Just wrote this in reply to a comment linking to some of oratory1990’s thoughts on amps. I am linking here so OP can see.

Amps generally are reducing voltage for headphones from line level (since they are mostly very sensitive or efficient) - the amp is outputting less voltage than it receives but is increasing current to be able move and control the physical driver membrane via the alternating electrical signal applied to a dynamic driver’s coil and magnet system. Same goes for most types of drivers, with various quirks.

https://www.reddit.com/r/headphones/comments/z5wwmn/comment/ixzbgik/