It doesn't really have a regulated screen supply. As you mentioned the OC3 is really like a zener, gives about 115V drop from the plate supply. This was done in other examples of pentode amps too, using other means. I've seen a voltage doubler for the plate and a the center of the doubler used for the screen for example to get the drop. I'd like to know what the difference in the tube performance is with this lowered screen value wrt distortion, power, etc..KT66 wrote:Interesting. What exactly is the purpose of that Leslie amp ? Must be a clean machine w/ the regulation and local feedback on the power tubes, and what's with the CT on the OT secondary ?
As regards the OPT center tap, check out the Leslie 145 schematic. It uses the center-tapped secondary for series voltage feedback to the output tubes' cathodes.