This is what i have been working for a fellow AKer for the last week with a pause for the transfomers and chokes to show up . http://www.audiokarma.org/forums/in...ore-out-of-the-8600-series-a-lot-more.665735/ The is based on David Gillespie's work , i modified the power supply with a second choke and a star ground for all high current ground . I also used parts on hand and changed the cathode resistors and pots to 100 ohms for or a total of 200 ohms adjustable from 100 to 200 ohms to set the bias . I moved the test points to the front of the amp using a 9 pin socket , i replaced the 9 pin socket with a better one with a shield and wired it for a 12AX7 instead of the 6EU7 . when rewiring the 6CA4 socket i broke a pin off and replaced the socket with a better used one I was double checking everything and noticed i switched the output wires , i'm used to everything as black to ground , that i did it automatically, will fix that tomorrow before i test it out . Have a metal shield to put between the second choke and the output transfomers if need be , .The second choke will have a near constant current and voltage on it , with the amp being class A so the magnetic field should be fairly constant .