I thought you got your issue with the headphone output and the SPDIF connection between your Eleven Rack and the Mbox3 or Saffire interface sorted out in
the other thread here . Are you look for another solution?
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Obsidian Dragon
MacbookPro14,3 - Intel Core i7 3.1 GHz, 16 GB
MacOS 13.6.6 running Protools 2024.3.1
Mac Studio M1Max - 64GB
MacOS 14.4.1 running Protools 2024.3.1