I've built a replica of an amp guitalogist made a few years ago:
but I can't figure out one thing, and it's the only thing he didn't really show, is the NFBL switch, it has 3 positions, on-off-on, he says that "it switches between 2 NFBL resistors, you can also put it in the middle where there's no NFB"
which would make me think he has a resistor to ground before the switch, because originally the amp got the DC bias on the PI trough the OPT.
here's the shematic of the output of his conversion of the amp that was last filmed (only thing he changed is coupling cap values from 47nF to 100nF)

the original amp was a Grommes-50PG2 (or PG3)
here's my best guess to what he has done with it,

maybe you have a better guess to what he did with the NFBL switch.