I will hopefully get to installing the IBBA this weekend. From your schematic for the EFB circuit you reference biasing output tubes to 21ma. I first rebuilt my power supply and the majority of the 400 with Jim Mcshane's kit & then followed with your EFB, Power Supply, Control Section & SS Buffer. I currently have the original fisher output tubes installed what would you recommend for bias current? im also considering a new set of TungSol 7591's what would they get biased at?