Johnny, thanks for the info. Has anyone experimented with tube rolling the output tubes in their CAT amps? Ken told me I was asking for trouble and I would end up blowing up the amp. I ordered the SED Svetlana 6550C tubes today from Upscale Audio. Kevin from Upsacle gave me a similar warning as Ken's about fooling with 6550 variants (KT90's, KT88's etc.)in CAT amps. I have got to say as I am listening to the CAT JL2 right now that the improvement from changing the 12AX7's and 6922's has made the amp much more musical and when my Amperex 12AU7's arrrive it should add more musicality to the presentation. I am very happy with the sound right now. My JL2 sounds very quiet, I don't feel the need to do the upgrade to improve performance in that area. My previous plan was to find a preamp to replace the CAT Ultimate MK2 to increase the musicality of the presentation but I am rethinking that option now. I may turn my attention to the digital front end instead.
Bart
Bart