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Reference Digital Audio 40, the new standard for digital coaxial S/PDIF signals.

Reference Digital Audio 40 utilises a carefully engineered geometry to achieve the precise characteristic impedance required for the maximum transfer of S/PDIF signals. Silver plated conductors deliver a low resistance path for high frequencies and QED "Digiloc" plugs more closely match the cable's characteristic  impedance, reducing return loss by up to 1dB when compared to conventional RCA plugs. This ensures optimal signal transfer and improved micro-timing of the audio signal.

Length 0.6m 1.0m 3.0m


Just Listen

Silver plated signal carriers, effective high quality shielding and impedance matched cordage and plugs all combine to create audible sonic improvements when compared to the competition

Triple Layer Electromagnetic Shielding

Through the use of factory controlled geometry and low permittivity foamed polyethylene dielectrics, Reference Digital Audio 40 maintains the correct characteristic impedance to match the transmission line between digital source and sink precisely. This makes for a very low jitter signal transfer which, listening tests have shown, leads to clearly audible sonic improvements.

75 Ohm Impedance matched DigilocTM RCA plugs

Domestic S/PDIF interfaces use the traditional RCA phono connector which is not impedance matched to the 75 Ohm transmission line. This causes measurable insertion loss and an increase in jitter due to signal reflections at the connector boundaries. The all new Digiloc RCA plugs are more closely impedance matched than ever before and measurements have shown, reduce insertion loss by up to 1.2 dB compared to ordinary RCA plugs.

Triple Layer Electromagnetic Shielding

A dual layer closely woven 99.999% OFC shield braid and aluminium mylar wrap with 100% coverage comprise a triple layer electromagnetic shield coaxially spaced around the central signal carrier within a foamed polyethylene dielectric. This ensures that interference signals induced by nearby high current noise sources do not contribute to higher signal jitter than would otherwise be the case. By the same token the shielding prevents unwanted voltage induced interference escaping the cable which might affect nearby analogue signal carriers.


Silver Plated 99.999% Oxygen Free Copper central conductor

Extruded foamed Polyethylene (PE) dielectric - for sonic purity and low return loss

Double 99.999% OFC braid plus Al/Mylar wrap for 100% electromagnetic screening coverage

Twin leaf 24c Gold plated QED ‘Digiloc™’ RCA plugs featuring high purity copper contacts, hollow centre pin and low eddy current design

75 ohm coaxial design with closely matched locking plug for reduced return loss

QED Lifetime Guarantee



CD player

Blu-Ray player

other S/PDIF device output



Digital Pre-Amp

AV Amplifier

other S/PDIF device input


Ultra Low Jitter

Jitter is the undesired deviation from true periodicity of an assumed periodic signal in electronics and telecommunications, often in relation to a reference clock source. A cable displaying ultra low jitter has been measured at
typically 30ps.