I used to hang out at the Ampex Newsgroup run by Howard Sanner. You might check to see if it is still functional. All hardcore Ampex guys running everything from the last Ampex stuff to the first Ampex 200. I learned a lot from those guys. Do a google search for them.
Donw in my basement I have about a dozen Ampex 350 and 351 machines in various stages of needing attention. I will get around to tweaking on them one day. I keep a set of electronics in good shape for preamps. I would safely guess that just about everything you heard done in a pro studio from the 50s through the 60s was done on Ampex tube gear.