Hello, i want to install rich mod ii type ppimv in my 1959hw but i heard it would be better with some type of variable nfb and i have few questions. If i want 3 way switch than what values should resistors for nfb have or if i use potentiometer what value should it have? And if it would be pot then from which way signal goes in pot and which way out from pot signal goes back to circuit? And where should be pot grounded? I know which lugs are for in, out and ground in pots i don't know where it goes in the amp.