I have two FirePower FC610 interfaces. One is used exclusively by Kyma/Pacarana (connected to Mac using Sonnet firewire hub shared by Pacarana), the other exclusively by software running on my studio Mac, (connected to Thunderbolt on the Mac). The interfaces are connected to each other via optical cables -- both in and out. The interfaces both have a steady glowing light indicating that they both believe optical connections are working. I know have successfully used them with audio going *from* Kyma/Pacarana *to* software in my Mac. This may well be the first time I have tried to have both devices using optical ins and outs simultaneously in a sound-quality critical environment. I am getting glitches that sound like a clock/sync problem and am having trouble figuring out the best combination of settings to use. (Perhaps it's not possible without a master clock?)
Kyma has 3 choices: Internal, SPDIF Input, and Syt match (I have no idea what this last one does other than cause "Silent Device" to show up for Audio Input and Audio Output).
Mac audio software has four choices: Internal, Device Internal Clock, SPDIF Input. and Mac.
Any suggestions as to the best choice of setting to use?