Currently Spotify defaults to using the default sound device under windows when launched, it would be neat if you could choose which sound device you want to use isntead in the options screen,
I think I opened a support ticket for this feature about a year ago. Back in the "spotify:config2" days. Got an answer somewhere in the realm of "not supported".
I really need this feature. I use multiple soundcards to split outputs into different sets. For example. I do not want Spotify to playback using my headphones but my speakers while I play a game or anything else for that matter. I also tend to Stream some of my games and don't want Spotify to be recorded- This is the whole reason I had to set up another soundcard by the way.
Please, just add this small but essencial feature like any other Audio related product.
Updated on 2020-01-10
Hi folks.
Windows 10 now lets you set the default output device on a per-app basis.
@Sebasty posted a great explanation here.