Here's where I'm getting that R2 stuff:[attachment=o213389]

[attachment=o213390]


Here's the TO-3 heatsinks:[attachment=o213391]

Looks like R2 is like a trimmer to make the voltage variable(?). Of course, once it's dialed in you can measure the resistance the pot's providing and replace the pot with a fixed resistor, unless you want to be able to change how much your blues are putting out, for example. Somehow I think PWM might be more efficient at doing this, but I'm not that far along yet.