As ive seen with my own eyes differences in hdmi cables I thought id go hunting for any evidence as to how this could be

Ive since found this

CD TRANSPORT JITTER

The author of the article is a very well respected audiophile and goes to great lengths to find 'why' things work how they do

His test has shown that jitter is influenced by all the following ~

1) the transport's jitter;
2) S/PDIF or AES/EBU interface-induced jitter (the digital interconnect);
3) how well the digital processor's input receiver rejects transport and interface jitter;
4) the input receiver's intrinsic jitter; and
5) how well the clock is recovered and handled inside the digital processor.

"My preconception was that any measurable differences between different coaxial digital interconnects would be marginal at best."

"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."

So to sum up this experiment ~

Cables DO induce jitter 'measureably'

Cables 'can' be directional

Digital cables are NOT the same

Hi All,

Good find Red, goes a long way to describe why we hear differences, although we have known this since our first CD transport ! John you really need to digest the whole article, it covers the RCA cable plug, plus the directional cable conundrum, this study/ claim will need to be substantiated by other professional bodies as this is a first publication of the tests ! look forward to hear more ! ps - so there was something  lacking in the testing of digital signal ?.   ...Carl.

John ~ im in no way even talking to you about this because youll end up getting the thread locked. We ALL know it so dont pretend otherwise

(The link to the ARTICLE is embedded again ~ CLICK IT)

carl kirby wrote (see)

Hi All,

Good find Red, goes a long way to describe why we hear differences, although we have known this since our first CD transport ! John you really need to digest the whole article, it covers the RCA cable plug, plus the directional cable conundrum, this study/ claim will need to be substantiated by other professional bodies as this is a first publication of the tests ! look forward to hear more ! ps - so there was something  lacking in the testing of digital signal ?.   ...Carl.

Don't forget that this article is now 16 years old and even in cheap kit, measured jitter levels have improved by a factor of ten since then (in those days, 44.1kHz sampling was the be-all and end-all. Now, 96kHz and up is commonplace and the higher the sampling rate, the stricter the jitter requirements). Harley's reference source for poor jitter was a Panasonic DAT machine, renowned even in its day for having a very dodgy digital interface.

On page 4 you will see graphs that indicate that the reversal phenomenon is only prevalent when combined with with the poor (Panasonic) interface and Harley concludes (correctly, in my view) that he is seeing evidence of poor cable construction. Later, the article goes on to advocate the use of video techniques and cabling for digital audio - entirely sound advice.

So, the conclusions:

• Digital interfaces need to be designed and built with the same respect that has to be given to a video interface. The industry took a long time to learn that the digital interface is not based on audio techniques, but those derived from the video and RF world.
• A poor interface is exacerbated by poorly manufactured cabling. There is no magic at work here, merely the need for quality components. Video engineers have known this for decades and cabling of a suitable standard is very cheap.
• The industry does learn, albeit slowly. I truly doubt whether this article has much relevance these days except perhaps to the very worst equipment available.

Cheers Pluto,

Did not notice the date ? well i was up early and it was a long read - o well dee dum - !

Cant argue with the date Pluto (I genuinely got mixed up by an article posted from this year on cd jitter on the same site) ~

http://stereophile.com/features/1208jitter/

However ~ we are limited to what we can measure by the equipment available and even if standards have come on a long way (And I sure hope they have), jitter still exists (And possibly always will)

How much difference we as people can see/hear with respect to jitter is another question entirely (And of course person dependent)

When you say 'suitable standard' you mean that cables do make a difference ABOVE the 'suitable standard' you speak of?

Red Dwarf wrote (see)

However ~ we are limited to what we can measure by the equipment available and even if standards have come on a long way (And I sure hope they have), jitter still exists (And possibly always will)

How much difference we as people can see/hear with respect to jitter is another question entirely (And of course person dependent)

The answer to that is open - the article's conclusion states

"There is no consensus about what levels of jitter in a digital product's output are acceptable—the audibility will depend on both level and spectrum". I might add that it also depends, greatly, on sampling rate. The requirements for 192kHz sampling are vastly more stingent than for 44.1kHz Red Book.

Red Dwarf wrote (see)

When you say 'suitable standard' you mean that cables do make a difference ABOVE the 'suitable standard' you speak of?

No, a well engineered cable (or anything for that matter) is suitable for the job in hand and it's pointless going any further. I don't know just how good the cables are that you buy. What I do know is that the quality of a cable is not related to its retail price. For digital use I favour cables that are specified for video, typically terminated with BNC plugs. If you are paranoid, for a few quid more you can have cables specified for SDI video; they are good to the GHz region. If you need phono terminations (and that's where the problem often exists) the best way is to get BNC to phono adaptors which are absolutely co-axial in construction, unlike any native phono plug that I know of.

So for the very best SPDIF lead that money can buy get these and put a couple of these on the ends.

Pluto ~ thank you for your input

Id have said so earlier but when I first looked your reply was 'h h h' for some reason 

John Fisher wrote (see)

Please please again can anyone explain HOW a cable can introduce jitter. 

I suspect it can only happen with the combination of a very poor interface (like the Panasonic DAT machine cited earlier) and poorly constructed cable. Unless the graphs given in the 1993 article are fabricated, they ought to be taken at face value and ONLY poor construction could explain those anomalies.

Jitter is most certainly a function of cable length; I've measured the effect myself. A 30m AES cable appeared to add about 20pS of jitter. Measurable but insignificant.

Another point that needs to be said is compared to 1993, modern digital receivers are FAR less prone to jitter-induced problems than they were then. I've been to a demonstration where unfeasibly large amounts of jitter were artificially added to no audible effect. In fact, the arrival of audible artifacts and the incidence of data corruption were remarkably close. How odd!

John Fisher wrote (see)

I still do wonder how a cable can ADD jitter

I suspect its related to the fact that the 'squareness' of the transitions reduces with increasing signal degradation i.e. the distinction between the two signal states becomes less precise. The consequence is that it becomes increasingly difficult to determine the precise point of transition and this uncertainty manifests itself as noise; jitter.

However, I must emphasise that this is academic as any decent digital interface should be largely immune to to the few pS of jitter that could be added by an interconnect, and then only a rather long one.

John Fisher wrote (see)

Sounds like a plausible reason, but like you say is rather academic as the data rate from a CD is pretty slow compared to say a CAT5 computer link. And that is slow compared to an HDMI link and neither suffer the jitters...

ahh ~ as PLUTO says

I see