Derived from the German version: Go to View >> Options >> Internal Filter >> Audio-Switcher. Check the following boxes:
- Enable built-in audio switcher filter (requires restart)
- Enable custom channel mapping
Mark all speakers on all channels (if you want to mix them up) or choose your dominant input channel. Don't forget to switch off normalization, which is set to 400% by default.
See screenshot below, just make sure all boxes checked in it are checked on yours.
