demo Bluetooth amplifier & receiver (signal), cheep, for passive Speaker, just board, XY-502B
Channel: Maximus OpimusZUZU_inactiv_
Date: 2018-05-15

TPA3116 50Wx2
Bluetooth Receiver & Amplifier from China (6,50€ on ebay).
With aux-in (Line in) for external old external devices (without bluetooth)
For passive loudspeaker.

Printed on board: "XY-502B"
Bluetooth DeviceName: "XY_BT"

Alarm Sound while clicking Volume+ to max-volume
Saving last Volume Settings (only a shot tested; ?but long term?)
Default at Startup: 1) Line-in, otherwise: Bluetooth
Plug in Line-In: Auto change to this device
Announcement are loud. Depending on your Volume Settings; but noticeable louder than music (a bit too loud).
Reason: The Volume at Bluetooth device (e.g. Smartphone) is possible not to max:
  "The Bluetooth Device is ready to pair" and
  "The Bluetooth Device as connected does successfully".
Change from Line-In to Bluetooth Mode must be possible manually (pressing switch; or unplug Line-In) 

Video-licence: Public Domain, CC-0