I finally found a not that expensive path :
Rca audio switch: 4 rca input to one rca output for consummer audio.
price range : 9 to 40 euro.
Active direct box: start price: 33 euros
Monitor volume control : start price 28 euros
can be replaced by something like a Presonus Central Station Plus
or other devices, if needed by people who need things like this.
of course audio cables,
and finally a power amp class D.
About the audio rca switch it found it inside an informatic shop.
I found at hifi shops A/B listening switch and it's very expensive.
I begin to understand how audio thing is working, it can be very interesting.
Here i share the little search i did on my own.
edit: just saw a class G amp (apart champ-2 ) and it's exactly what i needed.
Have a good day everybody
