6550 vs KT88 vs KT90

I'd suggest you ask the manufacturer of the amps directly. The new Jadis have transformers optimized for the KT90s, but I believe that VTL amps can use both 6550s and KT90s, so I don't know if you have to have a transformer specifically designed for that tube. The manufacturer will be able to tell you what he/she thinks is the best tube for your amps.

I second the vote for the Svetlana KT 88 vs 6550 (haven't tried KT 90's). Just retubed my Aronov monoblocks with KT 88's from Upscale Audio and the improvements in the midrange and the top end are dramatic. If the bottom end is less defined, I sure don't miss it. Then again, my monitors only go down to about 45 Hz, and rest is handled by a powered sub.

There is so much good information on this thread that I made a hard copy of it-- thanks everyone. Craig.

Many thanks to all on this thread and especially to Trelja who REALLY knows his tubes. This is what all the threads should be like. Mark me down as another happy KT88 owner. Anyone for driver tubes?

Trelja, just a note to you to mention that Jadis replied that the KT90s can be used in my old JA80s. I may get a set for when I run out of the NOS KT88s. Anyone with experience on how the new KT88s stack up against the older ones, sonically?