Emu XL-7 & MP-7 User's Group

Hi all

Wanted to try out the SPDIF connection on my MP7, so I took an RCA 
cable and hooked it up to my SBlive sound card. 

It works, but I get crackles, pops and breakups, even adjusting the 
volume down.

What am I doing wrong?
Do I need a special RCA cable?
Is there a setting on the MP7 itself?

TimC