CAT JL-2 amp upgrade

I just purchased the CAT JL2 and am also trying to determine from people who have had the upgrade to Sig to describe the improvements and quantify the improvements (obvious improvement, subtle improvement, etc.). The person I purchased the amp from (a dealer) said that he has the new Sig but doesn't hear much improvement so far.
The Sig isn't really broken in yet but he will let me know when it is. My thoughts on the JL2 versus the Manley 350 monos I was using are as follows. The Manleys have a much fuller (sweeter, richer) sound across the spectrum (I prefer this), the JL2 sounds lean in comparison. Where the JL2 betters the Manley is in detail, transparency and coherence at high SPL's especially with large ensemble bands. I think where the JL2 gets this tendency toward detail and accuracy is from the output tubes (6550's). VTL used to use these in their old 300 monos and when they switched to KT90's the sound became decidedly more musical.
I did almost immediately get rid of the sovtek 6922 input tubes in favor of Amperex SQ 6922 made in Holland (nice improvement). I also replaced the stock EI 12ax7's with Amperex 12ax7 D getter long plates also a nice improvement.
I have some Amperex 12au7's d getter long plates in transit. For my taste the Manley was a better match in terms of musicality but the CAT does everything else better. So I guess I will start down the path you have travelled John. Finding a preamp (to replace the CAT Ult MK2) with full textural qualities to mate with the CAT's somewhat analytical presentation. Johnny, if you got the MK2 upgrade for 1000,
you did well. Ken told me he is charging 3000 for that upgrade and is urging people to do the Sig upgrade for another 2000 which is much more comprehensive

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

Pubul57,

I haven't tried any other preamps in the system yet. I wanted to hear the Emotive Audio Epifania ($25G) but the dealer never followed thru on his promises to bring one for a brief audition. Other posters have found the Aesthetix Callisto to be an excellent match for the JL2/JL3
amps. Many posters have decided that the CAT amps need a harmonically rich tubed preamp to balance what they find a
dynamic and detailed presentation of the amps. I have found from EXTENSIVE tube rolling in both the CAT Ult MK2 and the JL2 amp that the combination of the two is excellent. I can easily push the sound from overly textured (soggy classic tube sound) to overly detailed (hard and etched) and all points between these extremes with tube selection. I have found tube combos that strike an ideal balance (great texture, depth and soundstage combined with loads of detail and huge dynamic swings presented in a gorgeously relaxed fashion). Both the CAT pre and amps are very transparent the sound presentation is determined thru tube selection. Bugman03, I don't understand why you think the JL2 has insufficient damping factor when used with the Eidolon. The bass I hear with the Osiris is very good. I ran a pair of the Levinson 436's before buying the CAT JL2 and the CAT beat the Levinson in all parameters but especially in bass control and extension. From my experience, the Avalons work better with tubed electronics. My old pair of Manley 350's
also easily outperformed the Levinsons. Before all the Spectral and Rowland users comment, I have heard the Avalons perform very well with those SS amps, just not quite as good as with tubes. Bart