hey there,
i just wanted to share my experience and observations of profiling a few different higain amps. since i've been profiling through my isocab and using studio headphones for almost a year know, i've got quite used to hearing the kemper as well different amps.
in general, it seems that the soldano family of circuits is what can be profiled most accurately by the kemper. i used to own a 92 hotrod 50, and now still have my SLO100 clone and a dual rectifier (it's 90% SLO after all). the distortion 'character' of these amps seems to be profiled quite accurately by the kemper when not using too much gain. all in all, there always seems to be a slight loss in bass/low-mids in the kemper as well as some 'air' that gets lost. both things can be adjusted afterwards and would become negligible in a mix, anyway. which is why the kemper works so well after all.
now with the two Diezels i have at home (VH4 and Herbert), the kemper simply fails to nail the trademark diezel midrange compression. the overall frequency spectrum is captured accurately, it's just more of a 'feel' thing. i know people will shout 'clips!', but this simply doesn't not reflect how an amp react to your playing (compression, sag, etc).
bottom line is that seeing that i believe the kemper was developed using a recto/SLO type amp for matching higain distortion. in my opinion the unit works as well as advertised with these amps, but unfortunately fails with some other specific amps. knowing a fair bit about amp building, i can imagine that both scenarios (SLO and Diezel) can't be matched with the same algorithm. the SLO has four stages of cascading gain with a cold-clipper, whereas the diezel uses three stages driven VERY hard.
i'm going out on a limb here, but i'm assuming that the profiling algorithm is not accounting for the behaviour of the individual gain stages in the amp, but rather the net sum. this would also explaing why profiling an amp with a boost in fronst doesn't work so well...
i wonder if other users have similar experiences to mine.
:2cents: