So to start off I'll say that there's tons of information on the internet but an insane amount of it is contradicting and often times confusing. After googling for a few days I have the general idea of why and how things work, but I still got some details that I need to iron out.
Firstly, what does volume really depend on? I know it depends on sensitivity, but why do my HD 201s sound at least 5 times more silent on my Samsung galaxy mini than my Xonar DG card? Is it just because of voltage output being way lower on my phone or are there other factors as well? Oh, and what's the voltage output of for example Xonar DG card or an onboard card?
Secondly, how exactly does gain work? Does increasing gain decrease the sound quality? Also, why does for example Xonar DG audio center list the "HP Advance settings" for different ohm headsets when in reality it only increases gain?
Lastly, some headphone specifications list "maximum input power". What exactly does that mean? Is my sound card always capping the xxxx mW limit or is it some limit on how much gain you can get from an amp?
I know that's a lot of questions, but hopefully someone can answer. Thank you in advance.