Conceptually, these design calculators are similar to the excellent work of Giuseppe Amato but have a slightly different philosophy:
The javascript to model the valves allows a variety of different model types to be supported - the API simply requires you to be able to determine anode (and screen current) for a given anode voltage and grid voltage. By default, I use a Cohen Helie model for triodes and a modified Reefman (Koren derivative) model for pentodes, but support may be added for others (e.g. Immler) in due course. In general, the operating point is found by finding the intersection of the true load lines, noting that cathode load lines are not actually linear.
To use the calculators, simply choose the valve you want to work with and edit the default component values to suit your needs. Any change will cause the operating point to be recalculated and displayed.
The following design calculators are provided:
Triode Common Cathode Amplifier
Pentode Common Cathode Amplifier
Long Tailed Pair Phase Splitter
Cathodyne Phase Splitter
Ultralinear Single Ended Output Stage
Ultralinear Push Pull Output Stage
In addition to the design calculators, the Generic Characteristics visualiser allows you to simply plot the anode (and screen) characteristics for any of the supported tubes.