high end audio

The Challenge Of Interconnect (Low-Current) Cable Design
If you haven’t read the previous discussion of problems in speaker
cables, then please read that first. The following is meant to build
on that foundation. The same problems exist in both high-current
(speaker) and low-current (interconnect) applications. However, the
hierarchy among these problems differs.
In low-current cables; skin-effect, electrical interaction, magnetic interaction
and conductor quality are still primary problems. The negative
sonic effect of internal mechanical modulation due to magnetic
fields is greatly reduced.
The electrical behavior of the dielectric (insulating material) is much
more important in low level cables. Dielectric involvement (the way
in which a particular material absorbs and releases energy), has a
profound effect on an audio or video signal. Dielectric constant, the most often quoted specification for
insulating material, is actually not very helpful in understanding the audible attributes of different materials.
The coefficient of absorption value is more relevant, and the dissipation factor and the velocity of
propagation are even more useful.
The problem is that any insulating material next to a conductor acts like a capacitor which stores and
later releases energy. This is true of circuit board materials, cables, resistors and of course capacitors.
The ideal wire is one with no insulation except for air. When a solid material must be applied, it should
be electrically invisible, meaning that the less energy it absorbs, the better. The energy which is absorbed
should stay absorbed (turned into heat, a high dissipation factor), and the energy which does
come back into the metal conductor should have minimal phase shift and not be frequency selective
(a high velocity of propagation, independent of frequency). All dielectrics absorb more energy at higher
frequencies, but some are more linear in their overall behavior relative to frequency.
The most commonly used insulations are PVC, polyethylene, polypropylene and Teflon. These can be
mixed with air (foamed) or applied in ways which maximize the amount of air around the metal strands.
Which material is used and how it is applied will dramatically affect the performance of a low-level cable.
Capacitance is more important in low-level than high-level cables for two reasons. If a long, "over the
cliff" high capacitance cable is used, many preamplifiers, CD players, tuners, surround processors, etc.,
will not be able to "drive" the cable. The resulting distortion does not happen within the cable, but is
caused by using the cable. There is never a disadvantage to using low capacitance low-level cables.
The other important reason for low capacitance is that high capacitance causes greater field strength
between the positive and negative conductors (and the shield). This means more energy is put into the
dielectric material. There
is always a priority to minimize dielectric involvement, through proper selection
of materials and low capacitance design.