Equinox TOSLINK Cable

At some point in the development of the Equatorial Audio optical cable range, we asked ourselves a question that no manufacturer in the history of consumer audio has asked: what is the theoretical maximum EMI rejection achievable around an optical fiber, and can we reach it? The answer to the first part is constrained by physics — by the permeability of the shielding materials, the completeness of coverage, and the frequency range over which rejection must be maintained. The answer to the second part is the Equinox TOSLINK Cable.

Four concentric shielding layers surround the surgical-grade PMMA fiber core. The innermost layer is a single-crystal silver braid at 99% coverage — silver was selected for its superior conductivity compared to copper, providing lower impedance to induced shield currents and therefore more effective absorption of incident EMI. The second layer is cryo-treated mu-metal foil, cooled to minus 196 degrees Celsius during manufacture to permanently align its crystalline domain structure for maximum magnetic permeability. Mu-metal provides the highest magnetic shielding effectiveness of any commercially available alloy, and the cryo treatment extends its performance into frequency ranges where untreated mu-metal begins to lose effectiveness. The third layer is aluminum-mylar tape for broadband electric field rejection. The fourth layer is an OFC drain that provides a low-impedance path for any residual shield currents to reach ground without circulating through the inner shielding layers.

The combined result is greater than 160dB of EMI rejection from DC to 6GHz. At this level of isolation, the evanescent field at the core-cladding boundary of the optical fiber exists in what is, for all practical electromagnetic purposes, a vacuum. No external source — not a WiFi router, not a switching power supply, not a nearby power cable, not the Earth’s own magnetic field — can perturb it. The light inside this cable travels in electromagnetic silence.

The rhodium-plated TOSLINK ferrule connectors extend the reference-grade philosophy through the connector interface. Rhodium provides harder contact surfaces, lower insertion loss, and greater resistance to the oxidation that degrades optical coupling over time. Each Equinox TOSLINK Cable is individually serial-numbered and ships with a shielding effectiveness certificate that includes a full spectral analysis of the measured EMI rejection across the DC-to-6GHz range — because at this price point, you deserve proof, not promises.