[BrianM]

As usual, it would be fun to learn how many people could actually identify this issue in a blind test.  Measurements are one thing, what you hear is another.

[sts9fan]

Picoseconds people 10x10^-12 seconds.  Now if you told me nanoseconds I would be all ears but PICO!!  thats just silly....


No, just your response.

I don't understand how any of you people can make claims about jitter not being this, that, or the other thing, without stating magnitude, frequency spectrum, or level of data-correlation.

The bottom line is that depending on all of those 3 criteria, jitter can be problem in any system. Its causes are many. Anything from SPDIF, which is a joke, to CD players that stick the clock circuit in the digital filter chip. Just because some people of dubious reputation make products to address this issue is no reason to dismiss it as another "solution" looking for a problem to fix.

Pat

I made no claims.  So is there a duration limit at which regardless of magnitude or frequency spectrum is inaudible?  Or do you claim that an large blip at 10*10^-100 seconds will be heard?  What is this limit? 
You can always tell the people with that have financial interests from the hobby folk.

[Ethan Winer]

Wow, I make one innocent comment and we're up to five pages in less than a day.

is Robert Harely from TAS delusional with his sonic portrayal of jitter in a system?

Yes, fer sher. As are all the other people who claim to be able to hear jitter (and dither). At 120 dB or more below the music, jitter is a total non-issue regardless of the jitter spectrum or randomness. I doubt jitter was ever a problem because even cheap crystal oscillators like you find on a $25 SoundBlaster sound card are very stable in this context. But even if jitter was audible when digital audio was first introduced, it surely hasn't been a problem for at least the past 20+ years.

When I Googled "jitter demonstration" as suggested, Arny Kruger's PCABX site came up first, as it should. Note that Arny's graphs show damage to the audio only when the jitter is made artificially high. At typical levels it's impossible for jitter to be audible simply because its so soft. Again, it's way below the noise of the digital medium, not to mention the masking effect which can hide artifacts even when they're only 10 or 20 dB below the music.

The notion that jitter can cloud imaging and obscure presence etc is pure fiction. Jitter manifests as artifacts that are added to the sound. Which brings us to acoustics. Imaging is directly affected by room reflections. The more early reflections you have, the more clouded the sound becomes. Especially when the reflections are loud. In a typical size room without treatment at the first reflection points, the combined reflections from the sides, floor, ceiling, and wall behind you can easily be as loud as the direct sound from the speaker! Even with treatment reflections are often only 20 dB down. This is literally 100,000 times (100 dB) more damaging than artifacts that are 120 dB down. Yet achieving even -20 dB for early reflections is enough to make a huge improvement in clarity and imaging.

I've posted this link before and I'll post it again now:

Why We Believe

I'm convinced that comb filtering is the root cause of people believing they hear a change in the sound even when no change is possible. That, and of course delusion.

Peace.

--Ethan

[ctviggen]

Picoseconds people 10x10^-12 seconds.  Now if you told me nanoseconds I would be all ears but PICO!!  thats just silly....


No, just your response.

I don't understand how any of you people can make claims about jitter not being this, that, or the other thing, without stating magnitude, frequency spectrum, or level of data-correlation.

The bottom line is that depending on all of those 3 criteria, jitter can be problem in any system. Its causes are many. Anything from SPDIF, which is a joke, to CD players that stick the clock circuit in the digital filter chip. Just because some people of dubious reputation make products to address this issue is no reason to dismiss it as another "solution" looking for a problem to fix.

Pat

I made no claims.  So is there a duration limit at which regardless of magnitude or frequency spectrum is inaudible?  Or do you claim that an large blip at 10*10^-100 seconds will be heard?  What is this limit? 
You can always tell the people with that have financial interests from the hobby folk.

Ah, picoseconds is 10^-12, not 10^-100.  Secondly, jitter is an error around where something should happen.  There really is no "blip"; instead, it's a "constant" error.  Can one hear jitter in the picosecond range?  That, I don't know.  However, it's better to at least know what jitter is and is not in order to argue effectively one way or the other.  Here's a Wikipedia article about jitter:

http://en.wikipedia.org/wiki/Jitter

[martyo]

Thanks again for your wisdom Ethan. 

[miklorsmith]

I didn't think jitter was a noise issue quantifiable as dB below signal, rather a timing error OF the signal.  I might be wrong as my real understanding is roughly equal to a kangaroo's.  However, if this is true it is pervasive.  I will say my Lessloss rig is freakin' outstanding, with a cheap Rega transport.  They're way into jitter smashing.

It might be easier to describe the sound of jitter in terms of its absense but even that's difficult because you have to be able to listen through so many other elements between components

[Daygloworange]

Ethan,

Are you sure it's only below the noise floor? The way I see jitter explained is that it distorts the proper reproduction of the waveform in the encode/decode transfer function of and A/D or D/A converter.

Cheers

[Bob in St. Louis]

Are you sure it's only below the noise floor? The way I see jitter explained is that it distorts the proper reproduction .........

This was my understanding as well.

Bob

[DevillEars]

Maybe the question should be examined from the opposite perspective:

"What are the audibly discernible differences when levels of 'jitter' are reduced, and are they, in fact, improvements or just differences?"

I can only comment from one personal experience - and that was back in 1995, when my trusty old Rotel RCD965BX was "upgraded" by the installation of a Trichord Research "Clock-2" module.

The Clock-2 comprised a daughterboard plus a 5ppm accuracy crystal oscillator (clock) and was installed on site in an hour one Saturday afternoon.

The difference between "before and after" were noted by the installer (a friend), my daughter and myself.

The major areas of difference:

• Improved retrieval of low-level detail
• Improved soundstage width and depth (linked to detail?)
• Improved image stability within the soundstage
• Improved bass reproduction - tauter, less 'wooly'
• Improved treble - cleaner with less 'brightness'

These differences were clearly discernible but not earth-shattering. They were also all clear 'improvements' to the sound quality and not just 'differences' - this was a consensus view of the three of us involved.

So to come back to the question posed in the original post:

"Re: The sonic signature of jitter and how to conquer it????"

By taking the observed 'before and after' observations above and 'turning them around', I guess one could summarise the 'sonic signature of unnecessarily-high levels of jitter' as including:

• Lackof low-level detail retrieval
• Narrow and shallow soundstage
• Images that move within the soundstage
• Poorly defined and loose bass reproduction
• Bright and grainy treble reproduction (probably the most obvious)

As far as 'conquering jitter' is concerned, two approaches: one, prevention; two, cure!

Prevention involves addressing jitter as close to the optical read part of the process (in the transport section) as possible (using high-accuracy clocks, etc)
Cure entails re-clocking just before feeding in the DAC chipset

There are a number of products on the market that either incorporate these technologies or can be either retrofitted (a la Trichord's Clock-2) or inserted between CDT and DAC (eg Genesis' 'Digital Lens', Theta's 'Jitter Jail', etc.)

[woodsyi]

Ethan,

I have your traps among others.  I heard a difference in my situation (using a reclocker) of the same order of magnitude as having early reflection point treatment vs. not.  If I am delusional, I could be delusional about the effectiveness of the traps too.   

[sts9fan]

Ah, picoseconds is 10^-12, not 10^-100.  Secondly, jitter is an error around where something should happen.  There really is no "blip"; instead, it's a "constant" error.  Can one hear jitter in the picosecond range?  That, I don't know.  However, it's better to at least know what jitter is and is not in order to argue effectively one way or the other.  Here's a Wikipedia article about jitter:

Right I understand but there must be a limit.  I only said 10^-100 as a point.  What do people working on this issue believe that limit to be?  If they don't know how can they effectively work on the problem?  From my perspective and occupation (analytical chem)  if you do not have a firm understanding of the scope and limits of the problem it is difficult to solve.  I am still trying to understand this issue so I am not making any accusations.

[Rx8man]

I'm with all the others who mentioned the "timing issue" in the squarewave form reproduction.

This is making the A/D and D/A converters work overtime in producing a crappy sound (whether you hear it or not)

My take is, the only way to avoid this whole dilemma is, take music off a hard or flash drive and pass it to a DAC, but I'm not spending a house mortgage to do it.

[Daygloworange]

Are you sure it's only below the noise floor? The way I see jitter explained is that it distorts the proper reproduction .........

This was my understanding as well.
Bob

This is how Stereophile explains what jitter is actually doing. I'm not claiming it is the true definition, but it seems logical.

http://www.stereophile.com/reference/1093jitter/

Cheers

[grsimmon]

www.benchmarkmedia.com/appnotes-d/

[grsimmon]

And for laughs, in case you haven't seen this:

http://redwing.hutman.net/%7Emreed/

[art]

This is how Stereophile explains what jitter is actually doing. I'm not claiming it is the true definition, but it seems logical.

Cheers

Did anyone read this closely enough to see the section on impedance matching? No......probably not. Gee, I wonder who else says pretty much the same thing.

But, once again, I must point out that talking about jitter and what is and is not audible is meaningless without specifying amplitude, frequency spectrum, and level of data-corrleation. Random-occurring noise is much less noticeable than jitter that is data-correlated.

Pat

[george_k]

I skimmed through this thread and thought I'd chime in with something I've come across.

I recently bought a CD release by the AES called "Perceptual Audio Coders: What to Listen For".

I received it yesterday and quickly browsed through the 2 first sections, one was on the effects of aliasing on music and the other was on sampling.

It's interesting stuff

Here's a quick description:
Low-bit rate audio coding has become a widely used technology during past years. By of the use of sophisticated signal processing techniques, exploiting psychoacoustic phenomena, nontransparent coding results in artifacts sounding very different from traditional distortions which are frequently not obvious at all to the untrained listener. The AES Technical Committee on Audio Coding therefore has started an activity to produce a CD-ROM which presents some of the most common coding artifacts in more detail. The CD-ROM not only explains and comments each of the coding artifacts separately but for each artifact, audio examples are presented, using different degrees of distortion, varying from "subtle" up to "obvious".

http://www.aes.org/publications/AudioCoding.cfm

[AphileEarlyAdopter]

Wow, I make one innocent comment and we're up to five pages in less than a day.

is Robert Harely from TAS delusional with his sonic portrayal of jitter in a system?

Yes, fer sher. As are all the other people who claim to be able to hear jitter (and dither). ..

Peace.

--Ethan

Well..you've got the attention, especially you being an acoustics expert.
But I beg to differ with you. A whole branch of industry (building transports, reviewers and DIYers) cannot be a bunch of charlatans or deluded.
Either you are probably listening at high volumes looking for presence/absense of reflections all the time or you are just not got your listening tuned to the 'high precision' sound of a very low jitter playback.
This is what separates digital playback from analog.  (BTW, what is your system/room like ?)
(Apologies, if I sound rude,(I dont mean to be)  but there is no other way, I can put it. I have ignored countless posts on jitter, but because you are an expert, I have to put my foot down).

[BrianM]

A whole branch of industry (building transports, reviewers and DIYers) cannot be a bunch of charlatans or deluded.

I don't think anyone doubts the existence of jitter as a measurable phenomenon.  The disagreement is over how important, relevant, audible it is.  Building transports and DACs that attempt to address jitter doesn't have to be charlatanism, but it might be gilding a lily.  Lots of businesses promote "advancements" before there's universal agreement as to their benefits.  So no, they're probably not all out to put one over on us, but in a competitive industry everyone is trying to differentiate their products.  Making claims (even measurable claims) about jitter is one way to do so.  The problem is that the difference between good and great in this industry can only ever be a matter of perception, and very subtle perception at that.  People always seem to underappreciate how complex the notion of reliably evaluating the impact/benefit of a component, or a component of a component, necessarily is.  The component that "fixes jitter" may be doing a host of other things well or poorly, and may have been heard -- will have been heard -- under conditions nearly impossible to duplicate by you.  And of course heard by ears other than yours...

All that said, I'm more inclined to listen to those who, rather than swapping components to fix the "problem", swapped out the crystal chip or whatnot, since that's obviously a localized change that leaves everything else in place.

[Daygloworange]

This is how Stereophile explains what jitter is actually doing. I'm not claiming it is the true definition, but it seems logical.

Cheers

Did anyone read this closely enough to see the section on impedance matching? No......probably not. Gee, I wonder who else says pretty much the same thing.

But, once again, I must point out that talking about jitter and what is and is not audible is meaningless without specifying amplitude, frequency spectrum, and level of data-corrleation. Random-occurring noise is much less noticeable than jitter that is data-correlated.

Pat

Pat, I read the Stereophile article, but at a certain point ADD kicks in.   In your opinion, is the explanation inaccurate or wrong?

Can you elaborate in more layman's terms what you see as the important issues pertaining to jitter?

Is it distortion of the waveform? Is it an aliasing? Noise that's being added? Is it across the entire FR spectrum? Where above the noisefloor is it, or is it throughout the dynamic range?

I'd like to learn more about how jitter manifests itself in audio recording and playback.

Cheers