QED Signature Audio 40 RCA Interconnect (3m Pair)

The Signature Audio 40 sits at the top of QED's three-tier Audio 40 analogue interconnect range, above the Performance Audio 40i and Reference Audio 40. Developed to mark QED's 40th anniversary as a British cable manufacturer, the design focuses on a single engineering priority: minimising capacitance across the signal path to preserve timing and recover fine detail from a two-channel source.

Construction

The conductors are silver-plated 99.999% oxygen-free copper (SPOFC), high-purity copper with silver plating for improved high-frequency transmission. The dielectric is PTFE (Teflon), chosen for its low dielectric constant, which limits signal energy lost to cable capacitance across the audio band. Capacitance measures 63 pF/m, inductance 0.37 µH/m, and loop resistance 0.072 Ω/m.

The geometry is an asymmetrical twisted pair, which is the basis of QED's Complementary Conductor Technology. Two conductors of deliberately different diameters carry the same signal simultaneously. High-frequency components tend to favour the thinner conductor due to the skin effect, providing an alternative pathway and reducing the time-smearing that occurs when all frequencies share a single conductor.

Shielding

Electromagnetic interference is addressed in three layers. An SPOFC braid provides 100% electromagnetic coverage around the signal conductors. Inside that sits an aluminium wrap for additional broadband screening. The outer jacket is a PVC compound loaded with zinc/manganese ferrite, a material that absorbs high-frequency interference rather than reflecting it back.

Cryogenic treatment

The complete cable assembly is cryogenically treated at temperatures below −190°C. QED states that deep cryogenic treatment eliminates dislocations and fractures in the copper's micro-structure, and their listening tests consistently favour the treated cable over an otherwise identical untreated version.

Analoc2 connectors

The Analoc2 RCA plug is a QED-designed connector developed specifically for the Audio 40 range. The signal pin is hollow and rhodium-plated: the hollow construction reduces mass and addresses skin effect at high frequencies, while rhodium provides a hard, corrosion-resistant contact surface. The plug body uses high-rigidity thermoplastic rather than metal for both the inner support structure and the collar, eliminating eddy current distortions associated with metallic connector bodies. The ground connection is made via a dual-blade arrangement that increases contact area, and a locking slip ring on the barrel tightens the blades against the socket as the plug is secured, improving both ground continuity and mechanical stability.

At 3 m, this is the longest option in the Signature Audio 40 range. The three-layer shielding and low loop resistance (0.072 Ω/m) become particularly relevant at this length, where the cable is more likely to run near mains supplies or other sources of interference.