How are cables directional?

I’ve read this many times and many cables have directional markings but given that both plugs are identical how is this possible and if so why is it important?

Surely the signal traveling along the cable will be unaffected especially in a cable like Nac A5 which is just copper wire in a single sheath.

Can someone with the proper knowledge please explain.

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This is what atlas cables say;


I am pretty sure the theory is based on the direction that the indivual copper strands are extruded (pulled through an aperture) when made. With one direction being a smoother direction of travel for the signal. How this makes it sound better one way vs the other is beyond me.

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There is also “mechanically directional”

For example, many interconnections have a screen which is earthed (common to ground conductor) at the amp end. Audioquest is a good example of a manufacturer that grounds the screen at one end only.


I would be wary of anyone who claimed to have certain knowledge of how cable directionality influencing sound quality works (or is impossible).

I have never reversed a cable and heard a clearly audible difference in SQ from doing that.

But then I’ve only tried it a few times.

I am open minded about whether cable direction can influence sound quality or not, but it seems likely that it could do in some cases.


That I get but Nac A5?

Didn’t Julian say that they found the directionality came only when the cable sheathing was applied, but they had no idea ‘why’. I think that was reference speaker cable, so either A4 or A5.


Julian posted on this 24 years ago on the old forum. Here’s what he had to say;

"I can’t tell you why cables sound different one way round to the other, but I do
know when the ‘directionality’ happens in manufacture.

It doesn’t seem to matter how the bundle (of copper) is drawn, single direction or mixed direction, but as soon as the insulation is extruded onto the bundle, the directionality is established. This means that one can mark the insulation and it will always be the right way round.

I suspect that the hot plastic insulation anneals the copper in some way, and this affects the crystaline structure.

But all our attempts, over many years, have failed to find any measurement to show the directionality or indeed whether one cable will sound better than another (other than the obvious - resistance, capacitance and inductance)

Maybe someone out there knows?"


With a highly optimised system with which one is very familiar and a familiar piece of music it should be possible to hear a difference when you reverse an interconnect or speaker cables. That difference would be that the previously optimised sound will sound somewhat “off” or somewhat less than it was. You may not immediately think “ah, a cable has been reversed” but it should certainly be one of many possibilities to consider if you had, say, just rebuilt your system and wondered why things weren’t sounding as good as they had done previously.


There is the basis for a Ph D thesis there!


But as the signal is AC, wouldn’t that introduce distortion as either positive or negative flow is inhibited compared to the other? As I understand it there is no direction of travel (not at the physical level anyway)

No because one side is actually hot the other is ground. It’s not + and - .

Can you elaborate how that prevents the issue? Feel free to just provide a link if easier.

For an AC signal the direction of flow through the circuit will alternate. Even if the circuit would somehow only include one of the conductors…

I have absolutely no idea…

I’m not sure I’m good enough to go into that level of detail but I can give you the basics. Both AC and DC transmission consist of a live and a ground, often called the neutral to distinguish it from safety ground in the context of mains, but ultimately they go to the same place.

In AC, the ground (black, negative, return, whatever you want to think of it as) is not carrying signal and this applies for audio too. AC is AC. The current flowing over the return is the inverse applied by the live. For example, early telephone transmission actually use just a single wire. Yes, there was only a single live for the AC audio and nothing else. To make a circuit, the receiving end provided ground as the return. But this proved really noisy so didn’t last long. Still it is good enough for mains AC with TT grounding like in the UK and most of the world in fact. There is only live coming into the house.

Back to line level signals, the poles for phase are still live and ground with live supplying a positive or negative phase and it its reverse current flowing over return.

The only real exception to this is in power amps that use actual push-pull output stages as opposed to the more common live and ground.

So assuming you believe a cable is directional (and in the case of mechanical directionality, they definitely make a difference), that hot and ground are not reversed should matter (speaker cables). However, for non mechanically directional line level cables the all important hot will always be the same pin whichever way round you put it.


Ditto - and whilst I try to retain an open mind I would need to see conclusive results from blind testing to begin to take the idea seriously.

Unlike plain cables connected identically at each end, I can conceive that connecting such a cable, or one with some other non-symetricality along its length such as impedance adjustment componentry at one end of the cable, might have an effect that differs with direction of connection.


Snake oil! To the best of my knowledge, double blind testing has never been conducted to identify cable directionality. Same with “cryogenically-treated” cables. I wonder why???


Then it will probably easier for you, and others, if you continue to take it humorously.


I recall that whenever new reels of cabling would be delivered to Naim, before it was properly released into the factory stores, R&D would cut lengths from various batches and have them made into the appropriate cables - speaker cables, Burndy cables, interconnects, SNAICs etc… Then Roy would listen to them each way around to determine the best sounding direction, and in the case of NACA5, to ensure that the direction marker was correct.

One time there was much consternation because many reels of NACA5 had recently arrived and Roy had listened to some examples and determined that it sounded best the “wrong” way around, i.e. with the direction markers going the opposite way. Much scratching of heads and then corroboration from further listening done by Paul S, Gary etc… So an investigation was made with the cable maker, and, lo and behold, it turned out that a relatively new employee had actually got it slightly wrong and had indeed managed to load the cable the wrong way around for the printing. Roy had, yet again, got it spot on.

Oh, and for anyone concerned about the fate of those many reels of NACA5, they were all scrapped…


I found Julian’s comments quite interesting…

Is it not the case that a relatively new discovery has shown that current does not travel in the wire, but that the electrons actually “ride” just outside of the conductor, at an atomic level?
A further discovery from the so-called “skin effect”…

Could this be what Julian was noticing when discovering that the percieved “difference” happened at the stage of adding the insulation layer?

If the electrons are passing along just outside of the conducter, adding an insulative material directly in their path must surely alter their flow?

If so, could it be possible that the atomic “makeup” of the choice of insulation material could actually be imposing more of a directional effect than the conducter itself?

I am certainly no expert! This is just a theory based upon my reading of such things.
I wonder if we have an atomic scientist lurking hereabouts!?