Such a converter would have to act as a USB "host," which likely means that it would have to either be a computer that could accept a S/PDIF input or a device designed to emulate such a computer. And as far as I am aware any such device would probably cost a good deal more than the kind of simple converter you appear to be looking for.
Converting in the opposite direction (USB to S/PDIF, using a device connected to the USB port of a computer) is technically a much simpler task, and many devices which can do that are available at relatively low cost. But converting S/PDIF to USB is a different story altogether.
Good luck. Regards,
-- Al
Converting in the opposite direction (USB to S/PDIF, using a device connected to the USB port of a computer) is technically a much simpler task, and many devices which can do that are available at relatively low cost. But converting S/PDIF to USB is a different story altogether.
Good luck. Regards,
-- Al