Apparently the stock Galaxy Tab 2 doesn't have a native USB audio feature:
A list of stock Android-powered devices reportedly interworking with standard USB DAC:
stock Android device > digital USB audio out >> standard USB DAC >> amp >> headphones
The Galaxy Tab 2 using the USB Audio Player PRO (UAPP) app could output a digital USB audio stream to a compatible USB DAC via an OTG adapter cable:
Galaxy Tab 2 > USB audio out >> OTG adapter cable + regular USB cable provided by the USB DAC maker >> USB DAC >> amp >> headphones
There is a free trial version of UAPP available on Google Play store.