The scary thing I've learned is that a lot of these amp 'designers' don't really even understand what they are doing. In fact the schematic I got from the designer was a JTM45 schematic with markups. Another popular new amp is basically just a JTM45 clone with a couple minor changes. For example a Bogner is basically a boosted Marshall with a different treble pot taper. You can make almost any high gain amp sound like any other high gain amp with a few EQ tweaks which is basically what the designers do. Truth is amps are more similar than people think.

So to accurately model the control behavior we need a schematic and the actual amp (as the schematics often don't indicate the pot tapers). The problem is then people go 'the model doesn't sound the same as my amp if I turn the drive all the way up and bass all the way down'. controls behave the same it's much easier as we have software that learns the input EQ, output EQ and gain. If you don't care if the tone, drive, etc. 'The hardest part of modeling an amp is getting the various controls to match the actual amp. Overview of Fractal Audio's advancing amp modeling, starting with the Axe-Fx II, based on the firmware release notes and quotes.

4.16 Firmware Ares 1.03 for the Axe-Fx II.

Bias guitar amp designer