Recently aquired digital cable from Comcast, and when I saw the digital coax output on the back I thought "cool, just hook it into my external GDA-600, and away we go.

Problem is all I get is digital clicks and noise even though the GDA-600 is reporting a signal lock. Is this some incompatibility issue with the Comcast digital receiver and my trusty but old GDA-600? I've otherwise had no problem with the GDA and all other sources; computer sound card, DVD players, etc.