The QED Reference SR75 is a high-performance digital coaxial cable from QED’s Reference range, designed for S/PDIF connections between CD players, DACs, and digital preamplifiers. It uses a precision-engineered 75-ohm coaxial geometry to ensure accurate impedance matching — critical for minimising signal reflections and timing errors (jitter) in digital audio transmission.
Construction
At the core of the SR75 is a silver plated 99.999% oxygen-free copper (OFC) conductor, stranded for improved flexibility. The silver plating raises surface conductivity, which benefits the high-frequency signal components that carry digital audio data. Surrounding the conductor is a foamed low-density polyethylene (LDPE) dielectric, chosen for its low loss characteristics at the frequencies used by S/PDIF.
Shielding uses a triple-layer arrangement: an aluminium/Mylar foil wrap combined with dual 99.999% OFC copper braids. This construction provides comprehensive electromagnetic and radio-frequency interference rejection, preserving signal integrity in electrically noisy environments.
Termination
The cable is fitted with QED’s Reference phono plug, featuring an 8-leaf 24K gold plated RCA ground ring with a split centre pin and locking mechanism. The multi-leaf ground ring ensures a consistent, low-resistance contact across the full circumference of the socket, while the split centre pin adapts to variations in socket dimensions for a secure fit.
| Cable Type | Digital coaxial (S/PDIF) |
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| Impedance | 75 ohms |
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| Conductor | Silver plated 99.999% OFC, stranded |
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| Dielectric | Foamed low-density polyethylene (LDPE) |
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| Screening | Triple: aluminium/Mylar foil + dual 99.999% OFC copper braids |
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| Connector | RCA (phono) |
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| Plug | QED Reference — 8-leaf 24K gold plated ground ring, split centre pin, locking mechanism |
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