Hi Christian,
I made the followind testing with no more succes :
Connecting directly the 2 mac together through Ethernet (not cennected to internet) with a cross-over cable and once with automatic setings (DHCP / Autoselect speed) and second with manual setings (manual IP, no DNS, no Router, forced to 1000 base-T, the mode "command+K" working fine so the see eatch other...) and i steel get audio drop out !
so i wonder if any of this will change with a switch between them as the setings should be the same (exept DNS & router adress) ?
What am i doing wrong here ? i thought i underdstand all you tald me but eather something is not working for my setup or I missed something you explained to me...sorry for being so slow ;-)