Digital cables have poor metals since signal travels only on the surface at high frequencies. Usually it is plain low grade copper silver plated. Also the best dielectric you'll probably find is polyethylene. Everything is neglected since characteristic impedance is the most important factor (signal reflects on impedance boundaries). If digital cable is just a coax it has shield as a ground carrier (grounded on both ends) - bad with audio signals. Of course theory and practice are two different things.
