Mike, unless I missed it, you need a custom tube playback head outboard preamp for your Ampexes.
@inna
you missed it. :-)
done and done. both my Ampex ATR-102 decks have MR-70 Nuvistor tube preamps. both decks have direct out from the heads into the outboard preamps, one box per channel. the top pair for the 1/4" deck on the left, and the bottom pair for the 1/2" deck on the right. i have a switch behind to go back and forth. the decks and preamps are hot rodded. read the first post of the thread which describes the level of upgrades.
the MR 70 is a legendary late 60’s super deck. if you scroll down on this thread page you can read about it’s history.
here is the thread about it.
https://www.whatsbestforum.com/threads/ak-hot-rodded-ampex-atr-102s-w-mr-70-preamps-replaces-my-studers.36288/
here is a current picture with both decks and the -4- MR 70 hot rodded preamps on a rack between them. the MR 70’s surpass any newer custom output electronics.
https://www.whatsbestforum.com/threads/ak-hot-rodded-ampex-atr-102s-w-mr-70-preamps-replaces-my-studers.36288/page-6#post-874901
as great as my -3- Studer A-820’s were with the King Cello preamps, this set-up is in another realm.