You should send an e - mail to Jadis.
In my queries to Jadis, they have only recommended two tubes to me(for several of their products). EL34/6CA7/E34L or KT90. They have told me the sound of 6550s is not as good, and their experience with KT88s have been horrific. Jadis used to be a proponent of 6550s before switching their allegiance to KT90s.
My feeling is that EL34s would be OK. Especially, if you like the sound(and that's what the picture showed). I presume the Defy 7 is autobias. As far as I know, the only Jadis amps which are not autobias are the Orchestra and Orchestra Reference, and they are perhaps the most difficult of tube amps to bias.
In my queries to Jadis, they have only recommended two tubes to me(for several of their products). EL34/6CA7/E34L or KT90. They have told me the sound of 6550s is not as good, and their experience with KT88s have been horrific. Jadis used to be a proponent of 6550s before switching their allegiance to KT90s.
My feeling is that EL34s would be OK. Especially, if you like the sound(and that's what the picture showed). I presume the Defy 7 is autobias. As far as I know, the only Jadis amps which are not autobias are the Orchestra and Orchestra Reference, and they are perhaps the most difficult of tube amps to bias.