[ROBSCIX]

First off there are many different kinds of jitter that affect various components in a digital audio system. The type usually asked about is "periodic jitter". This is basically timing errors in the master clock signal that times all of your other chips such as your DAC's, ADC,s..etc.

When you consider that a DAC is expecting a perfectly timed signal to "clock" the chip.
This clocking signal tells the DAC when to operate and convert the data.
If the signal is perfectly timed then you get a perfect representation of what was originally encoded.
However, periodic jitter is errors in this timing signal which is basically a square wave.
In a "jittery" timing signal, some pulses are too short, some are too long..this makes the DAC convert the data at the wrongs times which distorts the original information.
This distortion can also be mathematically related to the jitter.

In reality, you cannot hear this type of jitter, only the negative affect it has on the audio.
If you can think of the sound of a really cheap 80's CD player when you hear a "wow" or a "flutter" in the audio that is usually the affect of periodic jitter on the converter.
This is very quick explanation just to give you an idea of the topic. This subject is one of the most widely debated subjects in digital audio.

 

[Prog Rock Man]

When I think of an early CDP I think of a dull and flat sound that lacked realism when compared to vinyl. So, if you remove jitter does it improve the SQ? Or is it a case that removing jitter will remove the occassional 'odd' sound?

 

[atothex]

Quote:

Originally Posted by Prog Rock Man /img/forum/go_quote.gif When I think of an early CDP I think of a dull and flat sound that lacked realism when compared to vinyl. So, if you remove jitter does it improve the SQ? Or is it a case that removing jitter will remove the occassional 'odd' sound?

Can't remove jitter. A CD that sounds dull/flat is a poor mastering job.

I say don't worry about jitter until you have a top shelf DAC. Jitter is to DACs as cables are to analog stuff.

 

[paara]

Quote:

Originally Posted by tim3320070 /img/forum/go_quote.gif Ironically, it's the same wispy sound as dollar bills falling from your wallet...

hehehe, that is so so true...

Stop worrying about jitter.
Jitter may destroy your listening experience. Not from you hearing it, but from hearing about it.

 

[Prog Rock Man]

Quote:

Originally Posted by paara /img/forum/go_quote.gif Stop worrying about jitter. Jitter may destroy your listening experience. Not from you hearing it, but from hearing about it.

I posted this to add to my knowledge (and hopefully others) not because of any worries.

Benchmark and Naim have DACs out that make great play of their solutions to produce 'zero jitter'. From all of the replies so far my only 'worry' now is that Benchmark and Naim are bigging up an issue that is not actually an issue to create sales.

 

[audioengr]

If you want to learn something read this:

jitter

If not, then dont bother.

BTW, my USB interface and DAC were just rated "the best he has heard" by TAS reviewer Steven Stone in Feb issue. The difference is mostly reduced jitter.

Steve N.
Empirical Audio

 

[Prog Rock Man]

Quote:

Originally Posted by audioengr /img/forum/go_quote.gif If you want to learn something read this: jitter If not, then dont bother. BTW, my USB interface and DAC were just rated "the best he has heard" by TAS reviewer Steven Stone in Feb issue. The difference is mostly reduced jitter. Steve N. Empirical Audio

That is an excellent article that I had read a while back. It contains one of the very few descriptions of what jitter sound like that I have found

"Most audiophiles do not even realize that they have jitter until it is reduced. I liken it to looking through a window made of really old glass, when glass had ripples and bubbles in it. There is a spreading and distortion that widens and defocuses some images and creates an overall mild distortion. It is still obvious what is on the other side of the window, but it is not coming through with crystal clarity. Reducing (you will notice that I do not say "removing") jitter is like replacing the glass with a clean, flat piece of glazing. Things are now visible in great detail and with a "vividness" that was not there with the rippling glass. Jitter can be blamed for much of the "fatigue" that results from listening to some digital playback systems, just like it is fatiguing peering through rippled glass for any length of time"

To me that reads like posts above comparing jitter to a 1980s CDP and my comments of dull.

But the general view here is that jitter is unimportant and cannot be heard.

 

[atothex]

We talking DACs or transports? With transports, jitter is probably the main issue. That said, the digital transport part is probably less important than the conversion/output part.

Jitter matters, and it is audible, but it's only a small part of the digital source equation.

 

[Prog Rock Man]

Please describe what jitter sounds like atothex.

 

[atothex]

Might as well ask what THD sounds like... it doesn't have a sound of its own.

Edit: maybe another decent analogy is "What does bad food taste like?" Bad.

 

[Prog Rock Man]

Sorry atothex, but that makes no sense to me. Firstly, I don't know what THD is and secondly, if you cannot describe it then how do you know if you are hearing it?

 

[SP Wild]

The effect of jitter to me is very similar to switching the tone control bypass - when the controls are at zero. When dealing with expensive dacs I believe the effect is very noticeable - like removing another component from the chain. If one has never heard these differences, then I am at a loss to explain it in practical terms.

 

[atothex]

Quote:

Originally Posted by Prog Rock Man /img/forum/go_quote.gif Sorry atothex, but that makes no sense to me. Firstly, I don't know what THD is and secondly, if you cannot describe it then how do you know if you are hearing it?

THD = total harmonic distortion. Like jitter, it's always present, and you're always hearing it. If one digital transport sounds better or worse than the other, then you're most likely hearing differences in jitter. That's how you know you're hearing it.

What I'm trying to say is that jitter is not its own sound, like a hand clap or something. I really can't explain anymore beyond that...

 

[edstrelow]

I think what is being said is that there is no one single effect of jitter. It is a general degradation of signal, sometimes effecting one aspect of the sound and sometimes another.

I have seen a study which played a sine-wave with differing amounts of jitter added and you could decide for your self what the jitter did and when it was obvious. However this still misses the point that jitter may have a different effect on another aspect of sound or even a different frequency sine wave.

The suggestion that you compare cdp's or dac's of different vintage may be helpful. Having gone through several generations of such devices I would say I am getting less harshness, more ambience, and mre realism, maybe even a more analog sound. Some of this is presumably related to jitter.

As far as getting good sound you really need to get around and hear various systems at friends or at a Canjam. You will find out that there are differences that matter regarding the sound of different equipment. But don't expect this to be closely related to measured performance of a specific parameter such as jitter. Probably but not certainly. But that is how you will find out how far you are from the current state of the art re: auditory perfection.

 

[Prog Rock Man]

Again, thanks for the responses. It does seem to me that differences that are being attributed to jitter may not be jitter. They may be the differences you would expect between different products for a whole host of reasons, jitter being one of course.

Is there a product or test example where say a DAC has been fed a signal with low jitter and then one with very high jitter to see if a difference could be heard? That would seem to me to be a conclusive test.