Low Audio: difference in volume between "audio source" and speakers.

XPS 15 7590

So, after trying everything in the book, reinstalling all relevant drivers, there is no change.

Master Volume, 100. both in the system and device manager.

Sound out, either speakers or headphones, is too low, and indeed shows lower in the volume mixer than the source. I've tried music (MaxxPro helps a little), video, even system sounds from audio devices. It all suffers from the same issue. Its as if half of the amplitude is being "diverted" somewhere.

Thanks!