I created a little project that explains how to setup a audio receiver box using a Raspberry Pi which allows to stream audio from

  1. PulseAudio clients on the network or/and
  2. a Bluetooth device (e.g. smartphone) via A2DP protocol

to your stereo hi-fi system.

Raspberry Pi 3 + HifiBerry DAC+ Lite

For the full documentation and code, see the corresponding project on GitHub.