It looks like this parameter was introduced in Firmware 17. But I never noticed it before. In Axe Edit it appears on the Power Amp page of the Amp Block editor. Evidently this is modeling the Presence Knob Pull/Shift circuit that, iirc, was part of the power amp section of both the Mesa MKIII, the MKIV I used to own as well as the Simul-Satellite I still own. I always had this control in the Pulled or active setting. These amps simply sounded much harsher and less musical without it active. This is true for cleans as well as for overdriven tones. After discovering the switch inside the model my Mesa lead tones are finally making more sonic sense to me now. There was always something I didn't like about the results I was achieving via any of the Mesa models. I think this Presence Shift switch may have just changed all that for me. I was going to suggest/request that Cliff think about adding it to the IIC+ and USA Pre models, but I guess that doesn't make sense since neither the MKII power amp sections or the 2:Ninety power amps had this circuit. But when I had a Triaxis it was paired, usually, with my Simul-Satellite which does have the circuit and which I always had activated. I always thought of the Satellite as being a mono version of the 2:Ninety w/o the extra foot-switchable features. But I guess that was off since a real 2:Ninety doesn't have Presence Shift. The Satellite series were originally conceived of as a way to have the MKIV tones in stereo which is why they do have the Presence Shift switch I guess. Still, for me, it might be useful to have this in the USA Pre models too, anyway. And since I always had it activated on my clean channel tones as well, for me, it might be cool to have it in the USA Clean models as well. And while I'm discussing the USA Pre LD models... Does anybody else find these models as being too gainy? With Vol and Gain both at 5, my real Triaxis never had that much gain. I have to lower Input Trim to around 0.250 in order to get a similar gain structure to what I remember from my real Triaxis. I know that Cliff owns a Triaxis and that he's checked and rechecked the models several times over the years already. But it does seem off to me. I've not been able to recreate my old Triaxis tones very well on the Axe which surprises me.