Directional Audio Cables - myth or reality?

 

Digital is a whole different ball-game and you are moving from Audio into RF (which is why your digital cable is a co-ax cable like your TV) - in these cases optical is better.

I have sent an email to Kimber Kables, (surely that should be Cimber Cables - swaping K's for C's is all a bit too much Kamelot and Konkhra for me), asking if they could furnish me with more details on this quantifable test method. I await their reply.

 

Mike is correct on all counts - if the cable were electrically directional then the symmetry of the signal would be affected - ie distorted on one half of the signal - swapping the cable would only swap the distortion to the other half but the net result would be the same... distortion.

 

::thinking out loud::

 

Because this distortion would be asymmetrical it would consist of predominately even harmonics - the same kind of harmonic distortion you get from the output transformer in a valve (tube) amplifier. Valve amps are generally regarded as "warmer" than their solid-state counterparts for this reason. However since this asymmetric distortion is the same in both directions it does not explain subjective directionality.

 

In all of the (web)published info on this subject many listeners say that the signal sounds warmer when the cables are swapped while the others say it is brighter (i.e. the opposite). Aside from sugesting that the actual direction of these "directional" cables is purely a matter of personal taste, it tends to imply that there is even harmonic distortion in one direction (warmer) and odd harmonic distortion in the other (brighter). Odd harmonic distortion occurs when the music signal is distorted equally on both the positive and negative cycles (ie symmetricaly).

 

This leads to another possible explanation in that in one direction there is odd harmonic distortion and in the other there is none. What people are perceiving as a warmer sound is actually the true sound that the record producer created and the brighter sound is the cable distorting the signal symmetrically. This still does not explain the mechanics of subjective directionality.

 

A cable is a passive network, electrically it is described by transmission-line theory, which describes the two wires (signal & return - not left & right) as a ladder of series inductors (L) and parallel capacitors (C), this is symmetrical and (being passive) works in either direction. The inductors are the wire itself while the capacitors are the plastic insulation that seperates the two wires (often called the dielectric... and there is a whole mess of audiophile psuedo-science regarding dielectrics - including one idea that the dye in the insulator can leach into the wire). This L-C effective-circuit is a low-pass filter, with a roll-over frequency in excess of 100KHz (depending upon cable length), which is why you cannot send video signals down an audio cable. Because audio cables are designed to have a flat frequency response across the entire audio spectrum the electrical characteristics of the cable cannot be affecting the colour of the sound like the tone-controls on an amplifer would.

 

For there to be directionality in this L-C ladder then either there is either directionality in the L or in the C element of the cable. All internet discussion on this subject centres around the wire itself, which suggests that the directionality is in the wire. However, since the conductors are multi-strand then this directionality would have to exist in all the individual strands and that they are all aligned in the same direction.

 

Because multistrand cables are spun together from multiple reels of single strand wire this would mean that the spools of wire are all of identical directionality. As strange as it may seem - this is feasible since the wire is made by drawing a ingot of copper through increasingly smaller dies, then spooling it onto a huge drum and then re-reeling it onto smaller spools for sale to audio-cable manufacturers - so the direction of manufacture will be constant for all spools. If it is the drawing process that imparts the directionality into the inductance of the wire then it will be electrically measureable. And since both wire and the ability to measure inductance have been around for a few hundred years, someone would have spotted this by now. Even cable manufacturers who sell directional cable only quote one value for the inductance of their cable (and one value for the capacitance).

 

On curious comment I read on this subject is that the directional effect is less noticable after 20 minutes or so.

 

This process is refered to a lot and is called burn-in, impling that there is an annealing effect going on, which, by inference, means that heat is involved in re-arranging the structure of the copper. Heat requires power. The power in an interconnect is smaller than miniscule - the resistance of the cable is typically 65miliohms and it is terminated in 47Kohms. This means that for a 1 volts rms music signal 1.46uV is lost in the cable, which equates to 40attoW of power (40E-18W), which is best refered to as four-fifths of nothing divided by infinity. One fanciful explanation I have read for this is that the electrons flowing through the wire are rearranging the copper crystals to find the path of least resistance, which is wrong on so many levels I'll not even bother to comment.

 

Another cable-direction issue that is costing Audiofiles a whole heap of readily disposible cash is in the power cable that connects the hi-fi to the national grid. But that's another story.

 

 

 

i too would be interested to know what  "new and very expensive test equipment" they use to test directionality, might write to them myself and ask for a report!

 

 

 

I've got the feedback from Mr Diamond of Kimber Kable. The copper wires they use are basically amorphous in structure, and hence not directional. He says that directionality occurs after a burn-in period. He also states that they have some expensive test equipment and can perform some special tests at special frequencies that reveals observable changes that standard audio-band tests would not show.

 

 

 

 

 

So the real irony is not that Audiophile believers are wasting their money buying unnecessary directional cable, but that we sceptics and non-believers could be using "directional" cable anyway.