I've found a Pioneer M-J310 amplifier.
This amplifier it's a 90's stackable hifi vintage. It's a 50W+50W on 8ohm output. In class AB.
The problem with this amplifier is that it comes alone without the preamplifier and the other stack elements, and it comes with a custom plug.
So, in order to make this device work I've to find the schematic online and check which is the correct wiring to makes this amplifier goes out from stand-by.
After having found this trick I've tested it with an aux cable. It works good, not the best thing I've heard but clean.
So I decide to add a toggle switch on the input to select between an RCA stereo input plug that I've added and a bluetooth input.
To power the bluetooth board I've take the 15V voltage output from the board into a stepdown converter, to build 5V out of it. Then to decouple the signal I've added a small 1W DC to DC converter. This last one component is really important if you want to keep your bluetooth audio out clean.
I've also added a volume control by using a simple stereo potentiometer.
Notes
- read risk disclaimer
- excuse my bad english