I just picked up the Logitech Z-5500's and am super pleased with them.

I got the Xbox 360 going to them with Optical and am TRYING to use the Coaxial on my HD Settop.

Question is, is Coaxial digital? I'm highly assuming that it is, but just want to be sure.

Also, my sound keeps cutting in and out while using the Coaxial with my HD box, which is why I asked my first question.

Thanks.

Coaxial does carry a digital signal. If you are having problems with your HD box, try using another cable and see if that is the issue. You can use a yellow composite video cable to test and see if it is in fact a problem with your current cable.