I'd really like to know what went on here and hope that CK or anybody with technical knowledge of the profiling process can chime in.
I made a series of profiles using my old Marshall and a Friedman. I got quite a few very good results, with sounds spanning from clean-ish with some hair to moderately overdriven tones. All of this were done in my home studio using one SM57 in front of a Scumback M75 loaded in a Port City cabinet.
Now, most of the profiles were ok, and I'm using a couple of them on a daily basis. One of the profiles however, a distorted Marshall sound, behaves strangely. I didn't notice it immediately in the studio, but when I took it live, I started noticing that there was kind of a clean sound in parallel with the distorted sound, as if part of the guitar signal bypassed the amp and went direct. The part of the sound that was distorted sounds really great, but this slight direct sound of the guitar ruins the sound.
I'd really like to know what's going on here. I suspect that something's gone wrong during the profiling process, but what?
Also, are there tweaks to do after to remedy this? The direct parameter in the amp stack, the only relevant parameter I can think of, is at zero.