Thanks 42. Yes im using the A connection. and I was begining to think that the pin 3 or 5 is the cathode. It somehow interlinked with the filament? I wasnt sure which one R4 or R3 to play with but will have a play in this area. Since my post I have been playing with a standard 12AX7 and this has lead me to understanding a lot more about how the tubes work. the 6418 is a weird thing and no doubt not the best place to begin the newbie curve