what type of receiver are you using? Does it have full dolby digital version 2 (At least) support? I have old style eqipment with the 1st version of dolby digital that had 3 speakers. (FR, FL, and R) So I run it in analog with 2 seperate jacks. (When I get my audigy 2 ZS it will be 3 seperate jacks though

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Try running it in analog.