[Wyllys]

Another possibility is that at home you are in a different relationship with the amp than when playing through a PA at the open mic. HF waves are shorter and more easily focused, so that part of the sound will be less present when the playing position is to the side and/or behind the speakers. Yet the LF is not diminished, the longer waves broadcasting in an ever wider pattern as you go down in frequency.

The end result is that while the tone may sound "bassier" on stage it is entirely possible for it to be fine out front but unbalanced toward the low end on stage due to the physics of how PA speakers work.

If you can, set up a PA speaker on a stand, play a good guitar CD through it and walk around the speaker from directly on axis in the front to off axis to the side all the way to behind and hear how the sound becomes muffled as you get further off axis.