My ownership of the JL1 LE amp has changed my appreciation towards "hi-fi" listening experiences. I have been fortunate to own or home audition many amps; some solid state, but mostly tube. Jadis, Conrad Johnson, Lamm, Lectron, Krell, Classe, Mcintosh, Gryphon; these jump to immediate mind. All of these amps were quite satisfying. Some more than others, but all had their individual short-comings. Excelling in certain areas; whether that be tautness of bottom end, inner detail, extension, speed, etc... and showing less refinement in others; i.e. bloated bottom end, small soundstage, overly detailed, and on and on...
The CAT, within my system (as in my other posts, I cannot overemphasize the consideration "my system") has somehow brought out the near best of all the previously stated amps, with the least trade-offs. Driving Avalon Ascents through Jadis JP80MC preamp, with Clearaudio/Helikon analog and Sony SACD up front, I have enjoyed my longest run of fulfilling listening. Although vexations have diminished, I have not deluded myself into believing the Holy Grail has been sipped from. It's just so much closer than ever before. Much experimentation with cables and limitless tweaks have helped squeeze out added nuances , but this Cat amp with these Avalons are as musical, without sacrificing detail as I have experienced.
The most noticeable insufficiency within this system rests in the ultra bottom frequency extensions. The deep authoritative growl I have heard with some solid state, and of course, live music is non-apparent. It's difficult to locate the culprit without individual substitutions, and truthfully, at this juncture that rather minor( yet ever-so noticeable) flaw is easily transcended by the overall presentation.
An older FI review better describes the attributes of the CAT amp. I have not had the opportunity to run an Ultimate in this system, with many privy to the synergy of the combination pressing me to try. I also have no personal experience with the stereo amp.