you may want to try some EL34s' as well. I use EL 34s' in my JA 30s' and Ja 200s'. I haven't tried any KT88 or 90s' but I really don't like the set of 6550s I have for the JA200s. The 6550s have a hard edge to them.
Good luck.
Good luck.
JADIS JA80 with 6550 or KT 88 or KT90 ?