>Hello Bill: > >The circuit will work only for tetrodes that have screens and control grids >that can dissipate a large amount of power (many watts). Thus, the 4-400 >and 4-1000 will work fine in grounded grid. > >None of the ceramic tubes will do this (Maybe a 4CX10000 will). ** it will. A pair of 3-500Zs will drive one to c. 18 out with a 9kV anode supply. >... - Rich..., 805.386.3734, www.vcnet.com/measures.