Quality of digital cable from from source to DAC?

Todd.  Let me try to explain jitter.  Imagine you play 1kHz sinewave recorded on your CD.  Digital words of changing amplitude, representing sinewave, are converted in even intervals into analog values by D/A converter.  You get analog 1kHz sinewave.
Now imagine that these time intervals are not exactly even, but are getting shorter and longer 50 times a second.  Now you won't get only 1kHz sinewave but also other frequencies, mainly 950Hz and 1050Hz called "sidebands".  Distance from the main (root) frequency depends on the frequency of the interval change (jitter), while their amplitude is proportional to amount of interval change.  These new sidebands have very small amplitude, but are not harmonically related to root frequency (1kHz) and that makes them still audible.
With many frequencies (music) there will be many sidebands - practically a noise added to music.  Sidebands have small amplitude that is proportional to amplitude of the signal.  This noise stops (is not detectable) when music stops playing.  You can only hear it as lack of clarity in the music (since something was added).  

Many factors can produce D/A conversion clock jitter.  Cable can be one of them, while injected electrical noise can be another.  In case of Ethernet or USB cable cannot affect timing directly, since samples are placed in the buffer ahead of time, but cable can still inject electrical noise into the DAC. 

Jitter can be induced by one noise frequency (correlated jitter), like 50Hz in our example, or by multi-frequency electrical noise (uncorrelated jitter).  Effect of jitter is less audible when frequency of the jitter is low, because sidebands will be closer to root frequency, hiding better (less audibly visible) . Also random jitter (uncorrelated) should be less audible, being sort of averaged.

(As for 90% speed of light it is more like 60-70% dependent on the dielectric.  I assume about 5ns/m)

Thanks again to everyone's input.

kijanki, your's is one of most thorough explanations I've encountered. Thanks for that effort. Occasionally do some sea kayaking. There are seemingly always some occasions where, due to any number of factors (i.e. changing wind speed, water depth, shore reflections, etc.) that what are typically dependable and predictable wave movements become what are referred to as 'confused waves'. Guessing on a micro-scale, much the same applies with electrons in a sea of copper wire. Sorry, I live by association. Don't know that it's an accurate correlation, but seems like maybe it ought to be?
andy2, please note this is in NO way a challenge to what you say, but simply for me to express my lack of understanding. '2. It's electrical signals' I totally get. What I question (because I have NO idea) is that are they two different 'ways' (for lack of better word) that the electrical signals are transferring information?

My perception (and this is what I'm SO hoping to clean up) is that the source (server/cd/whatever) transferring the data of a 'digital' file by emitting electrical signals in simple (relative to analog), concise, rigidly defined, regulated pulses (the ones and zeros) are painting a complex (understatement) 'coded' picture (maybe movie's the better term, as it's constantly changing?) that the DAC must decode and translate into an analog electrical signal.

The electronic 'digital' signal carrying this coded information deviates little to none (I would think?) in amplitude or frequency. The electronic signal (pulse) is either go, or no go, yes or no, (1 or 0), and sequenced to relay a defined coded message that the DAC can interpolate. Given the velocity of an electrical wave through a copper (or silver)  wire is deemed to be roughly 90% the speed of light, essentially instantaneous relative to the lengths of cables in our systems, seems that 1. deviations in the devices 'clocking' mechanism or 2. potential electromagnetic interference from surrounding electronic wave movement could really be the only sources to alter the passage of this data transfer through a wire.    

Electronic signals transferring analog information (I would think) are another animal altogether, deviating in both frequency and amplitude, and in turn being more more complex signal transfer that would be susceptible to alteration (error) in part due to its complexity. 

With this point of view (wrong as it likely is), seems that other than obtaining the best possible shielding there would be little to gain relative to different cables in transferring digital (coded) information, where as with the complexity of an analog electronic signal would actually benefit from a transducer that imposed as few impediments as possible to the electrons path.    

Well aware this is absurdly simplistic in (my) thought and supremely complex in reality. And I reiterate for any one reading what I've written, this in all likelihood IS NOT how things really work, again, it's only my perception. Not all that bright here, but smart enough to know it's likely way off in reality...
Came across an 'jitter' article that seems both broad and approachable (for us not so technically aware), in case anyone's interested:
http://www.enjoythemusic.com/magazine/manufacture/0509/
Not asking that anyone write a dissertation to cleanse my ignorance to the matter, but if anyone can at least guide me towards some reading that might enlighten me in my quest to (at least sort'a) know how it really works, will be much appreciated.
Todd 

 

 

 

 

@ecolnago
All digital cables affect sound of the DAC differently.  In order to make sure DAC receives just right amount of data it has to synchronize internal D/A conversion rate with incoming data (S/Pidif) or receives data at different rate, but signals back to increase or reduce amount of incoming data (async USB, Ethernet).  In case of async USB or Ethernet D/A conversion clock is independent of incoming data timing, but it might be affected indirectly by noise injected by the cable into DAC. S/Pdif delivers data in real time and the average rate of this data adjusts rate of D/A conversion. S/Pdif cable can affect this rate two ways. Coax S/Pdif cable transitions are fast, hence susceptible to electrical reflections in the cable, that add to and modify shape of transitions affecting timing. DAC corrects most of it by adjusting to average of the frequency, but it is not perfect. In addition cable injects picked up electrical noise. Optical cable is different. It doesn't inject electrical noise and doesn't create ground loops (like coax cable can), but transitions are very slow. Slow transitions in presence of electrical noise can affect exact moment in time of level recognition (crossing threshold). It all comes to making clock of internal D/A conversion stable in time. Jittery conversion clock produces noise added to music.

In case of Ethernet or USB I would pay attention only to quality of shielding and run cable away from other cables. Same goes for coax S/Pdif, but matching characteristic impedance of the cable (to avoid reflections) is also very important. It is also desired to keep cable very short - less than foot (to avoid reflections) or longer than 1.5m (to avoid first reflection).  With optical cable, quality of the cable (clarity, etc) plays role, but the most important is to keep system electrical noise low, by using power conditioners for the source of the signal and the DAC.

These kinds of discussion will get nowhere. Anyway here are facts:
1. It’s not zero’s and one’s.
2. It’s electrical signals.
3. Once you connect A to B, A will affect B electrically regardless.

mike_in_nc
>>But my desire to have understanding of most things is strong, particularly when they effect both my happiness and my wallet. <<

Such understanding is where you will find the most divergence of opinions about cables. Manufacturers -- and their customers -- have many hypotheses about what makes certain cables special. (I use "hypothesis" in the scientific sense, to mean an unproven yet plausible idea -- what non-scientists often call a "theory." A theory in science is something supported by overwhelming evidence.) Most hypotheses about cables are not supported by unbiased science. Given that, it becomes a matter of what sounds better to each individual. For various reasons, it’s easy to lose the distinction between slight differences and clear improvements.

>>>>I actually don’t agree with the major points of your paragraph. It all depends on who you talk to what theory is involved, what is fact, what is evidence and what breaks some sacred Law of Science. And to a large extent on whose ox is being gored. Yes, I know what you’re thinking - well, somebody must know. 🤗

>> But my desire to have understanding of most things is strong, particularly when they effect both my happiness and my wallet. <<

Such understanding is where you will find the most divergence of opinions about cables. Manufacturers -- and their customers -- have many hypotheses about what makes certain cables special. (I use "hypothesis" in the scientific sense, to mean an unproven yet plausible idea -- what non-scientists often call a "theory." A theory in science is something supported by overwhelming evidence.) Most hypotheses about cables are not supported by unbiased science. Given that, it becomes a matter of what sounds better to each individual. For various reasons, it's easy to lose the distinction between slight differences and clear improvements.

There are strong incentives for manufacturers and dealers to steadily increase the prices of their products, as well as to offer numerous products at various price levels. Whether they do so in good faith is not for me to say.

Like I said before, show me in operation some optical glass fiber RCA interconnects, and we can start to conflate the discussion of analog and digital transmission.

ecolnago
Have had opportunity to acquire several credit hours of physics, thermodynamics, etc. in my earlier years. While I can’t necessarily hold an in-depth conversation on ALL the various aspects involved as electricity passes thru metal, I do have at least a little understanding of that physical process and many of the factors/elements that might affect it.

>>>>Don’t be shy. Please share. I’ve been trying to get just that, an answer to the dodgy question, “what is the audio signal,” for some time.

Thanks everyone for your time and effort given.

Twoleftears, waded thru some of the silver/copper discussion and remain perplexed (as I believe was your intent to display I am certainly not alone) that little mention was made to the differences (if any do exist?) in the movement of digital signals vs. analog signals.   
Wow Mitch, thanks for your input and effort with all the relative links. No doubt to be intriguing reads.

I will be letting my ears and wallet that will determine MY take on this. Am comfortable knowing that some things in life (for which this may be another instance) simply defy explanation. But my desire to have understanding of most things is strong, particularly when they effect both my happiness and my wallet. Wish it were easier to do some blind-tested cable swapping myself, but for numerous reasons this is not likely to ever happen. Too many hobbies and desires. So just trying/hoping to make the best out of learning thru others reported efforts and experiences.  

Have had opportunity to acquire several credit hours of physics, thermodynamics, etc. in my earlier years. While I can't necessarily hold an in-depth conversation on ALL the various aspects involved as electricity passes thru metal, I do have at least a little understanding of that physical process and many of the factors/elements that might affect it.

Hoping some of the links offered might delve into the differences (if they exist?) between the movement of digital data vs. analog data thru metal cable runs. This I have little to no understanding of.   

Lots of opinions on this subject but, as with any other cable debate, the only conclusion that matters is yours, based on what you hear in your own system. Even more than with other analog cables, opinions regarding the relative quality of different RJ-45 cables seems to be a crapshoot.

The range covers those who believe there is absolutely no difference in digital cables (i.e., the zeros and ones crowd), those who hear differences but not necessarily sound quality "improvements" to the level that justify spending a lot of money on RJ-45 cables, and those who are all-in on the value of expensive, purpose-built (i.e., boutique) Ethernet cables.

Nobody here can make your decisions for you and what you read could be (and often is) very different than what you will hear in your own system. The articles and reviews I have read support a pretty wide range of solutions, including:

• improvements being gained by simply replacing your Cat 5/6/7 cables with (slightly more expensive) Cat 8 cables,
• further improvements resulting from a range of lower to mid-priced network cables ranging from the relatively inexpensive Supra CAT8 Ethernet Cable or Viablue EP-7 CAT6A Network Cable, to the mid-priced Wireworld Starlight Cat8 Ethernet Cable, to something a bit more expensive like the SOtM dCBL-CAT7 Audiophile Ethernet Cable, and then
• the need to spend money on relatively expensive, esoteric network cabling to get the most from your digital gear, such as the over $1K J- CAT Ethernet Cable or the uber-expensive AudioQuest Diamond RJ/E Ethernet cable.

So, you asked for some links. Here you go. The first link includes a discussion of "blind" testing the author conducted. The other links are mostly reviews of the cables mentioned above.

http://www.audiodrom.net/en/special-edition-reviews/104-ethernet-rj-45-cables-shootout

https://hifiwigwam.com/forum/topic/132474-throw-away-your-ethernet-cables-and-audition-some-cat8-ethernet-cables/

https://audiobacon.net/2017/05/31/supra-cat8-ethernet-cable-review-an-amazing-spotify-and-tidal-experience/

https://www.audiostream.com/content/wireworld-starlight-cat8-ethernet-cable

https://audiobacon.net/2017/03/16/sotm-dcbl-cat7-review/

https://audiobacon.net/2019/12/06/jcats-1100-ethernet-cable-now-with-gold-connectors/

https://parttimeaudiophile.com/2015/07/24/audioquest-diamond-vodka-and-cinnamon-ethernet-cables/

http://www.the-ear.net/review-hardware/audioquest-ethernet-cables-pt2-ethernet-cable

https://arstechnica.com/staff/2015/02/to-the-audiophile-this-10000-ethernet-cable-apparently-makes-sense/

ecolnago,

I agree with you, it shouldn't matter, but it does...
Heck just try a ISO Gen and it improves even more.

ozzy

mike_in_nc
There is considerable divergence of opinion on the value of boutique cables when used for USB or Ethernet transmission. Some think they are vital, others find that the extra expense contributes little or nothing. So, I would expect the answers you receive to reflect that divergence.

>>>>You might be able to make the exact same argument for almost any debate regarding cables or power cords these days. But you have to ask yourself, why would someone like AudioQuest go through all the trouble of controlling directionality of their Ethernet cables and digital cables if the signal being transmitted was 1s and 0s? You have to ask yourself why would anyone do that? 😬 If it is some wild marketing ploy here must be easier marketing ploys.

I haven't dabbled in boutique ethernet cables but I will say you can get a nicer than standard cable with better shielding, metal connectors, and faster transmission for very little money. That's the route I went with a upgraded Cat8 cable. I won't claim it improved sound but I was chasing noise issues and wanted to better shielding.

Just read through this thread to see the diversity of views.
https://forum.audiogon.com/discussions/difference-in-sound-between-copper-and-silver-digital-cables?highlight=silver%2Bcopper%2Bdigital

There is considerable divergence of opinion on the value of boutique cables when used for USB or Ethernet transmission. Some think they are vital, others find that the extra expense contributes little or nothing. So, I would expect the answers you receive to reflect that divergence.

Then perhaps this is central to my lack of understanding. Are not the electromagnetic waves by which the data is being transferred thru the cables between the router/streamer and streamer/DAC purely digital (packets of ones and zeros) in form?

Nothing should be analog until the Digital Analog Convertor converts it, right? Or am I not understanding this (or it's implications) correctly?
Todd

Digital cables and Ethernet cables are no different from any other cables that transfer electromagnetic waves. It’s not as if those cables are passing packets of ones and zeros. That’s why consideration must be given to the same parameters as any speaker or power cord in terms of honoring the inherent directionality of wire and the dielectric material, purity of the metal, purity of connectors, etc.