User Manual

CABLE THEORY

Page 4

is that some of the delicate high frequency information, the upper harmonics, will be smeared. We

hear sound that is dull, short on detail and has a at sound stage. The energy is there, the amplitude

(frequency) response has not been changed, however the information content of the signal has been

changed in a way that makes it sound as though the midrange notes have lost their upper harmonics.

There is a textbook equation which describes the reduction in current and power density at any depth

from the surface of an electrical conductor. For copper the equation is: 6.61 divided by the square root

of the frequency (Hz) equals the depth in mm at which the current density will be 1/e. Since 1/e is 37%,

this equation tells us the depth at which the current density has been reduced by 63%. For 20,000Hz,

current density is only 37% at a depth of 0.0467 mm, which is the center of a 0.934 mm (18 awg)

conductor. Conventional use of the above formula falsely assumes that it is acceptable to have a 63%

reduction in current ow and an 86% reduction in power density at the center of a conductor. However,

this formula does not by itself describe at what depth audible distortion begins. Listening (empirical

evidence) shows that audible distortion begins at somewhat lesser depths.

There is a solution to skin-effect-using a single

strand of metal which is just small enough to push

skin-effect induced audible distortion out of the au-

dio range. Simple evaluation of multiple sizes re-

veals that audible skin-effect induced anomalies

begin with a strand (or conductor) larger than 0.8

mm. A much smaller strand yields no benets but

encourages the problems discussed below.

A common misunderstanding of skin-effect results in the claim that “the bass goes down the fat strands

and the highs go down the little strands.” The surface of a fat strand is just as good a path as the sur-

face of a thin strand, only the fat strands also have a core which conducts differently. In cables with fat

strands which are straight and little strands which take a longer route, the path of least resistance at

higher frequencies is actually the surface of the fat strands. Since the lower frequencies are less sub-

ject to skin effect, they travel everywhere in all the strands.

Misunderstanding Resistance And Other Pitfalls

If a speaker cable used a single 0.8mm strand of copper, it would have too much resistance to do its

job properly. Speaker sensitivity varies, but if the path between the speaker and amplier has too much

resistance, the sound quality will suffer. Such degradation is not actually distortion in the cable, but is

the result of using too small a cable. For this reason, even a short speaker cable should be at least 18

awg (.82 sq. mm) or larger.

Power loss due to resistance is not usually a signicant problem. If a very small cable were to cause

a 10% power loss, the result would be like turning down the volume a fraction of one dB. If a signal

has been robbed of the information that allows you to perceive dynamic contrast, harmonic beauty and

subtlety, we tend to refer to the loss as an “amplitude” loss. However, the signal sounds so dull and life-

less at the far end of a poor cable not because of lost power, but because of added distortion.

Unfortunately, the language of audio very often includes misleading terms. Many types of distortion are

referred to as making the sound “bright” or “dull”, both of which imply a change in amplitude. “Bright” is

often used as a way of saying that harshness in the upper midrange has somewhat the same effect as