What is your source, and what is it set at?

When I use my setup I have windows set to 100% (Spotify at 90 since tracks can vary in volume) then I control all of my volume from my amp/dac. Before that I noticed distortion in my headphones and it was because I was sending a quiet signal (windows at like 30) and then amplifying the signal a lot more with the amp and that was what led to my distortion issues.