both of their 6550's...

The Ei KT-90 type iii (make sure to get the type 3 - the earlier versions were more 'zippy') will produce more power than a KT-88. The bass will be better controlled and overall it will be a more linear tube. In my situation with a few different amps, it took my KT-90s about 400 hours of play time before they had the "effortless" presentation to them... they sound decent at first, but there is a bit of "strain" or congestion until they do burn in a bit. I can not explain why this seems to be. It was advised I log the hours on the new tubes years ago upon insertion and that is what I found, as well as two times since then. I don't personally find the KT-90 to be "solid state" at all after the 400 or so hours of break in. The midrange is liquid and harmonics and timbre are natural.

I do love the midrange presentation I have heard with NOS Genalex KT88 as well as the Svetlana's... however in my instances, the bass was not controlled the way I would like it to be.

Good luck on your journey. This is the joy of tubes... you will prefer one or the other!

I have some nearly new Ei KT-90 type 3 tubes and all four of them make some noise as if a little part is loose or something inside. You move them and a tinkling sound can be heard inside each tube. Is this normal?