I understand that...
"What I read often, and find disheartening, is someone posting looking for knowledge / insight with specific questions about how a given tonal mechanism works and invariably getting the nevermind how/why "just use your ears / set it to what sounds good" responses
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... can be disheartening at times. But part of the problem here is that there are often many layers of knowledge that are necessary to fully comprehend how certain mechanisms work. One thing that is not really stated enough here on this forum (as far as I am concerned) is that it is very easy to hit the wall in dealing with the AxeFx products without having a pretty good understanding of how (in particular) tube amplifiers actually work and how their somewhat different designs exploit the fundamentals of the mechanisms involved.
I'm not just talking about how to turn the different knobs on an amplifier. I'm talking more about the fundamentals...
...how transformers work, how linear power supplies work, how inductors and capacitors work in different ways for different purposes in amplifiers in relation to the other components in common audio circuit topologies, how resistors are used in various ways, how basic filters work, how both negative and positive feedback (stability and oscillation topics) works within those topologies, what the real difference is between Class A and Class AB power topologies, how impedance matching devices work such as output transformers, how speaker motors work, what the difference is between voltage amplification and power amplification, how tubes, both preamp and power tubes work and how they are biased in different ways and what that even means, what triode, pentode, and ultra-linear operation is, how the circuits in your guitar are interfaced to the amplifier yada, yada, yada... There are lots of good books and net based learning tools for this.
The point is that if you don't understand the fundamentals of all these things it becomes increasingly difficult to describe some of the mechanisms in the AxeFx that attempt to model and provide (often extra) control over many of these parameters. And this doesn't even yet address the whole world of effects and how the fundamentals of their designs interface to the amplification signal paths.
So when someone puts you off with a short answer and to use your ear, please try to understand that they may simply be saying that you may need to do a little (or a lot) of homework to really makes sense of an answer that might otherwise get very involved in the necessary fundamentals to adequately describe a given mechanism. Often this does require that your ear is also trained to discern the difference among many different fundamental audio mechanisms so that you can learn to predict what some abstract circuit definition might sound like as fundamental mechanisms are piled on top of each other in the overall signal path that you are working with. Hope that helps? Maybe?