[AphileEarlyAdopter]

...
If there's a general agreement I'll put this together in the next few days, and post CD-quality wave files on my site with links here. . ...

So  far so good...

...
Then, if nobody can tell where the nasty noise comes and goes at -80 or -90, we'll have proven that things like jitter and capacitor distortion at -120 must be inaudible.

So what do you all say - sound like a plan?

--Ethan

NO ..NO ..NO ..No way.  With jitter the sidebands are getting created because the original waveform is not getting recreated (from the digital information) accurately in proper time, because of jitter. So with jitter the sidebands are correlated to the main music signal or tone. Quite likely human beings are able to hear the difference between the good tone and the distorted tone.
If the noise was additive and not correlated with the main signal or tone, people probably may not hear any qualitative difference between the clean tone vs the clean tone + additive noise.

Anyways, give us an example of devices with jitter which create sidebands that are not discernible.
I have tried a Pioneer dvd player, Philips 963sa, Squeezebox and a Oppo 970 in stock form. All these improved in sound (as transports) after some modification/tweaks/different digital cables (which could have changed only the jitter characteristics).

(BTW, jitter does not exist when you are dealing with the digital information, it is when you DAC it using the retrieved clock signal coming over the SPDIF jitter happens. Basically the retrieved clock frequency keeps changing, this is what jitter is).

[darrenyeats]

Can someone specify a test which WILL test jitter? What if we used the  Pioneer dvd player, Philips 963sa, Squeezebox and a Oppo 970 and then applied AphileEarlyAdopter's tweaks and did blind listening tests? Would that nail it?

The problem with this is that trying to nail it down in pure technical terms is very difficult. You could draw a link between that and it being a popular topic on audiophile forums.

But all we really care about is audibility. Yes jitter is bad, yes there are different forms...but yes there must also be a threshold for each form where it is not audible! The only way we can find out is by some form of listening test!

I suggest the jitter-believers should propose the test, otherwise we'll be back and forth forever.
Darren

PS: This is why I said at the beginning, I just avoid S/PDIF.

[miklorsmith]

Stereophile's Test Disc #2 supposedly has a jitter demonstration track:

http://www.stereophile.com/features/338/index11.html

I have this disc, I'll check it out.  I'm not a tester though, you'll have to look somewhere else for that.

[jhm731]

I think there's more to it than noise levels.  There, I said it.  I can't defend it or quantify it or analyze it or anything else.  If the test subject is noise artifacts Ethan's test is fine but I disagree that's where it ends.

Go ahead, try to argue with that!   

There's no need to argue, Pat has already made this point perfectly clear:

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

[AphileEarlyAdopter]

I suggest the jitter-believers should propose the test, otherwise we'll be back and forth forever.
Darren

Very simple. Find a player (not the ones that cost $10000 ) with electrical and toslink digital outputs.
Connect a cheap coax cable to the electrical output
Connect a Glass toslink to the toslink output.
Connect both to a DAC that does not have any jitter reduction builtin (for eg. Lavry DA10 disqualifies)
Now switch between the two outputs.
Ofcourse, some people may not notice any difference between the two.
I can tell the difference with a stock Squeezebox (I can take the test in SF Bay Area).

(BTW, I stumbled upon jitter accidentally. I was initially running a MSB Link DAC with a cheap toslink, thinking digital is digital and how can a cable make a difference. Somebody gave a Acoustic Zen digital cable and voila the difference was too stark. Later I read about SPDIF and jitter).

..
PS: This is why I said at the beginning, I just avoid S/PDIF.

You are probably right in one way, but single box players are difficult to execute (from an electrical design point of view). It probably is simpler/easier with say, the Squeezebox and probably explains the popularity of the 'analog mods' done by boldercables.com to it.

Anyways, there is no such thing as 'belief in jitter'. It is  real, it is measured and it can systematically be reduced. Lots of designs/mods exist for it. Just like anything in audiophilia, it is all relative. Things get difficult to hear as you keep improving the quality of your system. As for me, I might spend $2k to eliminate jitter in my system. But I may not spend $20K on a 'perfect' player.

[*Scotty*]

AphileEarlyAdopter,virtually all modern DACs have a built in oscillator that is controlled by an external crystal. This is present to allow the DAC to function and also constitutes a method to control jitter. I don't think a DAC exists that does not have some provision for jitter reduction built into the chip itself. Your proposed test does not eliminate the noise that is contaminating the ground of the player/transport
which your have transmitted on to the DAC via the coax cable connection. The fiber optic connection breaks the ground connection and does not contaminate the downstream component. I doubt that you are testing for jitter alone with this methodology.
Scotty

[Ethan Winer]

Very simple. Find a player (not the ones that cost $10000 ) with electrical and toslink digital outputs.

I'm trying to find a test we can all try at home. Versus a test where people have to get together at one place. I do not accept that such a test cannot be devised. I call that a stall tactic from people who know they will not be able to identify jitter versus no jitter blind. So all they can do is object to any proposal I make. If I propose making a pair of files with different amounts of jitter, they'll say the jitter is swamped by other things in the various systems we all have. If I invite people here they'll say jitter is so subtle that being in an unfamiliar listening room will invalidate the test. Or they'll throw up the usual arguments against testing, such as it breaks the mood and doesn't allow living with a component for an extended time to learn to hear subtle changes.

I guess jitter is hugely important and totally obvious except when you have to pick it out blind.

So it's a lose-lose for the folks here who truly do want to learn if usual amounts of jitter are audible because those that believe in jitter - or say they believe in jitter - are afraid to put this to the test. There, I said it. Prove me wrong.

Folks, if you believe there's more to "it" than noise or a noise equivalent, then please tell me what I can put into pair of Wave files for all here to audition in the comfort of their own listening room on a system they're used to. If your answer is "It can't be tested," then I call foul and say you've by default admitted to all of my above points.

Let's say that jitter is more than just artifacts, and it really does smear time or whatever you want to call it. Why do you believe that infinitesimal amounts of time smear are audible? Please show us properly conducted research that shows at what amounts jitter can be reliably identified. I have asked for that before in this thread, and it was conveniently ducked. Most audio professionals have heard scrape flutter on an analog tape recorder. We've also heard analog tape that sounds gorgeous, even though all analog tape has some amount of flutter. So this means that flutter, which is easily measured, can be correlated to how much is audible. By extension the same can be done with jitter. I bet this has already been done! So let's hear it believers - at what level is jitter detectable? Not what you think based on sighted experimenting, and certainly not anecdotal evidence. Rather, show us hard science based on real research. More important, let's hear your proposal for a test I can assemble for all here to try.

Thanks.

--Ethan

[miklorsmith]

Ah, the beauty of being a non-tester - I don't care to prove it and I don't care how hard you try to prove it.  Provers tell me SET amps can't sound good so I'm off the train at the first stop.

However, I misunderstood your original offer Ethan.  I thought you were saying you'd add some low-level noise to a downloadable file.  Are you actually offering to create jittered files for audible testing?  That would be interesting and I'd give it a whirl.  I don't promise to do anything blind, 'cuz it ain't fun.

[*Scotty*]

Here is an important point to remember, if you come to Ethans' courtroom you are subject to his rules of evidence.  This has never been a debate about whether jitter is an audible problem in our systems except in as much as Ethan has been humored in the direction the thread has taken. I don't think people working in the field of digital audio are working on controlling the impact of jitter because they have nothing better to do. Of course this is just my opinion.
Scotty

[JeffB]

After some thought, I think jitter can be represented as noise after all.

If one considers two samples points.
point A: level 16384  2^14
point B: level 16448  2^14 + 2^6.

What does a DAC do? 
Create a sample voltage of 16384*offset for 23us(1/44100).
Then create a sample voltage of 16448*offset for 23us(1/44100).
offset= 2 Volts / 65535.

So if point A is applied early and point B on time, then the voltage is applied for longer than it should be.
I can kind of see this as being equivalent to applying a greater voltage for exactly 23us.
So if point A arrives early say at -7us then
16384 * 30/23 = 21370 = the voltage needed to simulate the jitter.

One could take a .wav file and modify the levels by
new_levelA = levelA * (23 + jitterB - jitterA) / 23

23 is really an abbreviation for 1e6/44100.

One could randomly use a jitter value between
0 and x microseconds, or should it be nanoseconds.
Create a .wav for every x between 1 and 7us.

I could do this, but I am very busy.  I might not get around to it for a while.

[AphileEarlyAdopter]

..  This has never been a debate about whether jitter is an audible problem in our systems ..
Scotty

It is a problem in Ethan's system too

[AphileEarlyAdopter]

..
One could randomly use a jitter value between
0 and x microseconds, or should it be nanoseconds.
Create a .wav for every x between 1 and 7us.

I could do this, but I am very busy.  I might not get around to it for a while.

Well..you dont have to do this. Stereophile already measures jitter.
Lets take a 1Khz sine wave, encode it as a wav, burn cd, play it.
When you measure the output at the preamp, it should be an identical sine wave.
It will not be the case, it is a slightly distorted form of the original sinewave.
Now, if you do Fourier analysis of this (ie. decompose this complex wave into sinusoidal components) you get the sidebands that Ethan mentions.
My point is that the sidebands are related to the main signal/tone that distortion caused by jitter (ie. the sidebands) make the main signal/tone blurry or whatever (as people perceive jitter). Ethan continues to insist that a little bit of time smear cannot be heard.
I am now at a loss to explain things more. Jitter is so well-established in the sense, that it is like saying transports do not make a difference to the sound or digital cables do not affect sound quality.
I will post later, on things, I have done to reduce jitter.

[JeffB]

My whole last post is completely in error.
It simply equated work done.
A louder signal over a shorter time period won't sound anything like a softer signal over a longer time.

I was trying to think of a way to mathematically generate a .wav file with jitter.
I now don't see a method to do this.

What is needed then is a method to create audio with low jitter and high jitter, and then record them.
If Stereophile measures jitter then one could record the output from two different players, one with low jitter and one with high jitter.
However, then you are comparing a lot of things other than just jitter.

Ethan, if you can produce a .wav file with jitter, how are you going to do this.

[darrenyeats]

Jitter is so well-established in the sense, that it is like saying transports do not make a difference to the sound or digital cables do not affect sound quality.
I will post later, on things, I have done to reduce jitter.

CD transports make a difference...optical drives used to rip onto computer don't.
Digital cables make a difference using the brain-dead S/PDIF protocol...cables used in computer networks don't make a difference.
I could go on:
Speaker cables might be significant when you pump every octave down a single wire into a passive crossover...they aren't when you have active amplification.

A lot of audiophilia is wrong paradigms flogged to within an inch of their rather pointless lives. It all reinforces my belief it's a sociological phenomenon.
Darren

[miklorsmith]

I think it's a collection of phenomena, which is why one's own fleshy SPL meters are so important.

[Ethan Winer]

Ethan continues to insist that a little bit of time smear cannot be heard. I am now at a loss to explain things more.

Yes, a little bit cannot be heard. Even you must agree that at some point jitter will be too soft to notice, yes? So no need to feel at a loss. All you have to do is say at what level you believe jitter is audible, and show hard evidence for why you believe that.

Ethan, if you can produce a .wav file with jitter, how are you going to do this.

Great, question. I imagine a vibrato plug-in could do this, but the trick will be to correlate the amount of vibrato added with a dB level of sideband artifacts. I'd have to add small amounts of vibrato to a sine wave, use FFT analysis to relate how much vibrato gives how much sidebands, and then apply the same amount of vibrato to music. I can do this easily with sine waves using the standard tools in Sound Forge. I'm not sure how to do that accurately with music files.

This is why I proposed adding nasty sounding noise to sine waves and music. In the larger picture that is exactly the same as adding controlled amounts of jitter - either way it's adding harmonically unrelated artifacts. And so far nobody has explained why such a test is not just as telling as actually applying jitter. Adding noise can also prove that capacitor distortion 120 dB below the music is inaudible. So if I can prove to everyone's satisfaction that very soft artifacts are inaudible, by extension that disprove the theory that very soft jitter is audible too.

For at least the fourth time now, if the nay-sayers won't accept my test, let's hear your better test proposal so we can settle this for once and for all. Doesn't everyone here want to know at what level artifacts are no longer audible and damaging? Don't even the nay-sayers want to know this?

--Ethan

[miklorsmith]

I say jitter is more than noise, ergo adding noise to an otherwise "clean" file won't answer the question.  Others in this thread have echoed these thoughts.

[AphileEarlyAdopter]

Jitter is so well-established in the sense, that it is like saying transports do not make a difference to the sound or digital cables do not affect sound quality.
I will post later, on things, I have done to reduce jitter.

CD transports make a difference...optical drives used to rip onto computer don't.
Digital cables make a difference using the brain-dead S/PDIF protocol...cables used in computer networks don't make a difference.
I..
Darren

ok, that means you can hear the effects of jitter. You are an audiophile with golden ears

[AphileEarlyAdopter]

Ethan continues to insist that a little bit of time smear cannot be heard. I am now at a loss to explain things more.

Yes, a little bit cannot be heard. Even you must agree that at some point jitter will be too soft to notice, yes? ..
--Ethan

Ethan, I notice a change or softening of your stance. Now you need to talk about jitter in the actual terms it is measured i.e peak-to-peak variation in time/picoseconds  (just ignoring the spectrum for simplicity sake). If you use this parameter, most CD/DVD players under $1K have very high jitter. Also, most electrial digital cables suffer from reflections because of non-standard (not 75ohm) termination in consumer equipments. Cheap toslinks make a bad connection too (adding interface jitter).
If you do not recognise these, you are doing a disservice or misleading audiophiles here.

[AphileEarlyAdopter]

Steps to reduce jitter -

• Reduce vibrations to your component. Use a rack with spikes and place each shelf on spikes. Lots of shelves, vibration reducing components available.
• Use a power conditioner or make sure power is clean of spikes/noise etc. Balanced power conditioner makes quite a bit of difference
• A component with good power supply makes the best of the oscillator/clock in the device. 50% of the cost of the pricey Halcro amp goes into designing a power factor corrected power supply for it. After market power cords help improve dynamic demand of current of the device. These dont have to be pricey. Simple DIY designs make quite a bit of difference
• In the case of CD/DVD players, a clean CD with some anti-glare spray helps the laser track efficiently reducing too much servo tracking and in turn putting more demands on the power supply, which will affect the whole system and jitter.
• With computer based play back, it is much easier to isolate the audio output device than to use the builtin soundcard. Examples would be USB/Firewire/Network(like Squeezebox) sound cards/devices. It will be easier to get a power supply to these devices than to the whole computer.

Here is my system -

Cryoed Hubbell wall outlet -> Empirical Audio power cord -> Furman Power Factor Pro -> Black Sand Violet power cord -> Blue Circel MR1200 Balanced Power conditioner -> Modded SB3 with modded Elpac power supply -> Zu Ash -> Behringer SRC2496 (with Vh Audio power cord)  -> Sound Professionals Glass Toslink -> Panasonic XR55 --- (bi amp) ---> Silverline Sonatina speakers.
My system is all digital till the speakers. Any change in the above setup I immediately notice a difference. So I am used to hearing the effects of jitter.