1. Low Capacitance
This is possibly the most important audible aspect, Interconnects transfer analog voltage signals between components. The voltages involved range from < microvolt to over +1 Volts, but the currents involved are always extremely small. The currents are small because the load that the interconnect drives is generally between 10-100K ohms. This is the input impedance of the component being driven. There is virtually zero power transfer with interconnects.
Because there is basically zero power transfer, it is not necessary for the driving component to be capable of driving much power. As a result, most components are designed with an output impedance of between 7 and 200 ohms. Lower is better because the driver is less "sensitive" to the load. However, the load is actually comprised of a resistive part and a capacitive part.
This capacitance is caused by the integrated circuit or transistor packaging, the printed circuit board traces and the silicon itself. This capacitance presents a load to the driving component. If the capacitance is too large, the high-frequencies will begin to attenuate or decrease due to the loading on the driver. The input capacitance of a component is generally never characterized (not in the specs), but this is actually as important as the resistance. The interconnect also adds to this capacitance and can actually contribute more to the total capacitance than the receiving component. It is therefore an object to minimize the capacitance in an excellent interconnect.
The capacitance of in interconnect is a function of its length. The longer it is, the higher the capacitance. This is why interconnect length should generally be minimized. Interconnect capacitance is also function of geometry and dielectric material. Capacitance is minimized by spacing the two conductors apart as much as possible and by avoiding parallelism. It is also minimized by using low dielectric-constant materials between the two conductors.
(In AC power cables high capacitance will also affect stereo imaging, and many other aspects that will be discussed in another post)
How do we minimise capacitance in A.L.A. cables?
- Air dielectric is used between the two conductors where possible, a good example is our Zircon range.
- Where air is not possible, Teflon or other low-dielectric constant materials are used
- Conductor parallelism is avoided by geometry
- Conductors are spaced apart, Once again our Zircon range is a perfect visual example of this design principal
2. Minimize skin-effect
Skin-effect occurs when the high-frequency currents flow on the outer "skin" of the conductors whereas lower frequencies have more uniform current distribution across the conductor cross-section. This happens when too large a gauge is chosen for the conductors. The effect is that the impedance (primarily inductance and capacitance) is different for low frequencies than high frequencies. This difference in impedance can cause attenuation and phase shifts in high-frequency passages relative to low-frequency passages, causing a smearing effect to the music. If a sufficiently small gauge is chosen for the conductors, all frequencies are "forced" to flow more uniformly in the conductors, effective eliminating skin-effect. Skin-effect is also a function of conductor material.
How does we minimize skin-effect in A.L.A cables ?
- Careful selection of conductor gauge and stranding to insure optimum low and high-frequency response.
- 99.99% Pure Silver conductors ideally, or high purity coppers
3. Minimal use of conformal coatings
Conformal coatings (insulation) on conductors create a non-uniform dielectric medium around the conductors. This dielectric material stores energy from the conductors in the form of charge. Similar to a battery, the dielectric material prevents the conductors from discharging immediately and completely when the music waveform demands this. The result is that latent charge is still present in the dielectric material to be released when it is not desired. The technical term for this effect is Dielectric Absorption. This effect is more pronounced in less expensive cables that use PVC for insulation rather than Teflon or other low dielectric-constant materials. This has two detrimental effects:
Latent charge can change the amount of energy required to charge the dielectric, drawing less current with some passages than others from the driver. Latent charge can appear on the conductors when it should not be there. Either of these effects can conceivably cause "smearing" or dispersion of the audio signal, particularly between left and right channels, where this can become audible to humans.