I am using 2 MOTU 896HDs. the second unit is connected to the first via ADAT. I have become aware that the ADAT output of the second MOTU 896HD unit is reduced 3dBFS compared to that same unit's analog input metering.
In the example illustrated below the analog inputs of both units were fed matching signals. The results recorded in Cakewalk's SONAR show a -3dBFS drop for the signal routed thru ADAT.
I have also noted that the ADAT bus has a small time gap... 7 samples as illustrated below.:
I simultaneously ran two mono 1kHz test tones generated on a Shure FP33 portable mixer at +4dBu line level into the channel 1 XLR inputs on each of the two MOTU 896HD boxes. The inputs were set at +4dBU which disengages the front trim knobs. The input of #2 MOTU 896HD was routed to #1 MOTU 896HD via ADAT.