>VU3RAZ wrote: >4-400 (4-400A?) . . . 450 V DC Screen . . . 130 W output. Your screen voltage is insufficient. Do you have the data sheet, with specifications for class AB1? I use 810 volts on the screens and get 1200 W from two tubes in push-pull. www.zianet.com/k5am/amps/6mkw.html 73, Mark, K5AM