Can I use my PC as an audio device for my Android phone?
A good app for this is BubbleUPnP for DLNA/Chromecast

Unlike other media server apps, it supports a lot of devices:


Chromecast, Chromecast Audio, Nexus Player, Nvidia Shield, and other Google 
Cast devices
DLNA TVs and music receivers from popular TV and HiFi brands
Xbox 360 and One, Playstation 3 and 4(**)
Amazon Fire TV and Fire TV Stick
local Android playback


It possess both media servering and rendering functionalies so your audio will be pushed to the playback DLNA device e.g TV and can do vice versa. 

Unfortunately you'll need root to enable Audio Cast, and the popular Xposed Framework tool BubbleUPnP (Audio Cast)  as well. You don't need to download an extra module - the Xposed module for Audio Cast is included in the standard BubbleUPnP app. 

Credits


BubbleUPnP