Elfasto,
Do you have any opinions on "dielectric absorption" effect on the sound we hear? Thicker cables usually have thicker insulation, ergo...
I have my findings, just curious about yours.
Again, this is just my 2¢ and based on mathematics, measurement, and observation with my system.
Most cables do have capacitance, which is natural because we have 2 conductors separated by a insulating material. When I measured my cables I did have a great variance in each cables capacitance.
So, I tried a variety of cables I had at hand (80% were premade 6 foot, and a couple of premade 3 foot cables), ranging from the thin el-cheapo ones that came with the stereo components, Monster Cable Video grade, RCA video grade, Acoustic Research Video grade, and a Acoustic Research Subwoofer Coax cable (aka really frickin thick cable).
Now, in all the 6 foot cables I tested, the one with the lowest capacitance was the 6 foot Acoustic Research Subwoofer cable (105 pF).
All the rest of the 6 foot video grade cables (Monster, RCA, Acoustic Research) were with a range of 128 pF (RCA) to 280pF (Acoustic Research, Monster).
The 3 foot cables were fairly low, and the majority of the "better" 3 foot cables were around the 50pF, and the el-cheapo ones were around 70pF.
So, the variance in cable capacitance is HUGE. Length does play a role in the capacitance, but the material also does as well.
Now, For audio, I DID NOT find a appreciable difference between the cables, save for noise due to one's cable having better shielding than the other, and that was readily noticeable between the el-cheapo cables and the video grade cables. All the video grade cables had better shielding and lower noise. The sound quality with various cables was almost the same across the board with every cable, doing A-B testing, Left and right channel cable differences with a mono source, and long term listening.
So, IMHO, capacitance in a cable will not play a serious role or any role in a audio system as long as the lengths are short (6 feet and under) and purposely routed away from any high tension lines (i.e. 120V, 220V, 240V power supply cords) that usually have absolutely no shielding on them whatsoever. The capacitance is just too small and the frequencies that the cable's capacitance would affect is just too high and beyond the audible frequencies. If a cable gets exceedingly long, cable capacitance may come to play, but there are other losses in a very long cable that will come to influence the sound and signal propagation far sooner than cable capacitance in Audio frequencies.
For analog video, cable capacitance plays a larger role. Because the bandwidths of video being so wide and the frequency range going up into the MHz, a cable's capacitance can be seen readily as a poorer or better picture. For my setup, the Acoustic Research Subwoofer Cable won out because:
1) I needed a 6 foot cable to go between the Laserdisc player and my Vizio 47" LCD TV.
2) It had the lowest capacitance of all the 6 foot cables, and the TV picture was the best with this cable. Colours were sharpest and picture was generally better due to less video noise.
So for high to very high frequencies, a cable's capacitance will be an issue because the frequencies needed for analog video extend high enough that the cable will act like a filter, a attenuator, and drop your signal strength or portions of your video signal.