If the mdac works on USB, then when you change to out put to your 2704 da you will have to reset the audio output.
If you click on the red more then you will see the info.
A reboot will be required.
It has always been thereRaspbian Stretch with desktop
Image with desktop based on Debian Stretch
Version: April 2019
Release date: 2019-04-08
Kernel version: 4.14
Release notes: Link