Agree with Darryl. The single make or break thing is clocking. Do it wrong and one of two things will happen; all the ADAT inputs will click and pop when in record, or, none of the ADAT inputs will work at all. Go to Setup>Hardware(in Pro Tools) and set the Clock Source to ADAT or Optical and make certain the sample rate of the external device(Audient ASP880 or whatever it is) matches the sample rate of your session(forgetting this can open a whole can of worms
). In the case of Mbox Studio, the clock source is set in the Mbox Control software by clicking the little gear in the upper right corner. BTW, this is also where you select ADAT or SPDIF for the optical IO
