[BScout]

I may not be able to follow along but you can't use an HD i/o as an extension of the MTRX for talkback. The monitoring functions of the MTRX (DADman/ProMon) exist only in the MTRX. The HD i/o is not active when Pro Tools is off. If the HD i/o is routed within Pro Tools from an input coming from the MTRX to the HD i/o (MTRX PT output > HD i/o output), you could use it. But you have to have an actual channel setup in the Pro Tools session. This is because the HD i/o does not operate stand alone and can't be communicated to directly without Pro Tools in-between.

However, for clocking, don't use "loop sync". Set the MTRX to Pri/Pri. On the MTRX, set sample rate to "internal" and set Adapt to "ProTools1." Then run a word clock cable from the wordclock output of the MTRX to the word clock input of the HD i/o. Then in your session setup of Pro Tools, flip the sync on the HD i/o to word clock. Then set your MTRX to internal from session setup.

Then your system will change word clock with whatever session you open (both the MTRX and HD i/o.)