I owned older ARC, before the 6h30, but run a line stage, the Veloce Lithio, which does use that tube. I had a NOS quad of the DR Reflektor which sounded better, and when I was "fettling," thought those might be past prime time; tried a set of new production from Russia and at least in the Veloce (configured as more up to date, with newer battery pack and circuit changes), the modern tube sounded dead and flat. I did find a quad of old never used DRs from the late ’70s that make music. I understand that some ARC users don’t hear that much difference between the DR (how old?) and modern Russian tubes- you are limited to Sovtek or EH as far as I know unless you plumb the depths-- and those can be counterfeit or late production.
I say if you can’t hear the difference, you are probably fortunate. I think that tube is a dead end, given the difficulty of sourcing it.
