Apogee AMBus HD, User Manual, Page: 12 / 24

APOGEE ELECTRONICS
4
AMBus HD card – User’s Guide
Incorporating a SYNC I/O
There are 3 configuration possibilities for incorporating a SYNC I/O into the HD system :
using a Master Clock, SYNC I/O as master, and HD-equipped Apogee interface as
master.
Using a Master Clock – Once again, the use of a Master Clock such as Big Ben greatly
simplifies clock configuration. Simply connect one of Big Ben’s outputs to a SYNC I/O
clock input, and set the SYNC I/O’s clock source to the appropriate setting. Be sure to set
the Big Ben’s sample rate to correspond to the sample rate of the Pro Tools session.
SYNC I/O as master – In certain situations (for example, when locking Pro Tools to time
code from an analog tape machine), the SYNC I/O must be the clock master. In this case,
we highly recommend inserting a Big Ben Master Clock between the SYNC I/O’s word
clock output and the word clock inputs of the audio interfaces for jitter
attenuation.
HD-equipped Apogee interface as master, SYNC I/O slave – Due to automatic switch-
ing of clock sources in Pro Tools, it is not practical to lock one of the connected audio
interfaces internally while the SYNC I/O is locked to word clock. It IS possible, by using
the SYNC I/O’s Loop Sync In and setting the Apogee interface’s Word Clock Ratio setting
so the sample rate of the interface is at the desired setting while the clock system runs at
a 44.1/48k multiple.
Clock Configuration
(when incorporating Digidesign or Prism HD Interfaces)
Again, making clock connections when incorporating a Digidesign or Prism interface is
simplified by using a Master Clock, so direct connections may be made between the
Master Clock and each interface.
We know, we’re starting to repeat ourselves, but that’s how useful a Master Clock is.
If a Master Clock is not employed, keep in mind that the word clock input of Digidesign
interfaces is internally terminated; thus it’s not possible to employ BNC “T”s to distribute
clock.