The Valve Workbench is developing and providing some practical insight into the process of modelling valves.
In Designer Mode it currently allows you to choose a triode model and use it to calculate the operating point of a common cathode circuit – it also plots both anode and cathode load lines for the chosen device. Further development will, of course, see other circuits added with the pentode common cathode being next on the list.
In Analyser Mode you can create measurements of both triodes and pentodes that can then be saved into modelling “Projects” or simply used to assess device performance (e.g. for matching).
In Modelling Mode you can use measurements taken from the analyser to first create initial parameter estimates and then do a full fit of the measured data to a model. Currently, the modelling only supports the use of anode characteristics for modelling triodes but this will also be expanded, in due course, to include pentode modelling.
One thing the experiments with modelling has thrown into somewhat stark relief is the fact that the Valve Analyser needs to cope with a wide “dynamic range” of anode currents across small signal and power devices. As a consequence, I may have to next devote some time to building the second iteration of the Valve Analyser hardware that uses the Arduino Mega and provides a third range for measuring small anode currents with greater resolution.