Hey, I'm building this simple tube amplifier amplifier as a warm up to some hopefully bigger and better audio tube projects. http://diyaudioprojects.com/Solid/12AU7-IRF510-LM317-Headamp/ I realize the LM-317 is configured as a charge pump but I don't exactly understand its purpose, Could it not just be replaced by a higher rated resistor? Is it just to utilize safety things such as the regulators shutdowns? Also, Am I correct to assume the tube is the "pre" stage and the fet is the power stage? Sorry if these are silly questions. I'm a student and basically only know classic configurations of these parts. Another question about tube amplifiers or just amplifiers in general is the p-max line what is considered "headroom" when driving a speaker? or is it less about power and more just about the 1db saturation point of the amplifier? Thanks!