Directional cable - AVS Forum
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post #1 of 9 Old 01-05-2007, 09:17 AM - Thread Starter
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I read something odd yesterday. Over 10 years ago, Stereophile used a jitter analyzer to analyze the jitter output from various devices. As I interprted the article, they wanted to see if what they heard could be correlated to jitter.

I am not sure they proved that after reading the article.

What did intrigue me was reducing the jitter caused by one cable by reversing it! This is hard to believe. They claimed that hooking it up in one direction DOUBLED the jitter.

I had heard the theory before that cable could cause jitter (due to impedence mismatches etc.) But reversing the cable?? Could it be an issue of poorly made connectors? That someone reversing the cable improved the impedence matching? I really have no clue.

Thoughts?

Link:

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

"But this one goes up to 11"
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post #2 of 9 Old 01-05-2007, 10:07 AM
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Looking through the article I didnt see the cable swap thing. What page is it on?
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post #3 of 9 Old 01-05-2007, 11:12 AM - Thread Starter
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I posted the wrong link! Many apologies. The new link should be correct. Read page 3 for the specifics on cable directionality. Reading it again, he also suggests the connectors as a source of jitter.

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post #4 of 9 Old 01-05-2007, 11:43 AM
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The important part Quote" I performed the same tests using the low-jitter PS Audio Lambda transport as source. The results were very different. With a good source, cable direction didn't make a difference in the measurable jitter (fig.10). This suggests that the SV-3700or any poor-quality transmitterreacts with the cable's impedance to create jitter-inducing reflections in the interface. The directionality was probably caused by differences in the way the two RCA plugs were soldered to the cable; any bumps or discontinuities in the solder or RCA plug will cause a change in the characteristic impedance, which will cause higher-amplitude reflections in one direction than in the other. These reflections set up dynamically changing standing waves in the interface, introducing jitter in the embedded clock. These problems were reduced by the Lambda's higher-quality output circuit. "

It seems the connection had something to do with it.
Important to point out though that the GENERIC CABLE was NOT directional, but did have more jitter over all.

Now did the cables they measure that were directional have arrows on them?I suspect not as he didnt point that out. If not then its just a fluke of the cable like he said.
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post #5 of 9 Old 01-05-2007, 11:57 AM
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Let's see if I get this.

The fellow measures something.
He flips the cable.
The measurements change.
He calls it significant.
He guesses that it is a difference in attachment quality between the two end connectors.
He imagines that the difference is a change in impedance. AND
That difference causes a change in the magnitude of reflection. AND
Dynamically changing standing waves are induced.

He does not measure the cables.

He does not consider the possibility that unplugging and reconnecting the cables is itself a factor

But he does note that the difference is also a function of the device being measured. The greater the device error, the greater the impact of the cable direction.

Oh, and it is also a function of cable cost.

This is an example of why I no longer am a subscriber to Stereophile. It looks like science, but it wanders into wine tasting. Kal Robinson and some few others excepted.

The fact that an opinion has been widely held is no evidence whatever that it is not utterly absurd.
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post #6 of 9 Old 01-05-2007, 01:26 PM
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Trek good points i was really giving him alot of rope.
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post #7 of 9 Old 01-05-2007, 03:20 PM
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As I understand it, shields are typically grounded at one point only, i.e. at one connector. That might make a difference in impedance.

Otoh, does it matter? Were even the golden ears able to identify a high-jitter circuit?

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post #8 of 9 Old 01-05-2007, 04:18 PM
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Quote:
Originally Posted by DMF View Post

As I understand it, shields are typically grounded at one point only, i.e. at one connector.


There are many different opinions on this. Some say to lift the shield on one end andothers say not too. There are even differing opinions on which end to lift the shield. I never do this and have never ran into a problem.

Matt D. Sherer CET, CTS-I,ISF-C
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post #9 of 9 Old 01-08-2007, 03:41 AM
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Well, it's an old article and they didn't do a lot of replications did they?

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