DAC's output voltage managment on Arduino Due

David_ZI:
I need both DAC's on Due to be able to output a voltage from 0- max 4 Volts. Is there a chance that the Due will do it without any additional /and or support circuitry= David

No, see this tutorial:

David_ZI:
is the Due capable of using both onboard DAC'S simultaneously=?

Yes, select both channels and Word transfer in DACC_MR with the appropriate channel setting (bits 12 and 28).