No signal when connecting interfaces via ADAT optical cable

I have 2 Behringer UMC1820 interfaces. Setup is as follows:

MacOS<—USB—>UMC1820 #1<—optical—>UMC1820 #2 (with ADAT selected)

I see one device show up in my Mac with the correct total aggregate of 20 inputs, 8 in + 2 SPDIF, 8 ADAT + 2 SPDIF. In Ardour, I also see the single device with all 20 inputs. Problem is, if I assign one of the ADAT inputs to a track in Ardour, it has no signal. Session 48kHz, so I should be able to get all 8 ADAT inputs at that rate.

I have been able to get this to work by connecting both USB and creating an aggregate device and using Jack, but shouldn’t this all work over the optical cable method?

Thanks!

How do you set the second UMC1820 to route one of the analog inputs to an ADAT output instead of to USB? Wouldn’t the ADAT outputs from the second UMC1820 normally be assigned to a USB output by default?

There was nothing to set. Once you connect the UMC1820 #2 Optical Output to UMC1820 #1 Optical input, it automatically routes over optical and the Mac recognizes everything via the UMC1820 #1 USB connection.

I thought your complaint was that you could get no signal from the ADAT channels, which would imply that it is not automatically routing the inputs to optical. I stand by my original conjecture, the ADAT channels from interface #2 are fed from the USB interface, not the analog inputs, and the analog inputs are routed to the USB interface, not the ADAT interface. I’m not sure how you would validate or disprove that conjecture, because there does not seem to be a user manual available for that interface, only a quick start guide which gives minimal information.

All your computer can see is how many channels are available on interface #1, because that is the only direct connection it has. The question is how to verify the routing between analog channels, ADAT channels, and USB channels on interface #2.

Yeah looks like I cannot string 2 UMC1820 devices together via optical afterall. Need something like the ADA8200 for that.

Aggregate device works, guess i’ll stick with that.