If you use the "Y"cable to connect both A & B from the ADAT Bridge (or any 2 8ch Interfaces) to the d24, you will save on DSP mixing power, since the d24 card has the ability to mix 16 channels of I/O using its on-board DSP chip.Assigning a peripheral on a DSP Farm takes 6 channels on that Farms first DSP chip, so that chip can then only be used for Mixing.