High-speed digital transmission is very different from audio frequency signal transmission and requires a different knowledge base and design criteria. Audio cable signal transmission is governed by the principles of inductance, capacitance, and resistance. By contrast, high-speed digital signals are governed by a principle known as ‘transmission line theory’.
The performance of a transmission line is governed by the characteristic impedance of the cable. Certain types of cable require a specific characteristic impedance to achieve optimal performance — for instance, cable TV coaxial cables are 75 ohms, while test equipment cables require 50 ohm cables. Modern audio and entertainment systems may have multiple digital connections, each with potentially different characteristic impedances.
While the characteristic impedance is a critical factor in the optimal performance of digital cables, our research also indicates that the precision with which a digital cable is constructed has a significant impact on its performance.
Superficially, digital cables may look the same as analog cables. For example, a S/PDIF cable can be terminated with RCA connectors, much like analog interconnects. Because the terminations appear the same, analog interconnects could be used as a substitute for a digital cable; but since it has not been designed with the correct characteristic impedance, the performance will suffer.
Cable: Ohno VTX™ twisted pair, FEP dielectric, braided shielding
Termination: Shunyata Research XLR connectors