Upgraded all other resistors to 1w carbon film today, except those 4 in PI (470, 1m, 1m, 10k) since I figured they arent getting high voltage so carbon comps will be fine. And redoing that 4 component turre would have been pain.
I had some motorboating at high volumes and whoa, the 5.6k grid stoppers were 5.6ohm!
Replaced those with 10k's I hd in hand and the motorboating and standby popping was gone! Lesson learned: always check your resistor values twice.
Then I to the mixer cap to 500p and didn't really like it. 560 is much crisper, more alive. I'll put that in again.
So, the spec I'm running now:
bright ch coupler .0022uf
tone stack 33k/560p
Output couplers .022uf
It's sounding pretty damn good! I might still change preamp filter but I think maybe the 50/50uf is making my fat cap work so well. It's not flabby at all even when bass is dimed, but balssy with punchy bass.