FYI, last time I looked - admittedly a while ago now - DRD did require a conventional SE "large output transformer."

IIRC, DRD has two "clever tricks": 1) recycles some output stage current for the driver (via a plate choke) and 2) uses a cap (oil preferably) from the top of the output cathode R to B+, ancient WE style. The means a little lower current draw on PSU, should be less heat in output bias circuit (I think), less PSU in signal path, and DC coupling. This should add up to more modern performance than ye olde RC coupled circuits with premium-ish parts at (probably) less cost. I would do things (only) a little differently than the DRDs I have seen however...

I am in no way associated with those making $$$ from these designs - just willing to acknowledge something clever - if not all that new.

Cheers
Ray