I have two firestudio projects and a firestudio tube, with a Mac Pro tower, they all work and I fallowed the rules to cascade the units, my issue is because of the firestudio tube does nor have SPdif for the transfer of digital audio from the master unit to the slave units I can not get audio to the firestudio tube, is there a way to correct this? the projects work fine and send & recieves audio the tube seems to work independently of the projects! but yet Presonus says its possible to connect this unit together??