Spotify - Cambridge Azur 851N

Can someone explain this to me?
when I stream Spotify from my MacBook and choose the 851N from the sound (speakers) icon on my computer toolbar the sound volume and quality is less than if I select  the little speaker icons in the Spotify app. There is considerable sound improvement when I select the tiny speakers  icon from Spotify. Just wondering why the difference.

The volume on your computer is the "master control" for the network player. Set that first.

For more control over the level, use the spotify app. If you get it just right the level will remain optimal. Are you saying the spotify app has a superior digital volume control? Sound quality would be determined by the file itself and the chips inside the unit you’re using.

Volume too high - hearing loss, problems with resolving complex music
Volume too low - missing out on important nuances and other details