I assume you're using Pro Tools LE? Have you considered switching to Pro Tools M-Powered?
That could be used with one of the compatible PCI interfaces which would provide better
latency than a FireWire or USB device.
OK, I just re-read your post and see
you mention using Cubase
which case, swapping your Mbox for any cheap PCI/PCIe interface with S/PDIF would give you
Edited by alzilla (16/12/11 04:07 PM)