Ok, i have found why ADPCM was dead.
IC503 was not grounding on pin 4. While looking closer, via near pin 5 of IC503 was corroded, that's why IC503 was not working.
So i put an electrical cable into the via and soldered each side of the pcb. It' s not pretty to see but it works. By the way, this stuff solved my main audio problem, i can now desolder Slipty's trick !
All audio problems were ground related, at least for me.
Thanks to the guy for these two diagram, I found them on this wonderful forum :
They are very useful !
After that, I took a second look to other vias, next to the cd side of the Duo. I had to repair 2 others the same way.
CD works 100% now, just fine !
I'm waiting now for a RGB mod, and i have to 3d print an Hucard door cover too ! Mine was missing.
Thank you everybody for all your advices.