Difference of guitar and headphone amp

[mkyy]

Is there any electronic geeks around to show me the difference of a guitar amp (tube) and an headphone amp?? Don't know if it's possible, but I wonder if there's anything I can modified to make my dusting guitar amp to drive a headphone.
Thanx

 

[Dusty Chalk]

Guitar amps usually distort on purpose, to emulate that great Marshall (or whatever) sound. Whereas the kind of headphone amps that we talk about here are trying to minimize distortion.