I need help on directionality of speaker cables

"In the transmission of the signal in digital cables, electron travels down the cable at the frequencies used by audio/video signals. The higher the frequency of the signal, the more this signal is pushed to the surface of the cable, and the skin of the conductor itself carries a considerable portion of the signal."

Ryder, where is this info from? The reason I ask is that a digital signal, by it's very nature, doesn't have frequency in the way analog signals do. As I've quoted above from a reputable book on electronics, a digital waveform is a DC signal that varies between zero volts and a max volts, with no in-between.
Skin effect, whilst it exists in analog transmission (especially video), is not relevant in digital data. That's why HDMI and digital RCA cables don't need to be silver-plated copper. The bitstream of digital data is either 0's (zero volts DC) or 1's (eg. +5 volts DC). The quality of the cable will impact on how much data loss or errors occur, and can cause timing errors, but it isn't carrying any frequencies as such in terms of audio or video frequency.

The only time you really need to consider the 'skin' effect is when using analog video, such as S-video, component etc.

My last word on this subject, which might cause more discussion!!
Electrons don't travel down cables like water through a pipe. They are transferred from one atom in the conductor to another, somewhat like pressure in a hydraulic line is transferred. If one injects 10 electrons (applies a voltage at one end of a circuit) then the 10 electrons displace 10 electrons in the first conductor atoms and those electrons displace 10 electrons in the next atoms etc. The original 10 electrons don't appear at the end of the circuit as some would believe. Depending on how the electron transfer is 'impeded', a different quantity of electrons is transfered to the final element for the same voltage. Thus if the final element and conductor offer a high impedence the current can indeed be very small, but the voltage at the final element still be sufficient for that element to get the 'message' (signal) and do its thing, amplify for example.

Salut, Bob P.

Carl109,

If you would do a search there are abundance of details of skin effect that do occur in digital interconnects, be it SP/DIF or AES/EBU. This is just one out of the many references that describes this.

http://www.psaudio.com/products/xstream_digital_moreinfo.asp

You have to scroll down abit though. I didn't provide any links earlier as I thought nobody would be interested to have a look (since Bob didn't read the earlier link by Stereophile). And just if anyone wants to know more about skin effect, here is the description in Wikipedia.

http://en.wikipedia.org/wiki/Skin_effect

Probably your reference book doesn't mention anything on skin effect in digital cables? Anyways, the main question that remains is whether there is any direct correlation between AC(non-directional) and directionality in cables. There is no definite answer to that I would really like to know as well.

Ah yes Ryder, but from the Wikipedia link you posted: "The skin effect is the tendency of an alternating electric current (AC) to distribute itself within a conductor so that the current density near the surface of the conductor is greater than that at its core."

Even this notes that the skin effect is specific to AC current.

Transmission of digital data, as I quoted from the electronics text, is DC.

Put these two facts together and "skin effect" is not relevant to digital data transmission, and so cables for such DC digital data do not need to take it into account.

QED.

Wow, this thread got carried away down the wrong road.

As an EE, the way I see it is that cables with direction arrows on them are solely to get the shield grounded properly. End of story. If they have no shield, there is no good reason for the arrows that I can see.

Skin effect is a function of frequency so DC signals never see it.

Arthur