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

The pre will arrive in 2 weeks. So i decided to pull 4 of the 6550's in the Defy and swap out the KT90's in the JOR. Man I sure hope the Defy does not sound like the JOR with 6550's. Because if it does I'm not going to like the Defy with 6550's for my classical. Way too tubey and bloated, all the fine definition and sparkle from the KT90's was gone. I guess I'm going to need to buy ...12 Czech KT90's. Gonna cost me a bundle. Any suggestions?
can anyone put me in touch with a dealer for the high quality czech KT90 tubes? Gabriel wants an 'arm and a leg" price.
Sorry Bartokfan, but Ei made the only KT-90 worth troubling with and as you well know they are no longer running. The Jim McShane modded, vintage HK Citation amp owners snarfed up the rest (check with Jim McShane Google him). The current KT-90 is supposedly really poor. My very strong suggestion is to have it checked for Mods. Many Jadis have been modded into sonic torture machines, unless you bought it new and that is well....that. Otherwise have it rewired for EL-34s and live happily ever after. I have heard the difference the after is glorious.
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.
Joe, I'm looking into the Telsa EL34's, the ones you suggested to me last yr for my JOR. Correct I did not bias the JOR to the 6550's. I just simply took 4 of the 6550's out the Defy and pluged them into the JOR to get a idea of what i'm in for.
"most unlike tube sound...flat and dead sounding" Pretty much what comes across with the 6550's in the JOR. Not sure if I should listen to newbee or your suggestion to try the EL34's. The only reason I bought the Defy is to have what the JOR delivers but with more power. I was not aware that I would have trouble finding the Ei KT90's if I wanted to roll tubes.
FWIW, In my post I made NO recommendations, just gave you some info to consider before you commit yourself to tube selection or amp modifications.

FWIW, from your comments about the sounds you want from a tube amp, including your selection of small tubes (Sovtek 6922's) and KT90's, I have no confidence that you will ever like the sound of EL34's or E34L's, much as I agree with Joe about thier sound quality (I find they can produce a very crystaline, crisp tone, a sound which many would admire). Some how I expect that you would not enjoy the sound of an amp that either Joe (forgive me Joe for being presumptive) or I would chose. That is why I made no recommendations

I use EL34's, 6550's and KT88's in amps successfully, to my ears at least. The one tube whose sonic signature I don't like is the KT90 (and I have amps designed for them with their original EI KT90's essentially unused.)

BTW, you didn't mention the brand or age of the 6550's you used, but there is a fair difference in the sonics of the brands. Some are warmer, some are brighter, etc. Perhaps that is also an issue for you to consider in making a selection, and as Joe suggests this character can be changed by appropriate small tube selection.

There are a lot of ways to skin this cat...........

Nicely done, Newbee!

One thing I just wanted to put out there is that my perspective comes from learning the hard way. I have owned three Jadis integrateds: a JOR that I bought new, and a DA30 and DA60 that I bought used. The only one that was right was the JOR.

I had to put almost a grand into the DA60 to get it right, before that, it was about as bad as bad could be. If I didn't own a JOR, I could have chalked up the sound to Jadis being horrible amps. When I found out the history of the amp, it turned out a very well-known invididual who is considered a true Jadis guru "improved" it. In my mind, it was rendered almost doorstop status. After I had it returned to stock configuration, I ended up with an amp that I consider a lifetime purchase, and how much is that worth?

The DA30 is also very, very wrong. Haven't gotten that one straightened out yet, but I will at some point.

Both the DA30 and DA60 looked like they hadn't been modded. Definitely caveat emptor when it comes to buying a used Jadis.
Really excellent advice from Trelja and Newbee. Suitable for bookmarking for Jadis fans.
Interesting comments. Seems I've read similiar comments on differences in Jadis' models....anyway I could also make comments on at least one other famous tube amp manufacturer, american. That I have issues with the sound. So I'm not going to knock Jadis, based on experience of other tube amps.
The KT90 can be a tad 'steely' as i mentioned. But it does have nice separation of bass, mids, highs. Highs roll a tad, but hey its a small trade off for its other qualities. So seems my first Jadis purchase was a good one, JOR/KT90's. Now the JOR with other tubes might be exactly what others need for their style of music. I'm just saying what works for me. Though i am willing to give the stock 6550's in the Defy a chance. btw the 6550's are what Jadis stocks, the Svetlana/russian /SV6550C tube. The tubes look awesome. Obviously I was wrong in "testing out" the 6550's in the JOR w/o proper biasing. Jadis biased the Defy 7 for the 6550's at their lab. So I'm in for game. btw the pre is the Ming da 2A3 which I will let Ken here in BR set up on his system first as he has multiple pres to compare with. This way when we hook up the pre he can tell me whats going on with what. If there is an issue he'll know how to track down some adjustments/roll tubes. Like Joe just mentioned, how much is it really worth to us. I'm trying to make this my "last amp". Also note: IF the JOR came with the 6550's and the amp sounded like this on orch, I'd sell it immediately. I mean its bad, as in poor, not "bad" as in street lingo.
Great thread, even though I have never owned a Jadis component, I recognize a few of the posters here and thought I would second Mechans and Newbees posts. There is a tremendous range of tuning to taste that can be done with signal tube rolling. I have an old Manley 350 monos
in the closet (currently run a CAT JL2) that use the first generation EI KT 90. A great output tube! The Manley's sounded better than the JL2 (both with stock signal tubes)
when I initially installed the JL2. I have done a massive amount of signal tube rolling in the last year. The CAT is now at a level the Manley could never reach. I have to mention Trelja's post here for a moment. He refers to the 12AX7 position having a bigger impact on the sound than the 12AU7 slot. When I began rolling the signal tubes in the JL2 (12AX7, 12AU7 and 6922's), I had the same impression about the 12AU7 slot. The differences heard in the other two positions were much more pronounced. It took a lot of perseverance to get the dramatic improvement from the 12AU7 slot that I had achieved from the others.
A quick side point to Bartokfan. If you are using the Sovtek 6922 in front of the KT90, that steely sound you hear (and attribute to the KT90) is coming from the Sovtek (the worst 6922 I have ever heard). The best of the signal tube families IMO is the 12AU7 family. There are an almost limitless amount of tuning options in this family. I will never finish this post if I try to describe all the signal tube options here. I posted a lot of my thoughts on them on AA under the moniker posbwp55@msn.com. What really drew me to this thread was a google search for Ming Da 2A3 preamp. I have heard it is a giant killer. I am currently using the CAT Ult MK2. I will probably try to get a 30 day audition soon. Bartokfan, when you here more about this pre please post it here. I am unfamiliar with
the 2A3 and 6SN7 tubes used in it but it does use the 6922.
If it is close to my CAT with the stock tubes I guess I'll have to figure out two more tube families (oh no $$$). One quick comment on the 12AU7 of choice, all you guys that haven't heard the E80CC in this position are in for a treat (Tungsram). It is not a direct replacement, but I have not heard of a circuit it failed in yet.

Posb My friend here in BR has the Ning da 7 pre that he is modifying , p;us a Redrose Levinson pre. I want him to test my Ming Da when ever it arrives. Be prepared to wait, I ordered mine 1 month ago, still waiting. I think once this pre hits, it'll be take a number, stand it line.
The Sovek 6922's improved over the stock Jadis, and its not like me to start investing in pre tubes. I'm sure there are better, but I'm happy with the JOR. I think I need to re photo my amp for sale, complaints about the dust factor on the amp.
I'll post a review of the Ming based on Ken's comments on his system, uses the Vandy 5's. and on my syatem as well.