From a few cascode-able valves like 6BQ7 and 6DJ8, the schematic shows a pair of triodes stacked on top of each other and the upper grids attached to a voltage divider reference.The composite valve behaves like a pentode. So what happens if you sub the top triode for a pentode? Use the same voltage divider for the control grid, dropping R and bypass to its cathode for g2 and what does it do now?
How to model this composite? I know how to gneerate the composite's plate curves for any pair of triodes, but the triode/pentode combo looks a bit more complex...
thanks,
Douglas