while waiting on a preamp for my DEFY 7/6550's

Interesting. No wonder I do not see any EI KT90's for sale. The Ei KT90's in the JOR do well with orch and any other music for that matter. I'm still hoping Pierre has some laying around. I see the EL34's tube is shaped like the KT90 and as you suggest this may be my best option, my only option. I hope the local tech guy here in BR can bias it to the EL34's. I'd hate to ship the 135 lb amp. The 6550's made the JOR sound like "most other" tube amps. A sound I could not live with. I doubt if any bias would make substansive improvement. I hate anything "warm and fluffy" in a tube amp.

Yes I see Svetlana EL34's new. This is the tube I will order.

If you hate 6550's compared to KT90's you're really going to hate EL34's. Compared to 6550's they are a warmer, 'mid-range magic' tube. Sounds nothing like the KT90 or 6550. Beleive it or not the 6550 (SED's anyway) is much closer to the KT90 and any of the other popular power tubes. Better do your homework before you jump off that bridge.

well maybe the JOR is not biased to the 6550 and thats why it sounded off. Hopefully as you say the 6550 can "pull off" big orchestra as I like it. The KT90's are a tad hard edged. But I like bass/mids/highs separation that the 90 offers. . The pre arrives in 2 weeks. I'm not sure how I can tell what component is doing what. IOW if there is something i don't like with the image, how can i tell if the issue is more with the pre or the 6550's in the Defy....I'll have my friend who knows his stuff come over and give a critque. Hopefully all will go well....

You are going to have to spend a bundle on Czech KT90 tubes. Personally, I've never seen a Czech KT90...

On a more serious note, tubes are made in Slovakia, not the Czech Republic. Ei KT90 tubes were produced in the former Yugoslavia, prior to the 1998 NATO bombing campaign. Not sure how the KT90 of today sound, as I haven't heard any.

To my ear, the 6550 is one of the most "untubelike" tube I can think of. I really find them flat and dead sounding. I do agree about the lack of resolution in general, but that also sounds like the amp is not working properly. The first two questions I must ask are, did you measure the tubes, and did you rebias the amplifier? Without knowing the answer to either of these questions, you're wasting your time by trying to draw any conclusions.

You must listen to The Doctor's (Mechans) advice. Unless you bought a Jadis new, or can verify its history with absolute confidence, you simply must presume it has been modified in some way that will totally and completely destroy the sonics. Until and unless you send it in to be gone over, forget about evaluating anything in regards to what it does or does not do. Yes, this is not going to be cheap. The shipping alone is going to be a bear. But, these products have literally been savaged over the years, and must be put back the way they were originally. Forget about whether it looks bone stock or not, without the schematic and the ability to check the voltages throughout the unit, you'll never know.

Personally, The Doctor and I have found the JJ E34L sounds best in a Jadis. For more bass, try a JJ KT77, but you'll give up a bit of the best midrange around. If you must have powerful bass with the midrange magic of the E34L, roll the 12AX7 and 12AU7 tubes, the 12AX7 being most important.

Not sure what the shape of a tube has to do with anything beyond having them fit or not fit into a component - not an issue with a Defy 7.