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

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.

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.