cj Amps were MV series I thought & the PV series were their pre-amps. I could be mistaken
it's been known to happen. Exposed tubes is possible but not always a design feature.
The OP has asked for traditional i.e., warm tubed pre-amps with exposed tubes.
Bottle head, ASL, Maple, Response Audio had a variety of pre-amps over the years
which might fit the bill.
Good luck.