Recently picked up a 1959 Ampeg Jet that came from the factory with 12ax7's instead of the standard 6sl7's. I've seen tube charts on early Ampeg Jet's where 12ax7 was crossed out on the tube chart and 6sl7 was written in but I've never actually seen one that had the 12ax7's. The tube chart on mine list's the 12ax7's but the schematic pasted to the inside of the back panel is still for the 6sl7 equipped amp. Also the first 12ax7 seems to employ grid leak instead of cathode bias like ive seen on the regular 6sl7 jets so it doesn't really follow the schematic. Anyone know anything more? As much as I can find this amp doesnt exist.