Windows volume or AMP?

[PedsRN]

Most likely this is a silly help question so I apologize in advance, but I don't really no the answer nor have I found it..
 
Am I suppose to have the volume in windows/realtek hd manager at 100%? Then what do I set Spotify for example? I have a fii0 amp with th900 mk2's and akg q701 as well. I'm confused as to what I set the amp to then windows then the audio player of what im playing.

 

[Dulalala]

Set Spotify and Windows volume at 75%-100% and control volume with your amp.

 

[fakemeta]

If you can control the volume through the amp, theoretically you should set the volume to 100% in your application and also in windows sound settings.