Many customers who have not used ADAT cables before can make small mistakes that end up damaging their unit or affecting their audio, so please read this guide if you are unfamiliar with the use of TOSlink ADAT Cables.
TOSlink ADAT Cables are very fragile, as they are made of glass within the cable. They pass light which carries a digital audio signal. Thus each end of the cable has a small plastic cover, which looks like a small bubble, which needs to be removed in order to fit the cable properly into the port.
When you remove this cover you will see a very tiny flat glass lens. This lens meets up inside the ADAT Port with another small lens creating a tight fit so that light can pass. You will see a Red Light emanating from the ADAT Out Ports on your unit, or from the cable itself when it is sending signal.
Once the plastic cover is removed the cable should seat in the port easily. Forcing the cable unnecessarily can damage the ADAT Port Doors, which are important to keeping the cable secure.
Also be mindful of proper vertical alignment of the connector, as you will see the ADAT Port and Connector have small bevels so that they only fit one way.
Not only should you remove the plastic cover but please be careful to keep these if you ever want to remove the cable and store it.
You will want to protect the cable at all times as scratches to this lens can damage the cable and your audio stream.
Additionally any small bends or kinks in the cable can potentially break the glass inside the cable and cause it to not pass audio stream properly.
If you are having any issues with your audio stream you should first check that your units are properly Synced. This means that one unit is receiving clock data from the other unit. If both units are set to "Internal" you can get digital jitter, or crackly audio.
However if you are confident that your units are in sync, or they are unable to receive sync from each other, you should check a new ADAT cable, as often cables can be damaged beyond repair yet appear completely fine, due to an accidental bend or scratch.
If you do have questions about digital jitter or syncing your units please Contact Support.