Presonus Digimax

Hooking up Preamps to Digidesign 003 Rack?

I have Pro Tools LE with a 003 rack, hooked to that via optical cable is a PreSonus Digimax FS 8 Channel Preamp. I have noticed that there are no more Optical outputs left for another preamp. My question is:How do I add another preamp to my 003 [...]