Mac Pro to Lexicon MC1 - Optical Audio

Needs some help!

I am trying to hook up my Mac Pro G5 to my Lexicon MC1 using Toslink Optical, not sure of the missing link!

Mac Pro: Sound output set to Digital Out, Toslink Cable connected to Optical Out running iTunes.

Lexicon MC1: Toslink attached to Optical input 2 (I've tried all three inputs) and now I'm stuck! I am unable to locate what my next steps are???

The line out and internal speakers work fine on the mac, the Lexicon works fine with the rest of the theater setup?

Must be something simple!

Thanks in advance for any help!

Robert

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Mac Pro, Alesis iO26, Lexicon MC1, Lexicon 512, Hafler Trans.Nova P7000 Diablo, Sony Blueray, B&W Speakers, Optoma EP 758