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I am wondering how jitter manifests itself in CD playback - is it excessive "s-s-s-s" or anything else?
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Tutorial on what Jitter is.
~~~
Our lunacies may be indulged a while longer
Depends on the spectrum of the jitter and of course, the amplitude.
It cause veils, haziness, echoes, bass fatness,out of focus, like looking out a dirty window or all of the above.
Its the #1 issue with digital audio, both CD amd computer.
Steve N.
Can't be in both places at once.However with advancements in Science and Quantum Computers Jitter may be a thing of the past.
In about 20-40 years when the cost has come down enough Quantum Computers in our gear will be able to present all data to all relevant points at the exact same time.
Good News Is:
Better sound is on the horizon.Bad News Is:
I will either be deaf or dead or both when it happens.
Dynobots Audio
Music is the Bridge between Heaven and Earth - 音楽は天国と地球のかけ橋
Edits: 06/03/12
Jitter can be slain by the right protocol and interface. As it stands, the vast resources of the electronics industry are not pointed towards this issue, so it is left to a relatively small community that is interested.
"Knowledge is knowing that a tomato is a fruit. Wisdom is knowing not to put it in a fruit salad"
> > > > > Jitter can be slain by the right protocol and interface.
Sure in terms of audibility jitter is really a non-issue esp with today's gear.
But-----technically jitter will always be around. Even if data is asynch etc. there are plenty of other variables that can cause jitter.
BTW, now that you have stepped up to a different league in Dacs what are you planning to use for a source thats in the same league as your Berkley Dac?
Dynobots Audio
Music is the Bridge between Heaven and Earth - 音楽は天国と地球のかけ橋
"BTW, now that you have stepped up to a different league in Dacs what are you planning to use for a source thats in the same league as your Berkley Dac?"
I am not sure what you are talking about?
I am using a Squeezebox touch to feed the SPDIF of the DAC. I have a SOnos systrem for the TOSLINK. THe AES/EBU - I haven;t decided that one yet.
I wasn't happy with the Asynchronous USB because you can't really put anything else on the bus without affecting the sound negatively. Also I didn't like that if things are running in the background or another process may start to hog things which causes a major degradation in sound quality as well ... I know firewire is potentially a better solution to this - but it seems to be fading somewhat, not gaining in popularity (probably due to the inexpensiveness of USB)
"Knowledge is knowing that a tomato is a fruit. Wisdom is knowing not to put it in a fruit salad"
For good CD playback, one must be able to sit still for a while, so one espresso is enough.
- - - If you cannot measure it, how do you know that you've reduced it, and how would you know if it was jitter in the first place that was causing your music to sound less than ideal?
IME there are no definitive ways to characterize jitter, becquse it has both qnd amplitude and spectrum component. The entire jitter spectrum must be examined, and even then the correlation to SQ has not been established.
So what you are saying is there are no clear definitions of what "jitter" actually is. Apparently jitter is a highly complex issue, or set of issues. One needs to examine all the facets of jitter, but even if one does that, there is no established correlation between jitter and sound quality.Wait, what?
All these audiophile vaporings and hyperventilating over jitter and no one has established a correlation between it and sound quality? Up above you ascribe all sorts of ills to jitter, but apparently none of them have been established as correlating to jitter? If there is no established correlation then how do you know jitter is causing the ills you complain of?
Edits: 06/04/12
As you know this Jitter Monster is as elusive as Big Foot.Nobody can get a good conclusive image of the Beast so they claim every turd in the forest belongs to it.
Dynobots Audio
Music is the Bridge between Heaven and Earth - 音楽は天国と地球のかけ橋
Edits: 06/05/12
I built a very inexpensive PLL circuit with the same high quality VCXO I used in my DAC. The input is attached to the clock to be measured, and the correction signal to the VCXO is bandpass filtered and then amplified, and I use the math and averaging functions on my storage scope for display. It's very sensitive, but not calibrated. I just use it as a "sniffer" type device and for comparison measurements. My main priority was getting visibility on very low amounts of data-correlated jitter, so I use it with a test CD, usually something with a worst case type signal for PCM induced jitter, such as the low level -90dB sine wave on most discs. This is the same type of method Stereophile and others used in the early days before switching to the analog sideband method. I believe there was even a construction article on a calibrated version in one of the DIY magazines way back then in the mid 90s. They all use the same general topology of extracting the correction signal, which will be mostly the jitter on the clock being measured.
Have you been able to 'see' the differences in jitter between say two different DACs under test? Were you able to make any correlation in the amount of jitter vs audio quality? How much jitter is necessary to definitively hear a difference?
I wonder if there's a way to deliberately increase or decrease jitter in real time while listening for changes in audio quality.
"I wonder if there's a way to deliberately increase or decrease jitter in real time while listening for changes in audio quality."
Now you're talking! Especially on the increase end of the knob...
I don't know if data correlated jitter is especially audible or merely a common problem. I need to re-read Dunn's paper, it's been many years. But as an approach to understanding systems, making things worse is more often than not an easier way to get a handle on what's going on than making them better. And it's a lot more accessible to us hobbyists since the only piece of exotic test equipment we need is already mounted to our necks.
Perhaps the sweetest thing about making things worse is that there is virtually no upper limit while at the other end we can only asymptotically approach perfection. Let's do it, let's make our stereos sound worse this very day!
And learn something...
Regards, Rick
..How do I deliberately and continuously increase jitter in real time while listening for changes? I like your idea of a 'jitter knob'. ;-)
So ya want MORE jitter do ya? Yea! How much can you take?
I suppose you could modulate the feed from the PLL to the oscillator, you could even filter it with the inverse of the PLL Fn to give you a direct dF/V even with the PLL fighting you at LF.
Might be fun to rig up a devilish digital dirt road. A cable that can slew rate limit the signal and run it through a comparator whose threshold you wily wiggle. The D^3 R, invented by Rick, not Al Gore...
Rick
So don't leave us hanging! Tell us more about this gadget of yours! How well does it work? What have you learned from it? Are there any links showing how to make one?
Inquiring Minds want to know!
.
My take is that it is when digital sounds hard. Some notes might be shrill, some just don't seem right. Listiner fatigue usually sets in fast.
I throw my windows open wide and call to you across the sky.
How odd. I'd guess that the vast majority of Asylum inmates could immediately describe and identify hiss from a tape machine or hum from a ground loop or the rushing sound a stylus makes as it dances in an undulating vinyl groove. Yet when it comes to jitter, the great bugaboo of digital audio, there doesn't seem to be a clear consensus of what it sounds like or what it does.
.
Tape hiss is obvious and constant. Any time distortion (digital jitter, wow, flutter) can be perceived only as an interaction between the recording and the playback timing. This makes recognition of low level time distortion difficult and inconsistent. The situation is not unlike that with wow and flutter in LP and tape. There are some subtle tape distortions such as scrape flutter that many audiophiles won't recognize and identify unless they are at high levels.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
Ah, good point. After a little thought I see that every example I gave could be grouped under the heading of "Noise," and that jitter should be classed as "Distortion."Is this a good way of thinking about it? "Noise" is inherent to the playback chain and is always present, while "Distortion" is error created by how the signal chain handles the music itself. I'm struggling to figure out how frequency response deviations fit into that paradigm, perhaps that's why they are specified separately.
Anyhow, being constant, Noise must be far easier to recognize than Distortion, which is only present as a shading to the music itself. I guess one of the benefits of Digital is a dropping of the noise floor to levels Analog recorders are incapable of. Certainly it's easy to tell my "AAD" recordings from my "DDD" recordings simply by the presence of the tape hiss in the former. I suspect, though I don't know this for sure, that the Digital recorders also have a flatter frequency response than Analog recorders. I do know that the specifications for CD playback show a far flatter frequency response than that of any phono cartridge I've ever seen.
I'm still left wondering what "Jitter" sounds like. As it is a Distortion, I guess the question is tantamount to wondering what "Harmonic Distortion" sounds like. As you point out, the vary nature of Distortion makes it difficult to hear unless it's sufficiently high in level. I'm not sure I've ever heard Harmonic Distortion, perhaps because all the amps I've ever listened to have sufficiently competent circuits as to reduce it to the level of inaudibility. Certainly I don't sit up nights worrying about ways to reduce the Harmonic Distortion in my system!
If Jitter is just Distortion, then doesn't it follow that like any other Distortion it too could be reduced to the level of inaudibility? I guess to paraphrase the old question, "If a tree falls inaudibly, does any one care?" How soft does Jitter have to be before we can stop worrying about it? How loud does Jitter have to be before it becomes intrusive?
Edits: 06/02/12 06/02/12
Jitter is a very non-linear form of distortion, and not harmonic at all. There is also a non-linear relation with signal amplitude in PCM encoding, because there are large numbers of bits changing at different signal levels. In fact, the worst jitter often occurs around the 0 level with the PCM twos-complement encoding because all of the bits change from 0 to 1. These changing bits on the data line are easily coupled to the clock in the form of data-correlated jitter (often thought to be the worst form) because of return path impedances (among many other mechanisms).
Whoa! I think I threw out my neck watching your post go over my head!
I can't say I "read" your post, as reading supposes some sort of comprehension, but after examining it several times I conclude that Jitter, like Frequency Response, doesn't fall neatly into the category of Distortion. That is, while Jitter is a Distortion, it would be best to treat it as distinct from the types of Distortions normally associated with audio gear. For example, Jitter is not normally an issue with amplifiers.
So timing errors are distinct from other types of distortion. Fair enough. It strikes me that timing errors have always been part of audio. We just didn't call them Jitter back then. Turntables had wow, tape decks had wow and flutter. As you point out with digital Jitter, this "analog Jitter" would also be non-linear and not harmonic at all. And yet even today the golden ears would never describe analog playback as hard, or glaring, or boring and uninvolving, or if they did, they wouldn't blame analog timing errors for the problem.
What is it about digital Jitter that makes it so pernicious? I find it incredible that timing errors within a competently designed electrical circuit could be greater than timing errors created by a moving mechanical device. To the contrary, I suspect the timing errors in an electrical circuit to be much smaller than the ones in analog devices, perhaps orders of magnitude smaller. For example, it's common knowledge that even a cheap electrical watch can have greater accuracy than the nicest mechanical watches. If listeners can dismiss "analog Jitter" why are we so concerned about the much smaller "digital Jitter?" How does the digital domain turn common sense on its head so that a much smaller cause has a much larger effect?
Sorry, the definition of jitter is fairly simple, but the causes can be much more complicated to explain. Note that there is jitter always present that is somewhat analogous to the wow and flutter example, and most people may not be bothered by it, or even recognize its presence. It can be caused by ground loops, so you may have a power line frequency on the conversion clock that becomes a jitter component. Many digital components have very large amounts of low frequency jitter and users aren't bothered by it all that much. Clocks drift with temperature and power supply levels and are easily influenced by other digital and analog operations in the device (and even outside the device).
But the type of jitter I was describing as data-correlated is mostly caused by highly non-linear interactions between the data and clock while still in the digital domain, so doesn't really sound like something that happens naturally in the analog world. Maybe something like a distorted ghost of the music in the background, but also displaced in time. Music is repetitive by nature, and the repeating data bit patterns can be coupled to the conversion clock through a variety of means because the data waveform is not symmetric like a clock. Even a simple operation like transferring the data and clock from a digital filter output to the D/A convertor input can add data-correlated jitter to the clock since they share the same return, and the data bit pattern will modulate that return.
It could be audible as glare, but also as soft, diffused out of focus sound. It can also impact LF definition and speed perception. I have experienced all of these manifestations, clearly contributable to jitter. It really depends on the amount and spectra.
Jitter simply makes the music seem "less interesting"..... "Boring"........ It might be a nice performance, but the listener is left cold......
If OTOH the "jitter signature" of the original master is kept intact (which IMO is better than just eliminating jitter), the performance takes on a unique, interesting quality. The listener becomes engaged to the performance.
From another perspective, jitter makes the harmonic structures of various instruments seem "generic"..... Whereas good jitter performance enable the listener to appreciate the unique qualities and nuances of these same performers.
Do only digital masters have "jitter signature", or does it apply for all analog masters as well?If some jitter is desirable, do you mean that it is better not to reclock music? That way I can hear the jitter already on the recording?
Let's say I purchase an HRx file from Reference Recordings, where the file I download is exactly the same as the master. Should I have the lowest possible jitter front end with no reclocking then?
Edits: 06/01/12 06/02/12
"Do only digital masters have "jitter signature", or does it apply for all analog masters as well?"
It's called "wow and flutter". It gets embedded in the recording.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
Yes glare, edginess, harshness, particularly on higher amplitudes. When jitter becomes obtrusive it is hard to relax and enjoy the music. That said a lot of set ups mask the nasties of jitter so it is not so apparent. I sense a lot of audiophiles blame the speaker for the harshness - seems logical because that is where the sound comes from, but if they choose a speaker which sounds better all they are doing is suppressing the input rather than cleaning up the sound.
My mantra for years has been to concentrate on the most affordable input as the first area to upgrade. There is no escaping the GIGO principle. Sadly many of the jitter problems come from poor digital filtering, something which is a black art.
The latest and greatest here is termed "apodising" and the term has been coined by Ayre, PSAudio & Meridian although they do not all use exactly the same algorithm so buyer beware if others jump on the band wagon to use that term. The above 3 companies do have very effective digital filtering which shows up as excellent quality audio but that is not to say others have not achieved similar results with different approaches.
It has taken a few decades but IMHO audio quality via digital is now a mature product, one which is giving me better sound than I ever got from vinyl. And a lot of that has been better awareness of jitter problems and ways of avoiding them.
John
Enjoying over 9000 mostly classical CDs via Sennheiser HD800 headphones & a NuForce DAC9 on a Meridian Sooloos system.
The main 7.1 MC electrostatic speaker system is enjoyed at night for A/V
"Sadly many of the jitter problems come from poor digital filtering, something which is a black art. "
Can do, but a lot of it has little to do with the filtering - and much has to do with the clocking/timing of data which is entirely different that the filtering.
It is a difficult thing to diagnose and to fix.
But it is not a black art by any means.
"Knowledge is knowing that a tomato is a fruit. Wisdom is knowing not to put it in a fruit salad"
I think that it's glare.
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