Indeed I was wondering if they had higher quality parts and better parts matching, including for all the tubes including the 50CA10 output tubes.
One other characteristic feature for the Ultimate, at least for the lx-38 integrated amp and cl-36 preamp was the lacquered wood cabinet. It is the nicest cabinet I have ever seen on an audio component.
I believe these were manufactured in the period just before Alpine purchased Luxman. Very difficult to get more information. I’ve reached out to some Luxman experts with no success.