TOSLINK ADAT cables can be relatively fragile because of glass within the cable. They are optical cables, using light to carry the digital audio signal. Each end of the cable typically comes with a small plastic cover; you need to remove this to fit the cable properly into the ADAT ports on your interface.

When you remove this cover, you will see a very small glass lens. This lens connects with another small lens inside the ADAT port, creating a tight fit so that light can pass. You will see a red light emanating from the ADAT output ports on your unit, or from the cable itself when it is sending a 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 needed to ensure a secure connection.

The ADAT connector is shaped differently at the top and bottom, so make sure the cable is the correct way up to allow it to fit into the port correctly.

Any small bends or kinks in the cable can potentially break the glass inside the cable and cause it to not pass the audio stream properly as well, so it is important that the cable is treated with care — check for damage if you are having issues with the ADAT connection, like glitching audio or loss of sync between devices.