Yea the one I had was a 2 Channel H, which I really liked. I brought it back to GC for repair. Got it back, and played it in the store for 30 minutes. Dead quiet. Took it home and it sounded like I plugged a vacuum cleaner into it instead of a guitar.
Yep had a hot rodded M from a limited run for a dealership in Canada... sounded amazing but same thing you describe. Same with the other amps.