Volume goes down when I switch from iOS mobile back to desktop

[vivehenriv]

When I open Spotify on desktop on Windows 7, the sound quality and volume is great. The slider in the bottom right only needs to be about a third of the way to get good volume (with my system volume turned to a good level for other things such as YouTube). But when I go off and play music on my phone and come home after a long day, the same volume settings produce a much lower volume. If I close and reopen Spotify, it comes back to giving me good volume at the original settings. Any ideas?