What does jitter sound like?

[cfmsp]

 

"Now, in a studio environment, and it's important to note that this is an educated guess, I suppose further reduction of jitter may be important because jitter, like all noise in recording would tend to multiply with the multiple stages of recording and production. At home, you're converting a digital signal to an analog one once."

 

Tim,

It's my understanding that jitter is only relevant (evident?) when digital signals are converted to analog.

IOW, when mastering, files are processed digitally and do not accumulate jitter in the manner that I believe you were suggesting.

 

I read this in Mastering Audio, by Bob Katz, who does believe that jitter is audible, or so he says in his book and several articles posted at his site digido.com

 

http://www.digido.com/faq/10-J/64.html

 

http://www.digido.com/index.php?option=com_content&view=article&id=15:jitter&catid=13:bob-katz&Itemid=90

 

clay

 

 

 

 

[Roseval]

It's my understanding that jitter is only relevant (evident?) when digital signals are converted to analog.

IOW, when mastering, files are processed digitally and do not accumulate jitter in the manner that I believe you were suggesting.

 

PCM audio is a fixed word length at a fixed sample rate.

So there are two stages where jitter matters: A/D conversion and D/A conversion.

Between these stages everything is digital. In the digital domain you are processing bits just like when you are manipulating any other file.

Katz is right, this won't add any jitter.

 

BTW: if DavidJPettifor adds to the end of his post we probably get rid of the italics

 

[mpmct]

 

Katz comments in this thread, a few weeks ago ...

 

http://www.gearslutz.com/board/mastering-forum/351604-amount-jitter-makes-sound-worse-4.html

 

 

[cfmsp]

 

thanks mpmct

 

quite an interesting thread you posted.

 

enjoy

clay

 

 

[tfarney]

Did Katz say he thought jitter was audible? I'm not sure he committed, but it sure didn't sound like he thought it was a problem. No matter. The bottom line for me is either I can't hear it or what I hear is not getting in the way. My best recordings sound smooth, natural (for recordings) and precise. Drums and bass attack with authority and resonate with nuance. When cymbals are played, they don't sound like splash and hash, but like the timber and ring of individual instruments. When an audience applauds, I don't hear a rain stick, but the varied sounds of hands clapping. The sibilance I hear is the sibilance of human mouths, not sloppy reproduction. My sound stage is wide and deep and open, and the instruments are placed individually. And my God it is fun.

 

The distortion of these things are what I have heard attributed to jitter and I don't hear a problem. I will turn my attention elsewhere. Turn yours where you may.

 

Tim

 

[DavidJPettifor]

Roseval wrote:

BTW: if DavidJPettifor adds to the end of his post we probably get rid of the italics

 

?

 

--

djp

 

[PeterSt]

Tried to get it out, but somehow won't work.

 

Stupid thing.

Can't remove my post either, I think.

 

So apparently the poster where it started to go wrong must add a [/cite] (with proper carets) to his post.

Here it doesn't work anymore.

 

 

[drdigital]

So Steve, you were design lead on Pentium2, shame your hyperlinks to your many patents don't work!

 

I will have to take a close look at my old P2 PC, I didn't think there was any valves in it but I might be mistaken!

 

[DavidJPettifor]

So apparently the poster where it started to go wrong must add a [/cite] (with proper carets) to his post.

 

Ah! My bad! Apologies to you, Roseval et al. I shall endeavour to go back and sort out any posts I've made that have omitted the . Very slack on my behalf.

 

I shall move myself to the back of the class, face the wall and place a pointy hat with the letter "D" on my head. When at school I always thought that "D" represented the initial of my first name!

 

--

djp

 

[DavidJPettifor]

Tog wrote:

Whilst I'm at it I don't believe in Father Christmas, hedge funds or tube amps but thats my problem.

 

Don't believe in Father Christmas?! Don't believe in tube amps?! Ahhhggg!!!

 

I'm with you on hedge funds though...

 

--

djp

 

[PeterSt]

As all so often it seems very necessary for people to "state" that when they can't hear whatever it is, it is not there. Isn't this odd ? It would *never* slip into my mind that when I don't hear something my co-listener does, to blame *his* ears and say something "hey, you, your brains, your ears or even your d*ck is making it up !".

 

Come on now. Even if Bob Katz doesn't hear a difference it just means it is him not being able to for whatever reasons. Bad youth perhaps.

I only want to say : Nobody should take notice of those who DON'T hear. I truly wonder what is the use of this over and over stating "I can't hear such and so". It's a waste of space IMO, and by now all over this forum.

 

Yes, when everything has cooled down in this thread, I start ranting again. Why ?

Because I so much feel the frustration of Steve N.

So, do I write this to symphatize with him ? maybe, or maybe a bit at least. But the main point is that you deaf don't allow the others to proceed. To proceed along the few (yes a few) on this globe that give their life to proceeding on music playback through loudspeakers.

 

Someone like Steve N. hangs around here a. to sell something, b. to explain about stuff you guys are asking questions about. But wait a minute, did I have the sequence right ? I dare say no. So again :

a. to explain about stuff you guys are asking questions about and b. to sell to those who believe that quite some knowlege is behind those outlays and further text written.

 

It is completely outrageous that someone has to come up with his credentials to more or less prove the good will including some knowledgde to really do it in practice. And just because of that this is so outrageous it is also a last step not knowing of anything else anymore.

But the deaf *are* helpless. In audio they are. This is almost just math.

 

Right. So now you can all shoot at me. I already see it coming.

"Hey, well done T. ... I'm all with you !" or the other wat around if you know what I mean.

 

I gave up in here. There is no single thread -interesting by itself- that ends up in the exact same dead end, only because one or two claim not being able to hear the whatever it is about. Then as a last resort the by now known twist of "hey, but it is about the music !" comes up again, and 100 people agree with the A's and the T's and everybody is happy again. Yeah, well, an intelligent way to kill each and every thread in here.

 

I have never been banned anywhere so far, but if one place is the first, it will be this one. I will be banned, because again each and every thread that ends up with all the kitty stuff and zero worth, really ends by me talking about it. YOU GUYS DESTROY. You destroy the goodwill of some who want to spend their time on explaining how things really are, and to me it is the most outrageous to counteract that by saying "nah, he wants to sell his stuff only". And even then, so what ? I spend my life on improving audio, and you know, I do that for you. With or without patents. That is why I recognize so well what is actually happening here. Guys like Steve will disappear. I gave up anyway ...

 

But hey, I always think that a rant has to along with some constructive signs as well. So here is one :

 

How does jitter sound ?

 

Although many many characteristics apply at little changes of jitter, there is one nice comparison I coincidentally own myself, and which indeed allows for such a comparison :

 

I have this DAC which accepts SPDIF and I2S. Both connections can be fed from the same soundcard, and a PC is the source in either case;

The DAC can be put into a mode with some 3ps of jitter, where reclocking takes place behind the SRC. It can also be set to a mode where the net jitter is fully dependend on the incoming stream and the jitter that comes along. For SPDIF this is kind of huge, and for I2S this is, well, enormeously less. Keep in mind, both streams are "bit perfect";

 

The difference is so huge that you can well speak of two different DACs;

The very jittery SPDIF connection sounds relatively "rough". Not bad or anything, but the character is one which can be desribed as rough.

The I2S connection can be characterized as plain sweet. I don't think there is a better description for it. Just "sweet".

 

Since I built this DAC myself (NOS 24/192 with or without filter or OS 24/192 through the SRC) I know what is going on and what to expect from it. I can measure it and I can see what I hear. For example, the downsides of NOS are visible as well as audible, but the upsides are just the same. This difference between NOS and OS is huge by itself, but nothing beats the difference between high and low jitter.

 

One can be deaf and still perceive the difference. The point is though, who is able to actually listen to one and the same DAC with one and the same source, and feed it with relatively much jitter, as well as much less ? I dare say, nobody, unless you are in laboratory test conditions, and then still. The chance that such a laboratory environment uses an I2S connection from a computer source against SPDIF are plain zero already, let alone that the DAC concerned allows the choice of the inherent jittery connection in front of the SRC.

 

Besides that, who is so stupid to create a setup like I did ? only me of course. And why ? because it is me who states that jitter can be influenced by software which obviously doesn't work hence can't be proven when the DAC is inherently immune to incoming jitter.

 

In the end the technical and audible differences can be proven by endless experimenting; These days I am working on proving the technical differences on measuring through the player software. The audible differences were clear long ago, but especially to an engineer it is nice to *see* the differences. And what exactly they are. I will be presenting my measurements, and you can bet that I don't do that for myself. How the desease is called that I do this for "you" I don't know, but I guess some people like to show their credentials or in other words, their contribution to this world full of mystiques.

I, nor anyone else in audio I think, need satisfaction or honours from anyone. Sharing is the keyword here, and any audiophile who wants to keep his findings for himself is merely a lunatic.

 

Anyone who attacks such sharing by whatever means of arguments, is, well, just deaf. And holding back progress. Those who applaud that, don't want progress.

 

Now, mark this as the most stupid post ever. :-)

Probably half of it doesn't come through as intended because of my english, which always is a problem when emotions are in order.

 

[BobH]

I agree.

 

[Roseval]

The DAC can be put into a mode with some 3ps of jitter, where reclocking takes place behind the SRC.

 

If you put on the reclocker, is there any difference between SPDIF (high jitter) and I2S (low) or does the reclocker eliminates any input jitter?

 

[DavidJPettifor]

"Calm down dear...

 

 

 

it's only a forum!"

 

This will probably mean absolutely nothing to anyone outside the UK.

 

--

djp

 

[shenzi]

I don't think anyone claimed that it's not possible to hear jitter when it's present, just that modern DACs have reduced it to a level where it isn't worth worrying about. So the most basic tweak would seem to be to bin the inadequate DACs.

 

[DavidJPettifor]

Yes in all seriousness, I think the one thing I've garnered from this thread is that everyone accepts the presence of jitter but most agree that it just isn't audible. I've read through quite of few forums, similar to this to discover what others think. It appears that the arguments pretty much start and end the same as here.

 

To a layman, like myself, if I'd heard something, I would query what I was hearing by describing the sound I'd heard. What I can't grasp is how by trying to address something that can't be heard, this will somehow improve the sound of my music?

 

--

djp

 

[Ashley James]

PETER

 

I think if you re read what has been written, you may find that you've misunderstood what has been said.

 

However I'd also point out that the argument for hearing what can't be measured is specious. The fact is that modern measuring equipment can actually measure to the thermal noise in copper wire, whereas when ears are tested, they don't measure consistently.

 

Consider an experiment where a piece of equipment is set up for a listening test, having first been measured, but this time we measure the listener's ears as well. Auditioning takes place and observations are made. Now we change a USB cable or something that won't measure differently and we measure again to be sure. After the audition we measure the listener's ears again. What we find is that whilst the equipment measurements remain the same, the hearing test results for the listener will have changed.

 

Anybody can book themselves in for five consecutive hearing tests on five consecutive days and be almost certain to get a different result each day. Therefore the sensible conclusion to the experiment is that the equipment hasn't changed but our ears have. An audiophile will conclude that our ears have revealed what the test equipment cannot!

 

Ash

 

PS. Shenzi has it in a nutshell!

 

[PeterSt]

Roseval,

 

I must be honest here, for several reasons I can't explain my answer, which btw is Yes. So :

 

a. It is commonly known that no matter how, reclocking behind the SRC is very good for jitter specs, incoming jitter will siple through to some extend;

 

b. My audio measuring equipment does not have a clock (and output) for I2S, so I can't measure this myself. I must depend on the specs here.

 

c. Right now I am working on some means to overcome b. which means measuring through the software, which implies making up your own means of measuring *and* interpreting. This is not easy. Or at least not for me, right now.

 

d. Number c. is already necessary because the software influences jitter just the same. Ok, says me and for me to prove anyway.

 

Back to the answer of "Yes, there is still a significant difference" there seems to be more to it. The specs may be wrong (though the principle would be right and fit the specs), or possibly the SPDIF connection is just way out of "specs" that everything behind it is destroyed. Btw, I measure 1ns at SPDIF (compared with analogue out) which of course is way much, but I don't think the interpretation is correct.

 

On a side note, it is rather difficult (or needs the experience) to interpret the audible differences as well as measured differences correctly. This starts with the diffence between OS and NOS which -as said- is huge by itself. And since the SRC will imply oversampling things become apples and oranges quickly at comparing incoming jitter through the SRC. An example :

 

Suppose heavy oversampling (which this DAC does not, but anyway), then feeding it with a square at 10KHz will end up with a pure sine. You probably know it. Now, if someone could tell me how to interpret jitter results (at measuring analogue out !) when a pure square has become a pure sine ... I'd be glad to learn.

So, the only way to do this properly IMO, is to not oversample the lot, and compare that. Right, but now there's harmonic distortion all over (which is so called not there when a square becomes a sine).

Next, there's the necessary filtering and so far I refuse to believe that any measurement after this filtering is able to present reliable results. From this comes (theoretically anyway) filtering in the software (not FIR), and while the player plays including the filter, I think there's a better chance of reliable measurement if the measurment equipment could only hook into the hdd where the (filtered) source is. Well, personally I am not ready for that yet. -

 

Quite another subject, though very much related, is that I found that the mains contains noise which is immunized by the DAC, but which is sure not by the measurement equipment. This noise is inaudible and evenly throughout the audible spectrum looking as white noise, and can be captured by a microphone. Yes, I said inaudible. :-))

 

I am convinced that there is much more to it in general, and that measurements say nothing without the proper interpretation. Somehow I never see this interpretation, and only the elementary means of how to measure what. For example : I never saw anyone write about a sigma-delta DAC putting out complete distorted square waves at 3KHz already, stating a THD+N of 0.0001% at the same time.

So I guess I am going to do it. At least I set my mind to it because IMHO this is a big fraud *or* is about professionals not knowing how/when/what to measure. But hey, who is a fraud at using AES17 standards ?

And if one tends to not agree with that standards and the means of measuring, who is even able to setup new test means ? not many I guess. Not me right now anyway, but I guess I am going to do it.

 

[Roseval]

What I can't grasp is how by trying to address something that can't be heard, this will somehow improve the sound of my music?

 

There is nothing to crasp.

Some say it is A

Some say it is not A

Then a third one chimes in and say that A or not A is utterly irrelevant because it is B.

 

Where it all amount to: if you want to improve the sound quality, would you benefit by buying a better DAC?

If all these well designed modern DACs sound the same, it is easy. Just get your self this well designed modern DAC and of course, take the cheapest one. Why pay more for zero difference?

 

Let try

Cambridge Audio DacMagic $399 (2008)

Bel Canto e.One DAC3 $2495 (2008)

Modern enough?

Now if you don't hear any difference between the two, be glad, you saved $2000,-

If you do hear a difference, be glad, your equipment is capable of resolving subtle differences.

 

 

[Ashley James]

All DACs have residual RF on their outputs that can be shown to affect some amplifiers badly, so why focus on jitter.

Price is no indication of performance because the parts cost a few pounds maximum, which is why I suggested that you start with an M-Audio Transit as a reference. It's £50. Pro Audio DACs are far cheaper and often better because they are made in enormous quantities by bigger companies who can afford better engineers.

 

The Cambridge Audio 840CD is better than the Dac Magic, in fact it is about as good as DACs get and comes with a CD player, so that's where I'd spend the money.

 

Ash

 

There are bigger problems in the rest of your system.

 

[BobH]

Quote : All DACs have residual RF on their outputs that can be shown to affect some amplifiers badly, so why focus on jitter.

 

This is why the good people at Cambridge Audio, the makers of your recommended 840CD, think you should :

 

Jitter is one of the worst quality degrading factors in digital audio playback (or recording) system. Jitter is a variation in the clock period around a central period value. It can be considered as noise on the audio clock. It is capital in order to get a good Digital to Analog (playback) or Analog to Digital (recording) conversion, that jitter be minimized.

 

Digital audio is often conveyed from one unit to the other using an SPDIF or AES/EBU link. These links use bi-phase modulation to convey both data and clocks in a single data stream. At the receiving end, a digital audio receiver (which is basically a PLL) locks to the incoming data stream and extracts clocks and audio data into separate physical lines. Of course, if the transmission is of poor quality, jitter will be introduced. The receiver will do its best to lock the PLL to the incoming stream but depending on the amount of jitter present, there will still be some jitter at the output of the digital audio receiver, which will be of bad influence on audio quality.

 

They then go on, obviously, to explain why their system for correcting this audio horror is better than anyone else's. They then couple this wonderful new technology with their 'Q5 Upsampling' to bring about even more sonic benefits. The results can be read here: http://www.anagramtech.com/technology/q5-upsampling/ . All in all they seem to have gone to extraordinary lengths on our behalf, to make sure that we do not need, as your rightly point out, to worry about such things.

 

So, I think we can agree that jitter needs to be addressed and is, indeed, being addressed to the point that most people do not need to worry about it.

 

So, now then, what are your objections to the topic being discussed, so that those interested forum members may understand it better? I make the assumption that you would rather not have it discussed on the basis of your many posts repeatedly telling us that it doesn't matter. Why do you want the forum to be largely uninformed about digital jitter and its effects and solutions? If you're trying to save me from unnecessary worry, there really is no need - I can cope.

 

Quote : Pro Audio DACs are far cheaper and often better because they are made in enormous quantities by bigger companies who can afford better engineers. You may like to re-think that!

 

[Ashley James]

Bob

 

Cambridge Audio stuff is superb and for that matter Dan Lavry's DAC has just come out top in a comparative review in Hi Fi Choice, so these are good engineers doing the job right and producing good DACS.

 

Now if I was a manufacturer reading this (and I am) and I wanted to re-assure audiophiles about something that I knew instils paranoia in them, I'd write a few thousand words or maybe the Ad copy writer did on Jitter.

 

As I said before with my "enthusiast talking to friends" hat on, I'd tell you that jitter was just one of many factors to be considered when designing a DAC, that for some time now they've been largely immune to jitter, that more recently the receiver chips have improved things further, so that it is no longer and issue, but and it is a big but, if you have an older design of amplifier with high HF distortion, it may be susceptible to RF that they produce.

 

What could be fairer than that?

 

From AVI's perspective we also were aware of the problem (audiophile neurosis), so we eliminated it completely but didn't shout from the rooftops. We understood and dealt with it and chose to re-assure people rather than add fuel to the fire that is this jitterthon.

 

I'm beginning to think Elvis lives too.

 

Ash

 

[tfarney]

"I'm beginning to think Elvis lives too."

 

Thankyouverymuch.

 

BigE

 

 

 

[Purite Audio]

Ash you must really must make more of this in your advertising, I don't believe anyone else in the world has 'completely eliminated jitter'!

 

[BobH]

Yep, nothing inherently unfair about that, all very reasonable. I'd be a bit picky about the 'neurosis' bit and describe myself as inquisitive - but apart form that we're AOK.

 

So, if I want to be inquisitive about jitter, its effects, audibility and solutions why do I need to be reading 1 interesting thread interspersed with a dozen on why it doesn't matter? To be honest, I agree with most of what you say about its ultimate importance in the scheme of things but I would like to hear a bit more from the other side, as it were. That's me being inquisitive again.

 

So, is this not the right forum for such discussions?

 

That is most definitely the impression I am beginning to get. It is self-evident from this thread, and its very great persistence, that those for whom jitter is not an issue are unwilling to simply leave it be and do something else. It has become mandatory for every on-topic comment to be immediately met with either derision, flippancy or, albeit well meant, yet another categorical rebuttal of its importance.

 

BTW - did you find that number for the Samaritans?