Optical to digital coax converter

Hi everyone,
I just purchased optical to digital coax converter, so I can play Sirius XM
radio through my audio gear.This unit is connected to dish sat. I do not
have a digital coax at the moment, so I tried using interconnect cable instead. When I turn everything on, all I hear is high frequency clicking
from the speakers. What could be the problem? Are the cables the culprit or something else?
I should mention that indicator light comes on, telling me that the
signal is locked in. If any of you have any idea , I would appreciate
hearing from you.
I thank you ahead for your response.
Regards,
Rod