TubeWork RT2100 Schematic - Please Help

[SamRE]

Hi All,

For the past year or so, I've been trying to reverse engineer the Tubeworks RT2100 Mosvalve amplifier from it's schematic, cause I wouldn't mind either A) Building a Low-power version, or B) Condensing it into a lil pedalboard PA or line driver.

The problem is that I cannot for the life of me figure out the following:
. Where the negative rail (TB-5) for the valve stage is.
. What the value of the Elec cap between the cathode resistor/Grid-leak junction and ground is.
. How, on gods green earth does the channel switching work??

I have tried to LTSpice sim a lot of it, but It is largely pure guess work.

If anyone has a better schematic than the one I have attached, some understanding or experience w/ the hurdles I've come across or has an answer, I would be very appreciative.

TubeWorks RT2100 Schematic.pdf