In the vast majority of cases, soundmen would approach my setup wondering which one amp they should mic up, then upon hearing me ask them to put both through the PA they'd get confused. They'd do it, but most would go on to fuck something up. Here's the sort of stuff I had to deal with;
- Running one amp much louder than the other because they "preferred its sound".
- Running the two amps out of phase.
- Panning the clean/dirt amps to opposite sides of the PA.
- Doing as I requested, but explaining that because of "phase being picked up by both mics (

Occasionally we'd have a sound guy who's worth his salt and understood what was going on.
Anyone else have that kind of trouble using two amps?