hmm, I will sift through some old threads and find the links brb :P
heres this one
AMPS: How do they work. this was about the best one I could find.
Simply put they shift your find size by how big the amp is. Natural claim of IV found with 103 amp = VII find. Amps help find rare materials, example, a claim worth enough to be an IV might only be 1 unrefined piece of it. If its there and you dont have an amp to bring the natural size up to the value of one piece, you just wont find it.
Heres another interesting one,
Punished for having an amp