[ubuntu] External (USB) soundcard stops working after fresh installation and restart

Welcome. Your install is fine. It has nothing to do with your issue so install, if it works fine stay with it so we can try and troubleshoot what's happening. There may be a LOT of stuff in Ubuntu Studio that you will never use, so try that and Ubuntu in a live session to see which you like best before installing. You can install anything from Ubuntu Studio in Ubuntu later if you like.

Ubuntu Studio uses the xfce4 desktop environment. Ubuntu uses Unity. If you'd rather use the xfce4 desktop, install Xubuntu (more lightweight) and same applies. You can install what you like from Ubuntu Studio later.

Is it a self-powered exteal card? This is a matter of tweaking the OS rather than reinstalling to the same issue.

(PS: If your install is fine (please confirm), and if you don't mind, I might move the thread to Hardware as it is about your hardware rather than install and you will get better support there.)