Audioquest Coffee Coaxial 1.5m

AudioQuest Coffee Coaxial: the high-end S/PDIF connection

A single RCA plug at each end, and the entire stereo stream from a CD player or a streamer reaches the DAC. The S/PDIF coaxial connection may seem insignificant; yet it is demanding, since its impedance, shielding and the radio-frequency noise it allows through determine what the converter receives. AudioQuest positions this model just below the Diamond, at the top of its silver-plated copper digital range.

One cable for both channels

Confusion is common: the plugs are those of an analog interconnect cable, but the required task is entirely different. A coaxial connection carries the complete stereo stream over a single conductor, with a characteristic impedance of 75 ohms that must be maintained over the entire length. One output socket on the source, one input on the converter, one cable: there is no need to buy two as with an analog connection.

A special feature of coaxial geometry: the shield is not merely protection, it is also the return conductor. Everything it picks up therefore ends up in the signal path, which explains the care taken in its construction.

The choice of silver plating

The conductors are solid, long-grain copper with 10% silver plating. AudioQuest’s reasoning is based on frequency: an S/PDIF signal operates in the megahertz range, and at these frequencies current flows almost exclusively along the conductor’s surface. Placing the most conductive metal on the outside therefore treats the area that matters, without paying the price of a solid silver conductor, reserved for the Diamond.

Using a solid conductor rather than stranded wire eliminates electrical and magnetic interactions between adjacent strands. The selected gauge, around 21 AWG, remains modest: this is consistent with a low-amplitude, high-frequency signal, where surface area takes precedence over copper volume.

Shielding that protects the shield

Achieving 100% coverage poses no particular difficulty; the essential part comes afterwards. Conventional shielding absorbs radio-frequency noise and then drains it to the device ground, modulating the reference ground plane on which the electronics rely to reconstruct the signal. The NDS system addresses this exact issue with five alternating layers of metal and carbon-loaded synthetics, which absorb and reflect stray energy before it reaches the layer connected to ground.

In other words, the cable does not merely block external interference: it avoids passing it on to downstream electronics. This is where AudioQuest ranges differ most clearly from one another, with the number of layers increasing according to the model level.

Permanent dielectric biasing

This is the key difference from the Carbon, positioned just below it. The insulation surrounding a conductor behaves like a parasitic filter that stores and then releases energy, with delays varying according to frequency. The DBS system applies a 72 V DC voltage to this insulation to saturate and align its molecules, linearizing the filter and improving the dissipation of induced radio-frequency noise over a wide band. The process is patented and powered by a battery pack attached to the cable, featuring a test button and an LED to check the charge status from time to time.

This voltage never passes through the signal: it polarizes the insulation, without any useful current flow. As a practical trade-off, the pack adds bulk midway along the cable, and the additional layers make the cable thicker than entry-level models. Behind a tightly fitted cabinet, it is best to plan for this before installation.

Hard foam to maintain the geometry

The insulation uses nitrogen-injected hard-cell foam. Nitrogen, like air, does not absorb energy or return it to the conductor, limiting distortion introduced by the insulation itself. The rigidity of the material serves a second, more mechanical role: it maintains the relative position of the conductors along the entire cable length, a prerequisite for stable characteristic impedance.

On a 75-ohm connection, this stability is not cosmetic. A variation in geometry creates an impedance mismatch, and therefore signal reflections liable to blur the transition edges the converter uses to recover the clock. The brand’s more affordable ranges use expanded polyethylene based on a similar principle, but less rigid.

Plugs assembled without solder

The terminations use cold welding: the contacts are assembled by compression, without filler alloy whose conductivity would be lower than that of the metals it joins. The contact consists of a silver deposit applied directly to pure red copper.

Two practical consequences. The cable is made to the ordered length and cannot be shortened afterwards: measurements should be taken before purchase, allowing a little extra for the actual routing behind the cabinet. And since the conductors are directionally oriented during manufacture, printed arrows indicate the connection direction, from the source to the converter.

Formats supported by the coaxial input

This point relates to the interface rather than the cable, but it determines the choice. An S/PDIF coaxial connection carries stereo PCM up to 24-bit/192 kHz on most devices, with some limited to 96 kHz. DSD is transmitted via DoP encapsulation, generally up to DSD64. Compressed multichannel streams such as Dolby Digital and DTS also pass through, making connection possible to the coaxial input of a home theater amplifier.

However, high-definition and object-based formats remain beyond the capabilities of this connection: they require HDMI. A CD player, a transport, a network player or a Blu-ray player used as a stereo source remain the natural starting points for this type of cable.

Technical Specifications

Conductors

• 10% high-purity solid silver conductors
  • Solid conductors minimizing electrical and magnetic interactions between strands
  • Increasing layers of silver plating over Long-Grain Copper (LGC) for high-frequency digital signals
  • Superior metal positioned on the outside of the conductor to maximize overall performance
• Optimization dedicated to digital cables leveraging signal surface propagation

Noise Dissipation

• 5-layer Carbon-based Noise-Dissipation System (NDS)
  • Alternating layers of metal and carbon-loaded synthetics
  • Absorption and reflection of noise / RF energy before it reaches the ground-connected layer
  • Shield protection preventing modulation of the reference ground plane
• 100% shielding coverage
• Carbon-based mesh network with directional RF drainage (Coffee Coaxer model)

Insulation and Dielectric

• 72 V Dielectric-Bias System (DBS)
  • Minimization of dielectric noise
  • Linearization of the shunt filter formed by the insulation
  • Improved wide-band dissipation of induced RF noise
• Hard-Cell Foam insulation (HCF)
  • Nitrogen injection creating air pockets
  • No energy absorption or release by nitrogen, reducing distortion
  • Rigidity ensuring stable signal-pair geometry along the entire length
  • Maintenance of stable impedance characteristics
  • Technology related to the foamed PE used on Bridges & Falls cables

Terminations

• Cold-welded
• Silver directly suspended over pure red copper