Initial impressions...
Settings... Under 'Sound & Notifications'/Advanced', the area for activating the DAC is grayed out... HMM... can't turn it on...thinking maybe once the music app is being used it automatically activates the DAC.
The DAC will only initiate with a line in, like headphones or external amp. Get that app I listed as it will enable the DAC on most, if not all, apps when using headphones or speakers. Enjoy the phone!