I'm having a similar problem.
I'm trying to mic up my Marshallo Master Lead Combo (solid state form early 80s), distortion from
my zoom 3030, with an SM 57 and an AKG C3000.
The sound that I hear from the amp is OK (not brilliant - it's an aging solid state amp), but when I play back what I've recorded, it all sounds, well, a bit weedy.
I'm placing the 57 about 2ins from the grill, and its point at a slight angle at a point around an inch from the cone (I've tried other position, but this has been consistently the best of a bad bunch). The C3000 I've tried everywhere - rear of the cab, other speaker, in line with the 57 only a coupla feet away, and also about 6ft away (which _really_ sounds weak). Can't really get a sound I'm happy with.
Am I searching for something unattainable? I dunno, but any further tips would be appreciated.
Ta,
matt