Huh, what a day... I tried some ideas in a hurry in my super-equiped electronic laboratory. Good news are that modified cascode 5687 driver for 300B works, measured values are very close to calculated/simulated, and the sound is "promising". And then - electric shock through the chest (both hands, of course)...not a big deal, just a little chest and head pain...
I`ve continued with experiments, but then - big HV toroid starts to burn...no big deal, not too expensive. I bought four cheap multiple secondary toroids some time ago, one shorted (primary) after about an hour, and then today I burned another one (primary too)...people who made them don`t know what they are doing, for sure.
Before you start to complain that maybe hurry and wire-mess, and cheap parts aren`t the best way - please remember your faults...
(Part 5 - cascode driver coming soon

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