Dielectric Absorption in Cables Debunked - Measurements

If we examine an allegedly horrible cable regarded by many so called audiophiles (12AWG Zip Cord), we can see the effect of Skin effect (increased AC resistance, decreased internal inductance).

We learned how to calculate inductance of speaker cables in Calculating inductance of twin feeder (Zip Cord) . This concept can be used for all cable geometries, but the math becomes somewhat more complex using superposition for multi conductor insulated Litz style construction. However, this goes beyond the scope of this article and the point here is to show that at audio frequencies the inductance remains extremely uniform, thus the increase in skin resistance is NOT significant enough to minimize internal inductance.

Here we see a slight elevation of AC resistance due to skin effect at 20khz. But when we look closer we see note the DC resistance of the cable is 3.27 mohms/ft and the Rac at 20kHz = 3.31 mohms/ft which represents a meager 1.2% increase in resistance due to skin effect. To put this in terms of signal power loss would be: 20*log (3.27/3.31) = .051dB! Studies in acoustics have proven the human ear is not capable of discerning level differences of less than about 0.5dB which is 10 times greater than the loss we see from Skin Effect! In addition, the human ear is extremely insensitive to amplitude changes at very low and high frequencies based on the Fletcher and Munson Curves . Check out our article for an in-depth look at Skin Effect and how the human ear works, check out our Physics tutorial .

Here we do see the capacitance decreasing with frequency but not because of Dielectric absorption. What we are seeing here is a combination of slightly decreasing dielectric constant with frequency and slight fluctuation in measurement due to instrumentation error of cable inductance isolating the very small value of capacitance as frequency increases. The most accurate measurement of capacitance in this case is from about 1kHz to 10kHz. If we take an average value, then 14pF/ft seems reasonably accurate.