My GG has run in for 3-4 days now.
Finally had the time to change the coupling capacitor to the 1uf you gave me to try out.
Personal perception : less bass and a bit more treble. Guess not transparent enough, but better than before. Not enough 3D. Maybe need more time to run in. But warmer than my previous solid state alone.
Wired the case (and therefore shell of chokes) to earth (main power supply). Result : ddddddddddddddddd... sound problem solved. Now only hum sound problem requires attention.
Will change the 0.1uf to the new ones I bought and listen again.
I think with Auricaps will improve a lot.
Will also try Derik's suggestion. Expect an even better sound.