These are plots provided by VST Analyser (
Christian's Blog » Measurement). The one on the left plots the frequency response, the one on the right plots the harmonic saturation level. The plot on the right the key thing to look at is the Klirr Factor percentage, as it denotes the amount of harmonic content within the sound as percentage in relationship to the fundamental. In the Nebula GUI, the DRIVE function relates to an equation that relatively raises and lowers the volume of the harmonic audio kernels - in this case harmonic orders 2 through 8 - while keeping the fundamental (audio kernel 1) at the same volume. In the default setting, I liked it best around -10 dB, which results in a Klirr Factor percentage of roughly 7%. On average, normal hardware EQ and preamps typically float from about 1%-15%, with the majority of the solid state ones landing around 2-3 percent at nominal input and output levels.
Harmonic saturation as it is supplied by my libraries is limited to the Nebula version only. Convolution Reverb is not capable of conveying this and other non-linear behavior as a technological restriction. One can write a loading program that adds this (of which there are no DAW based plugins that I am aware of that do this, however I am under the assumption that there may be something of the sort in the Axe II cab block) in addition to the IR, but is not based on the captured audio, just estimated as a generalization.
Fat and Warm are treatment options available for all formats. My Nebula implementation simply has the added convenience of interpolating the values between the set sample points on the fly without the need to mix separately - built in mixing capability I guess you could say. Much of this will make more sense when I have everything compiled, packaged, and finalized, which I still need about another day and a half to do properly.
