Tributaries - CABLE-4D - Bulk Video Cable (100m) The Series 4 begin with ultra-pure highly conductive oxygen-free copper (HC-OFC) developed specifically for digital audio applications. To maintain a consistent 75-Ohm impedance, the coaxial Series 4 cable’s 22AWG center conductor is surrounded by a perfectly concentric layer of foamed PE dielectric. Dual shielding blocks noise from entering the signal path. Tributaries Series 4 precision 75-Ohm engineering provides accurate digital audio performance.