Directional wires/cables

Wow, all this technobabble is giving me a splitting headache.  I received my EE in 1976.

@stereo5 

Were you taught the signal travels in the wire or travels in the spaces between the wires?

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I first learned how electricity works here on Agon in 2010. Oddly the thread was titled "directional cables?".

The only bit of cable directionality I believe in is the shielding.

Shields should be connected to ground at the active end, which is the source. Hence shielded IC’s should have an arrow pointing from the source to the destination.

If you are using a shielded cable, then noise performance will be better when this is adhered to. Otherwise, no. Makes no difference at all.

Most homes aren’t near enough sources of noise for this to matter either way, but if you are, then pay attention to the direction.

Of course, this applies only to 2 conductor + shield wires.  If your shield is the ground, then its' the same either way.

I’ve referenced this I don’t know many times over the years. The article is from 1993. Old yes. Wires have been around a lot longer than that.

Actual measurements for those that say, "If it can’t be measured then it can’t be true."

After measuring the first two products (the PS Lambda and the Panasonic SV-3700), I went back and repeated my measurements to make sure the analyzer was giving consistent results, and that my test setup was correct. When I remeasured the SV-3700, I got about half the jitter than when I first measured it!

What caused this reduction in measured jitter?

Changing the direction of the digital interconnect between the transport and the jitter analyzer.

This phenomenon was easily repeatable: put the cable in one direction and read the RMS jitter voltage, then reverse the cable direction and watch the RMS jitter voltage drop. Although I’d heard differences in digital-cable directionality, I was surprised the difference in jitter was so easily measurable—and that the jitter difference was nearly double.

To confirm this phenomenon, I repeated the test five times each on three different digital interconnects. One was a generic audio cable, the other two were Mod Squad Wonder Link and Aural Symphonics Digital Standard, both highly regarded cables specifically designed for digital transmission. The generic cable wasn’t directional: it produced the same high jitter in either direction. But both the Wonder Link and the Aural Symphonics had lower jitter levels overall, but different jitter levels depending on their direction. Moreover, the generic cable had higher jitter than either of the two premium cables—even in the latters’ "high-jitter" direction.

Fig.8 shows the jitter difference between cable direction in Wonder Link using the Panasonic ’3700 as the source (the difference was about the same in the Aural Symphonics). Note that, at these high levels, small differences in the trace are significant. Between "10m" and "0.1" on the vertical scale, each horizontal division is 100ps. The overall RMS jitter was 4050ps with the Wonder Link connected in one direction, and 2700ps with the cable reversed.

https://www.stereophile.com/features/368/index.html

JMHO, there can’t be an honest discussion of cable directionality if one believes the signal travels back and forth from the source to the load. Especially at near the speed of light in a vacuum.

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@jea48  Thanks a lot for posting the results from that article.  As per my previous post I inadvertently installed my digital cable backwards once and my system literally sounded broken until I figured it out and installed it correctly.  It was not subtle at all, but until now I hadn’t seen anything that explained technically why I clearly heard what I did.  Those who poo poo the directionality of cables can go pound sand.  It’s a real thing.