what is jitter supposed to sound like?

The Stereophile CD is a good idea. If you want a verbal description from someone who has battled it a bunch, I would say that it makes everything less distinct. It removes the fine details that create depth cues and the quick, high frequency transients that make percussive and plucked instruments sound real and exiting.

Sounds loke something that you have never heard before! If you could hear it, it would sound like a low level hiss.
More important, how would the recording sound without dither? How can one know, since dither is always used as standard.
Bob P.

I think jitter sounds like the jingle of loads of money in audiophile manufacturers pockets for expensive products. The marketeers love the sound of "jittery" and fearful audiophiles who come forth, wallet in hand, with a concern that they have some intractable and immeasurable jitter problem with their system. (immeasurable problems are immeasurably hard and expensive to fix!)

Depending on which "experts" you believe it is either still a problem today or it is something that was caused by poor clock design circuits (or sharing of clocks) in the distant past of digital circuit designs like the early CD.

In theory over sampling is meant to drive jitter problems well outside the audible band where it can be filtered out. Also, accurately clocking things out using a buffer with a dedicated and accurate clock is cheap and is known to minimize jitter.

In theory it can sound pretty much like any other noise or distortion ....as the jitter creates low level frequencies that were not in the original signal. The problem is exacerbatted if jitter is significant and repetitive (as opposed to random) and therefore correlates to a specifc noise signal rather than whiteband noise. This should not normally be the case with most recent designs, even low cost ones.

This is what Bob Katz has to say on what it sounds like;

Here are some audible symptoms of jitter that allow us to determine that one source sounds "better" than another with a reasonable degree of scientific backing:

It is well known that jitter degrades stereo image, separation, depth, ambience, dynamic range.

Therefore, when during a listening comparison, comparing source A versus source B (and both have already been proved to be identical bitwise):

The source which exhibits greater stereo ambience and depth is the "better" one.

The source which exhibits more apparent dynamic range is the "better" one.

The source which is less edgy on the high end (most obvious sonic signature of signal correlated jitter) is the "better" one.

http://www.digido.com/portal/pmodule_id=11/pmdmode=fullscreen/pageadder_page_id=52/

Opps, I confused 'jitter' with 'dither'! Definitely not the same and of course my comments on 'dither' don't apply here for 'jitter'. My bad!
Bob P.

there is some misinformation in one of the posts above:-

>> Depending on which "experts" you believe it is either
>> still a problem today or ....
yes, it still remains a problem today esp. in inexpensive CDPs & DVD players of which there are plenty in the market.

>> it is something that was caused by poor clock design
>> circuits (or sharing of clocks) in the distant past of
>> digital circuit designs like the early CD.
yes, it was caused by poor clock design (one of the reasons was using a high variable xtal for the clock source to keep BOM cost down) in CDPs of yester years. It remains an issue (maybe to a lesser degree) today.

>> In theory over sampling is meant to drive jitter
>> problems well outside the audible band where it can be
>> filtered out.
this is clearly not right! You seemed to be on the correct track citing clock designs & then ........... where did you pull out over-sampling to alleviate jitter?
Over-sampling was introduced to reduce the analog filtering requirements post-DAC.

>> Also, accurately clocking things out using a buffer
>> with a dedicated and accurate clock is cheap....
well not cheap enough for Magnavox ($35 at Walmart) or CyberHome ($38 at BestBuy) to put a highly accurate clock in these DVD player models!
Cheap is a relative term - you'll probably find a good quality clock in some "ES" Sony model & other models costing several 100 dollars. So, yes, if you are one to consider a $600-$1200 DVD or CD player to be cheap, you have a higher probability of being correct.

>> ....as the jitter creates low level frequencies that
>> were not in the original signal.
by low level, I assume you mean "low amplitude"?
Jitter raises the overall noise floor of the instrument thereby masking lower level details.

>> The problem is exacerbatted if jitter is significant
>> and repetitive (as opposed to random)
since we are talking audio here where the jitter issues are almost always clock related, jitter in audio is always repetitive. It is described as periodic jitter or cycle-cycle jitter. It is quantified as RMS jitter or peak-peak jitter.

>> This should not normally be the case with most recent
>> designs, even low cost ones.
How very mistaken are you!!

I personally do not think that there is a "sound" to jitter per se. Maybe there is but I have never heard it. What I've heard is its manifestation: loss of low-level details, reduced D.R. - music loses its snap, imaging not being precise, high freq being edgy/sharp/brittle.

"I would say that it makes everything less distinct"

That's the best description, and matches my experience. And it's a problem in both low and mid priced equipment. In low cost it's a problem due to low price components, and in mid priced equipment due to poor or careless design (a great design can be ruined if the PCB is incorrectly laid out).

Bombaywalla,

Thanks, I stand corrected. Oversampling does NOT help drive jitter outside the audible range (I was definitely confused there).

I believe, at most, oversampling or upsampling can reduce jitter wideband noise effects by the factor of over or upsampling. Also provided the output clock is not synchonized to the input clock...you can get further jitter benefits from a good upsampling circuit.

I agree with your definition of low cost...definitely Walmart is not where I would start for an audiophile system. I meant that you don't necessarily have to spend several thousands of $ to avoid jitter problems these days. Your clarifications helped.

I could be wrong..but the power supplies and analog outputs in a player or DAC seem to make the largest impact in the sound. I agree that the jitter reduction does increase the focus of the soundstage. Better analog outputs and power supplies seem to reduce the grain and edginess associated with some players. This also increases the dynamic contrast between softer and louder passages in the music. Blurring is also reduced by a combination of the three IME. Killing as much noise as possible between the power supply and the rest of the unit seems to increase the focus of the soundstage as well.

I found this article on Jitter.

http://www.regonaudio.com/Jitter.html

REG describes the sound as an audible roughness in the case of the Stereophile test CD No 2. (Pure 11 Khz tone with excessive and specific jitter added, which created sideband noise smack in the middle of the most sensitive part of the hearing range...probably a worst case scenario)

Gmood1, you are definitely on to something. One effect of power supply noise and ripple is that it changes the threshold at which digital gates switch. This can have the effect of advancing or delaying a digital transition and thereby increasing jitter.

Jlambrick, Gmood1,
it is indeed correct to say that improvement in the digital & analog power supplies improves the sound. The less ripple there is in the power supplies & the better their ability to supply current helps in minimizing the perturbations to the electronics.

yet another effect that exacerbates jitter-like effects is the transport-DAC interconnect cable (when using separates). Most cables, I believe, are improperly terminated & result in reflections. This has some of the same effects as jitter - smearing the overall presentation.

the reason I said that I've not heard the sound of jitter is 'cuz poorly designed power supplies show up as nearly the same effects I stated above (music loses its snap, imaging not being precise, high freq being edgy/sharp/brittle) as the effects of jitter!
So, when one hears loss of low level details or poor imaging or sharp highs which effect is to be blamed? Excessive jitter or poor power supplies (or poor implentation) or improper interconnect length & terminations?
I have found it hard to separate the 2 issues, in general. I can probably zero-in for my particular CDP as I know which mods have/have not been done. However, when I audition a piece at a dealer or a show or at a friend's house I don't have such detailed info.
It's a toughfy for me as I find it hard to be conclusive: "this is excessive jitter!"

Bombaywalla, good point. I found that jitter was the problem in my system accidentally. I was building my first system in 20 years and everything was new (to me). I tried everything I could think of but the sound still seemed dull and lifeless. In desperation, I thought I would see what equalization might accomplish so I borrowed a dbx Quantum mastering processor. While it was still in bypass, the sound snapped into focus like I'd never heard before. I finally figured out that it was the huge reduction in jitter that caused the improvement. I've found a much more cost effective way of creating a low jitter signal now but the symptoms I was hearing could have come from a multitude of sources.