When connecting external preamps to the Liquid Saffire 56 via ADAT, the biggest consideration is how all of the devices are synced together. All digital devices in a signal chain must be synced to a common clock source, in order to pass audio without any clicks, pops, or glitches. Larger and more complicated digital systems will often have a separate master clock, however this is not usually necessary in a smaller system. The most common ways to sync a Liquid Saffire 56 with 2 external preamps via ADAT without an external master clock are outlined below:
1: Syncing via Word Clock, Liquid Saffire 56 as master
In this scenario, the LS56 is synced to its internal clock, and the 2 external preamps (in this case Focusrite OctoPre MkII Dynamics) are synced via Word Clock.
Please note that if the word clock inputs on your external preamps are unterminated, you can use a T-piece to connect the second preamp via Word Clock, instead of connecting from the Word Clock Out of the first external preamp. The final device in the Word Clock chain will however need to be terminated, either internally or externally. For more information about this please consult the manufacturer of your external preamp.
2: Syncing via ADAT, Liquid Saffire 56 as master
This setup is very similar to the one above, although the Word Clock connections have been replaced by extra ADAT cables going from the outputs of the Saffire to the inputs of the external preamps. The external preamps are then syncing to the clock signal embedded within the ADAT bitstream.
3: Preamps without ADAT inputs or Word Clock outputs
When trying to sync 2 preamps to the Liquid Saffire 56, neither of which have ADAT inputs or word clock outputs (unless the word clock inputs are unterminated - see note in scenario 1 above), it is necessary to set one of the preamps as the clock master. It is then possible to sync the Saffire to the incoming ADAT bitstream from this unit, and to sync the second preamp to the Saffire via Word Clock. The Saffire can be synced to either of its 2 ADAT input ports, so it is important to ensure that the correct one is selected in the Saffire Mix Control software.