Digital data transfer is characterized by peculiar problems that require a different approach with respect to analog data transmission.
For instance, S/PDIF or AES/EBU connections between CD drive and its D/A converter transfer binary data packages (i.e. square waves that are rather different with respect to sinusoidal waves).
That suggests the cable could not influence appreciably the overall quality of transferred data because spurious capacitance can not attenuate the signal.
This is in principle true, but… the square wave passing trough the digital cable may affect the jitter.
Therefore, the signals’ temporal lag delay will affect the phase.
For this reason, also in this case one has to consider the signal celerity, dielectric property and spurious capacitance thus influencing the cable’s geometry, the conductor type, the dielectric medium. The final results will be a cable with suitable impedance (75 Ohm for S/PDIF – 110 Ohm for AES/EBU), signal propagation speed greater than 85%, capacitance lower than 50 pF/m.