My take on Jazz at the Pawnshop is that I like it because it is "fun" music. The high-end is much better than the bottom end. I made a 15 ips 2 track recording from my LPs that contains side one from Sonny Rollins Way Out West which is followed by Jazz at the Pawnshop. After you finish listening to Way Out West and JATP comes on, you are bass starved. The bottom end is rolled off (at least on my copy) of JATP. Way Out West pretty much shames most recordings though.
Did I read somewhere that JATP was recorded on a Revox A-77 tape deck and played back through a Dynaco ST-70 amp?
I think Proprius used modded B77 while Opus 3 used an A77. Could have it reversed though.