Thanks for the information Randalleron! Personally, I use the Ei KT90s in my Jadis. Perhaps they use 6550s from the factory that produces the Golden Dragon line(Shuguang???). I have never gotten open sound from Chinese tubes, but have never tried Golden Dragons(they are supposedly excellent). Usually the Chinese tubes impart a very slow sound, as if a thick oil had been poured over the music(I am sure Jadis would not go for this type of sound, as they are not fond of "warmth"). Moving to European tubes seems to open everything up. I do not like the sound of 6550s, finding them inferior to: KT90s in terms of power, bass response, extension, and tone(besides the fact that KT90s supposedly are much more long lasting); and KT88s in terms of sweetness, warmth, and "glow". I prefer using KT90s in more neutral applications, and KT88s in more romantic ones. But, we all have our preference... Good luck!