Yes you CAN hear jitter! - Page 4 - AVS Forum
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post #91 of 134 Old 06-23-2012, 10:02 AM
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Originally Posted by amirm View Post

You asked what jitter sounded like and according to you, they all gave different answers. That is the only valid answer: i.e. jitter can sound like anything it wants.

Interesting. So Amir in your world jitter is a living, sentient creature that morphs at will? Wow!

In my world jitter is a certain kind of frequency or phase modulation distortion that is characterized by its amplitude and spectral content as well as that of the signal that it modulates.

That means that it has characteristic sound depending on the relevant parameters.

Think about it - if jitter could sound like anything, how could an audiophile know for sure that he had jitter and perhaps not some other kind of distortion?
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OK, tell us what it sounds like.

Amir, since you are such an avid scholar of Zwicker and Fastl, why don't you tell us what they say about how jitter sounds?
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post #92 of 134 Old 06-23-2012, 10:11 AM
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Originally Posted by Swampfox View Post

5) Jitter below 1 nanosecond is clearly inaudible, and audibility is probably in in 20 - 30 ns range for trained observers.

Agreed. Just to put this in proper perspective, the graph below showing jitter noise is from The Art of Digital Audio by John Watkinson. It shows the amount of noise you can expect at various frequencies, with the noise floor of various bit depths as a reference.

--Ethan

jitter_noise.gif

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post #93 of 134 Old 06-23-2012, 10:13 AM
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Originally Posted by dlarsen View Post

The Pope can be hit by a meteor. This simulation shows it:

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LOL, that's perfect! biggrin.gifbiggrin.gifbiggrin.gif

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post #94 of 134 Old 06-23-2012, 10:31 AM
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Quote:
Originally Posted by arnyk View Post

Interesting. So Amir in your world jitter is a living, sentient creature that morphs at will? Wow!
Yes.
Quote:
In my world jitter is a certain kind of frequency or phase modulation distortion that is characterized by its amplitude and spectral content as well as that of the signal that it modulates.
That doesn't describe the sound. If I asked someone what an sounds like when an amp clips, do you think the answer is, "the waveform starts to look like a square wave?"
Quote:
That means that it has characteristic sound depending on the relevant parameters.
Oh, if it depends on relevant parameters, how can it have one sound?
Quote:
Think about it - if jitter could sound like anything, how could an audiophile know for sure that he had jitter and perhaps not some other kind of distortion?
He wouldn't and he could be confused. The question is, why did you make the mistake of thinking you know the answer? I read your post as one of superiority. You knew the answer but audiophiles didn't. Therefore, we should listen to you, not them. After just a couple of questions, you concede that changing the parameters changes the nature of distortion. If the nature of distortion changes, then what it sounds like changes. Ergo, two people can tell give you two different answers and both be right. And you wrong for expecting one answer.
Quote:
Amir, since you are such an avid scholar of Zwicker and Fastl, why don't you tell us what they say about how jitter sounds?
Again you ask me to answer your question? You said you knew what jitter sounded like. You said you knew that from extensive experience in how to create it. Another post has gone by and we still don't know what Jitter *sounds like*. If you know what jitter sounds like why not tell us? Or do you not know and we should ask the experts you mentioned?

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post #95 of 134 Old 06-23-2012, 12:47 PM
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Originally Posted by amirm View Post

Again you ask me to answer your question?

My question?

Why would anybody be interested in my answer to a question I asked?
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You said you knew what jitter sounded like. You said you knew that from extensive experience in how to create it.

Right, and then I asked you to tell us what I sounds like. Obviously, I will compare what you say to what I know to be true. I will cite Zwicker and Fastl so that people can see that I'm not making up the answer.
Quote:
Another post has gone by and we still don't know what Jitter *sounds like*.

That's wonderful Amir. Thank you for admitting that you don't know what Jitter sounds like. It makes something rather unflattering and bizarre out of all of your claims to have heard it.
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post #96 of 134 Old 06-23-2012, 12:49 PM
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Quote:
Originally Posted by Ethan Winer View Post

Agreed. Just to put this in proper perspective, the graph below showing jitter noise is from The Art of Digital Audio by John Watkinson. It shows the amount of noise you can expect at various frequencies, with the noise floor of various bit depths as a reference.
--Ethan
jitter_noise.gif

If you include the well-known fact that the actual noise floor on even the best recordings is maybe 12-13 bits down, the probability of someone actually hearing jitter is very slight indeed.
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post #97 of 134 Old 06-23-2012, 01:46 PM
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Originally Posted by arnyk View Post

My question?
Why would anybody be interested in my answer to a question I asked?
What??? Here was the conversation again:
1. You say audiophiles don't know what jitter sounds like.
2. You say you know what it sounds like because you have created it.
3. I ask you to tell us what it sounds like.
4. You ask *me* what it sounds like instead of answering.

Now you say it was your question? Can you tell us what the darn thing sounds like or not?
Quote:
That's wonderful Amir. Thank you for admitting that you don't know what Jitter sounds like. It makes something rather unflattering and bizarre out of all of your claims to have heard it.
So if you do.... tell us. What does jitter sound like? What does jittter sound like? What does jitter sound like? Hope you don't miss that I am still waiting to see you give the same answer you expected from audiophiles: what does jitter sound like. smile.gif

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post #98 of 134 Old 06-23-2012, 02:03 PM
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Quote:
Originally Posted by amirm View Post

. . . What does jitter sound like? What does jittter sound like? What does jitter sound like?
High frequency noise, about a 100db down, just as the graph that Ethan posted would predict.

Ok, I admit, I have not heard it, but I have seen it on a scope. It looked like white noise, but starts in the kHz range and curves up as the frequency rises. I had to get a lot of other noise-sources out of the system before it was at all visible.
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post #99 of 134 Old 06-23-2012, 02:06 PM
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Quote:
Originally Posted by amirm View Post

What??? Here was the conversation again:
1. You say audiophiles don't know what jitter sounds like.
2. You say you know what it sounds like because you have created it.
3. I ask you to tell us what it sounds like.
4. You ask *me* what it sounds like instead of answering.

As I recall, step 4 came before step 3.

The way you seem to work Amir, if I tell you what jitter sounds like then there is a good chance that you will say that is what you knew all along.
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post #100 of 134 Old 06-23-2012, 04:17 PM
 
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Quote:
Originally Posted by amirm View Post

What??? Here was the conversation again:
1. You say audiophiles don't know what jitter sounds like.
2. You say you know what it sounds like because you have created it.
3. I ask you to tell us what it sounds like.
4. You ask *me* what it sounds like instead of answering.
Now you say it was your question? Can you tell us what the darn thing sounds like or not?
So if you do.... tell us. What does jitter sound like? What does jittter sound like? What does jitter sound like? Hope you don't miss that I am still waiting to see you give the same answer you expected from audiophiles: what does jitter sound like. smile.gif
amirm, you keep posting as if this never took place: http://www.avsforum.com/t/1326576/usb-vs-hdmi-for-2ch-audio-to-receiver/30 rolleyes.gif
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Originally Posted by amirm's store website 
Invariably, by the time I get to this point of the argument with someone, the conversation turns into “yes but… is it audible?” As unfair as it might be, I am going to punt that question.
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Originally Posted by amirm View Post

This is an example of periodic 3Khz jitter, modulating a single 10 KHz tone:





You see that those additional spurs created on either side that was not in the source? Well, depending on where they land, they can have the effect of distorting what was there. They also step on low level detail that is of lower magnitude than them.


to the extent that some of what you consider soundstage comes from reverbs in the original recording and the spurs above step on them, you will also lose a sense of space although I would not call it soundstage widening per-se.


If jitter is random, then it works to simply raise the noise floor. Here is an example of it, albeit in a situation where it is still not audible:





This form is benign since it is not modulating the original signal in any way.


Net, net, as I mentioned other than the one guy, the rest deserve to walk on the red carpet
.

Not necessarily. If you are able to turn off those circuits and hearing their effect, then you approximate the situation with the DAC where you don't have any video circuits to worry about.
Quote:
Originally Posted by amirm View Post

But how do you know the sound of jitter? Now, you could tell me ignorance is bliss. But I am not convinced. Trained listeners are not superhuman. But rather they are more reliable in blind testing because they have a calibrated reference and know quickly how to find an artifacts.


I can't easily teach you how to hear jitter (I wrote a bit earlier).
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post #101 of 134 Old 06-23-2012, 04:36 PM
 
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Lets not forget, amirm has been caught lying many times on this forum.
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Originally Posted by amirm View Post

I didn't tell you it takes more money to create a more audible improvement. I said "audio performance."
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Originally Posted by amirm View Post

It means that to get equal audio performance in an AVR, you may have to spend a lot more money than a dedicated audio DAC. And even then, you may not quite get there.


Here is a way to experiment with this idea. Does your AVR have a button to turn off the video circuits and front panel display? If so, hook up a CD/DVD player using S/PDIF coax cable. Play something quiet with lots of ambiance. Now turn up the volume good and loud (or else use headphones). Play it with the video and front panel circuits on (on both the source and AVR) and then turn them all off. Do you hear a difference? If you do, then the above factor is in play.
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Originally Posted by arnyk View Post


No, the question was:


"Just curious if there are any differences in SQ between using the USB out on my Macbook and PC, VS using the HDMI out?"


Your answer was:


"Depending on the USB implementation, yes."


The question was not about measured performance, it was about sound quality. However, if we consider only the question for which actual reliable evidence has been presented, the proper answer would be:


"The answer depends on the implementation of the conversion from USB to analog audio signal, and the implementation of the conversion from HDMI to analog audio signal."


Your surreptitious changing of the question that the OP asked is yet another distraction.
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post #102 of 134 Old 06-23-2012, 06:13 PM
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Originally Posted by arnyk View Post

As I recall, step 4 came before step 3. The way you seem to work Amir, if I tell you what jitter sounds like then there is a good chance that you will say that is what you knew all along.
Hmmm. So you are afraid of answering due to my reaction? Let's try it this way. This is what you said originally:
Quote:
Originally Posted by arnyk View Post

Once upon a time I asked a bunch of audiophiles what jitter sounded like. I got as many answers as there were audiophiles.
Unlike them I actually know what jitter sounds like. I have the ability to add variable amounts of jitter at different frequencies to musical signals. I have several ways to do this, some I do with signal processing that is applied to a digital signal in a cable, and some that I do by making changes to .wav files. None of the audiophile's answers seemed to indicate to me that they knew what jitter sounded like.
Was this conversation public so that you can link to it so that we can see the audiophile answers? Or do you secretly hang out with audiophiles when we are not looking? smile.gif Either way, what did they say it sounded like?

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post #103 of 134 Old 06-23-2012, 06:26 PM
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Originally Posted by arnyk View Post

If you include the well-known fact that the actual noise floor on even the best recordings is maybe 12-13 bits down, the probability of someone actually hearing jitter is very slight indeed.
How is it well-know? Is there a research paper I can read on that? I assume you still think the ex president of Audio Engineering Society is wrong in the two papers where he outlined the dynamic range could be even higher than 20 bits?

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post #104 of 134 Old 06-24-2012, 04:30 AM
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Quote:
Originally Posted by amirm View Post

Quote:
Originally Posted by arny 
If you include the well-known fact that the actual noise floor on even the best recordings is maybe 12-13 bits down, the probability of someone actually hearing jitter is very slight indeed.
How is it well-known?
Why wouldn't anybody who was interested not know it?
Quote:
Is there a research paper I can read on that?

Amir, please tell me that your computers have been expunged of all search engines and there are no public libraries within driving distance of your home. Otherwise, your demonstrated inability to do effective research would seem to be inexcusable:

http://www.audiology.org/news/interviews/Pages/20081124a.aspx

"Yes, that seems to be what's going on. We actually go from a 50-70 dB dynamic range in live orchestral concerts and a similar dynamic range in some CD classical recordings. And then the range between “quiet” and “loud” in some rock music is 5-10 dB."

http://sound.westhost.com/dynamic-range.htm

"The dynamic range of orchestral music can be as much as 70dB, "

http://www.gearslutz.com/board/985005-post34.html

"Show me a recording with even 80 dB of actual musical dynamic range... One of my most dynamic recordings is that of a solo accordionist playing Cage and Satie, who reached 50 dB... Many amateur or semi-pro orchestras won't be able to compete with that..."
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post #105 of 134 Old 06-24-2012, 07:02 AM
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Originally Posted by arnyk View Post

Why wouldn't anybody who was interested not know it?
Well, people who "know" it like Fielder, the ex-president of AES, have researched it with proper understanding of psychoacoustics and what they have published is the opposite of what you said. You seem to think Googling and finding two other guys like you on the Internet makes something a fact and a counter to major research such as Fielder's. I am sure I can find two people who say if you smoke oregano, it will make your cancer go away if I googled hard enough smile.gif.

As I explained in excruciating detail in not one but two threads with you, you cannot use a single number to represent the noise floor of the system/recording. That is just wrong. It ignores pyschoacoustics of our hearing system that says our ear's sensitivity to noise/tones can vary as much as 70 db depending on its frequency! Since dynamic range is the ratio of the maximum level to the RMS value of noise floor, then by definition the dynamic range is not one number but many. Take your car. Do you think it has a single gas mileage no matter how you drive it? Can you use the city or highway mileage number and think that represents your situation in all driving conditions? Of course not. That example is actually far more generous to your case than it should be in this case. This is example research from Fielder's papers:

i-263sWVN-XL.png

We see that there are indeed noise levels that reach as high as 50 dB in low frequencies and hence, if you have 123 dB as one of your sources says as the peak, then the difference seems to be 73 dB. But the ear is not sensitive in that low frequency region as the graph shows. The noise level of the recording studio for example drops to nearly 0 dB at mid frequencies where our ears are most sensitive. Now subtract 0 dB from 123 and what do you get for your dynamic range? Yup, 123 dB. And what is 123 dB expressed as bits? 123/6 = 20.5 bits. Far cry from your 12-13 number. Again, it is not me that is saying this but a person who has researched this area extensively and is frequently referenced in other research.

So unless you have proper research that includes this kind of psychoacoustics analysis and has been published some place, please excuse us for not accepting it as "well-known" fact. You are trusting a dumb meter reading and getting dumb conclusions as a result.

And oh, what I am telling you will hopefully come out in the next issue of Widescreen Review magazine. I get so tired of arguing some points over and over again so I decided to turn these highly debated poins into easier to read articles. I will put the one addressing this one online once it comes out in print. Then it will show up to counter these wives' tails the next time someone Googles for this information smile.gif.

Edit: can't seem to write this morning smile.gif. Fixed spellings.

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post #106 of 134 Old 06-24-2012, 07:39 AM
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Originally Posted by amirm View Post

I get so tired of arguing some points over and over again so I decided to turn these highly debated poins into easier to read articles.



Edit: can't seem to write this morning smile.gif. Fixed spellings.

some smile.gif
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post #107 of 134 Old 06-24-2012, 08:50 AM
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Originally Posted by OtherSongs View Post

Yes you CAN hear jitter!

3. Using an external Benchmark DAC1/HDR via a single 7' digital coax cable for the signal in S/PDIF format.
4. Using same external Benchmark DAC1/HDR via a single 2' digital coax cable for the signal in S/PDIF format.

If you can hear this difference using DBT I bow before you. You should let benchmark maker aware. This should not happen
unless something was wrong with one cable. If you could DBT hear the difference this would be remarkable achievement.
Perhaps you are the ONE! That would be so cool!

Everything I say here is my opinion. It is not my employers opinion, it is not my wife's opinion, it is not my neighbors opinion, it is My Opinion.
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post #108 of 134 Old 06-24-2012, 09:29 AM
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Quote:
Originally Posted by arnyk View Post

If you include the well-known fact that the actual noise floor on even the best recordings is maybe 12-13 bits down, the probability of someone actually hearing jitter is very slight indeed.

For sure Arny. I have never in my life heard the noise floor of a CD, not even when playing music as loud as I can possibly stand then listening quietly after the music stops. And that's the noise floor of "only" 16 bits, which is louder than any jitter coming from even the cheapest sound card. That people obsess over this stuff while ignoring more important "elephants in the room" astounds me.

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post #109 of 134 Old 06-24-2012, 11:23 AM
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Quote:
Jitter-Immune UltraLock™ Clock System
Benchmark’s proprietary UltraLock™ clock system achieves an unprecedented immunity
to jitter. Many modern (and expensive) converters suffer from signifi cant jitter-induced
distortion, generating non-musical sideband tones and digital distortion. Benchmark’s
highly-regarded UltraLock™ clock system ensures that jitter is never a problem, even
under extreme conditions.
Even in the presence of extremely high input jitter, no jitter-induced artifacts can be
detected on the outputs of the DAC1 HDR (using state-of-the-art testing equipment
by Audio Precision). UltraLock™ will block more then 12.5 UI of jitter (@ 1 kHz). The
UltraLock™ clock system easily outperforms even the best-designed two-stage PLL
designs.
The bottom line is this: Benchmark converters will consistently and faithfully deliver
truthful audio without jitter-induced artifacts, no matter what variables are present.

This is from the WEB site for his DAC.


Here's the manual.

It based on an AD1896.

On page 35 - 39 of the manual they present jitter rejection graphs.
The thing is this DAC is really good at rejecting jitter. Overall, it has under -106db of noise when give an signal with 2 micoseconds of jitter. In essence 10 db better than the theoretical noise floor of 16 bit.
They even have a graph showing the unit with 1000 ft of cable.
I was impressed, it's a really nice DAC.
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post #110 of 134 Old 06-24-2012, 11:47 AM - Thread Starter
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Quote:
Originally Posted by OtherSongs View Post

Yes you CAN hear jitter!

3. Using an external Benchmark DAC1/HDR via a single 7' digital coax cable for the signal in S/PDIF format.
4. Using same external Benchmark DAC1/HDR via a single 2' digital coax cable for the signal in S/PDIF format.
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Originally Posted by dknightd View Post

If you can hear this difference using DBT I bow before you. You should let benchmark maker aware. This should not happen
unless something was wrong with one cable. If you could DBT hear the difference this would be remarkable achievement.
Perhaps you are the ONE! That would be so cool!

Smiling.

Perhaps mostly at myself.

Kicked back and just listened to some of the great stereo rips that I've got on my external 2.5" USB HDD.

Then got back to it yesterday, and got down to an 17" RG-6 interconnect, and it sounded as good as the 7' interconnect.

Thought oh-oh; then remembered an earlier comment (see post#12 in this thread) which mentioned Benchmark's advertising: "All digital inputs on the DAC1 HDR (including the USB) feature Benchmark's jitter-immune UltraLock™ clock system"

So switched away from the Benchmark to the Bel Canto DAC3, and still couldn't hear the difference with the short cable.

Got busy this morning and read through the Benchmark .pdf manual (nice manual), and went out to belcantodesign in order to get a non-corrupt copy of their DAC3 .pdf manual (my copy from an past dial-up download was corrupt).

With regard to Ethan and his most recent post, where he mentions "elephants in the room" I'm wryly smiling.

As I'd been meaning to try this for some time, to find out if I could hear a worsening of the sound with shorter coax interconnects, I'll likely continue on for awhile. But won't post about it unless there's something substantive to say.

So I have some mud on my face, maybe a lot of mud.

Since I started the thread, I may respond to those that offer a reasonable comment or question.

The best is the enemy of the good. Voltaire (1694-1778)

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post #111 of 134 Old 06-24-2012, 12:46 PM
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Hm-m-m.... nothling like a poke with a stick in a hornets nest and then enjoy a nice slice of humble pie.

EDIT:
My reasonable comment would be that your original 2' cable is faulty. wink.gif
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post #112 of 134 Old 06-24-2012, 02:17 PM
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Quote:
Originally Posted by Swampfox View Post

Quote:
Jitter-Immune UltraLock™ Clock System
Benchmark’s proprietary UltraLock™ clock system achieves an unprecedented immunity
to jitter. Many modern (and expensive) converters suffer from signifi cant jitter-induced
distortion, generating non-musical sideband tones and digital distortion. Benchmark’s
highly-regarded UltraLock™ clock system ensures that jitter is never a problem, even
under extreme conditions.
Even in the presence of extremely high input jitter, no jitter-induced artifacts can be
detected on the outputs of the DAC1 HDR (using state-of-the-art testing equipment
by Audio Precision). UltraLock™ will block more then 12.5 UI of jitter (@ 1 kHz). The
UltraLock™ clock system easily outperforms even the best-designed two-stage PLL
designs.
The bottom line is this: Benchmark converters will consistently and faithfully deliver
truthful audio without jitter-induced artifacts, no matter what variables are present.
This is from the WEB site for his DAC.
Here's the manual.
It based on an AD1896.
On page 35 - 39 of the manual they present jitter rejection graphs.
The thing is this DAC is really good at rejecting jitter. Overall, it has under -106db of noise when give an signal with 2 micoseconds of jitter. In essence 10 db better than the theoretical noise floor of 16 bit.
They even have a graph showing the unit with 1000 ft of cable.
I was impressed, it's a really nice DAC.
That is a good DAC and has very nice measurements but there is a slight of hand here. This devices uses the above sample rate converter. This does decouple the input jitter from the DAC because they are now truly asynchronous from each other. Jitter measurements as you say, will then be really low.

But there is no free lunch. The sample rate converter now has to track the source rate and switch its ratio. It also needs to interpolate samples to create the slightly higher or lower data rate of the DAC. Tracking errors for the sample rate conversion and interpolation lead to their own distortions which sadly, no one measures. There is a great high level article on challenges of getting DACs to perform well here: http://www.edn.com/design/consumer/4368761/Audio-converter-subsystem-design-challenges-in-the-21st-century

"Finally, I should mention that with a bit of thinking outside the box there is another way to skin this cat. Modern low-cost sample-rate-converter chips (SRCs) are achieving performance which can arguably exceed that of the data converter itself. So you might elect to operate the conversion element at a fixed rate provided by a local crystal (thus eliminating sampling jitter) and to rate convert the converter input or output data. This approach can lead to other issues, and places the responsibility on the SRC to be able to achieve jitter rejection to the same standard as in the PLL model whilst also protecting the quality of your audio crown jewels. "

I highly recommend reading the whole article. It is a bit technical but not too much. It nicely explains why lab performance of DAC chips doesn't translate into system solutions.

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post #113 of 134 Old 06-24-2012, 02:31 PM
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This thread is a treat! smile.gif
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post #115 of 134 Old 06-24-2012, 09:08 PM
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Originally Posted by amirm View Post


But there is no free lunch. The sample rate converter now has to track the source rate and switch its ratio. It also needs to interpolate samples to create the slightly higher or lower data rate of the DAC. Tracking errors for the sample rate conversion and interpolation lead to their own distortions which sadly, no one measures.


They go over that in the theory of operation in the AD datasheet.

"The following worst-case images would appear for fS_IN =
192 kHz:
Image at fS_INTERP – 96 kHz = –125.1 dB
Image at fS_INTERP + 96 kHz = –125.1 dB"
That's lower than a 20 bit noise floor. Since Human beings have a auditory dynamic range of ~120 dB, I'd say it's probably good enough. wink.gif
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post #116 of 134 Old 06-24-2012, 09:10 PM - Thread Starter
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Hm-m-m.... nothling like a poke with a stick in a hornets nest and then enjoy a nice slice of humble pie.
EDIT:
My reasonable comment would be that your original 2' cable is faulty. wink.gif

Smiley indicating a friendly poke with a stick?

It remains a possibility that my 2' cable has some minor and/or tricky fault. Seems questionable at this point, but I never did get back to using it again. I do have it set aside until I get around to checking it out.

FWIW good as the new Panasonic 500 player is, it makes some niggling electronic ticks and pops upon 1st being used for .flac playback from external USB HDD. It may be my specific unit has some minor fault, or maybe it's a 1st production run problem? I don't know how stuff like this plays out with a mass production unit from a big outfit like Panasonic. Just that my easiest fix is to return it now for a full refund, and not get into some drawn out nosebleed with Panasonic's repair unit.

I'll keep my eyes out for comments on the subject; I'll likely buy another Panasonic 500 player in next 3-to-4 months.

The best is the enemy of the good. Voltaire (1694-1778)

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post #117 of 134 Old 06-25-2012, 03:09 AM
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Quote:
Originally Posted by Swampfox View Post

They go over that in the theory of operation in the AD datasheet.
"The following worst-case images would appear for fS_IN =
192 kHz:
Image at fS_INTERP – 96 kHz = –125.1 dB
Image at fS_INTERP + 96 kHz = –125.1 dB"
That's lower than a 20 bit noise floor. Since Human beings have a auditory dynamic range of ~120 dB, I'd say it's probably good enough. wink.gif

You are being way too kind. ;-)

Since all of the participants in this forum have been as blissfully happy as thy get with recordings whose dynamic range is at best about 70 dB, that 120 dB number contains about 50 dB of fantasy.
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post #118 of 134 Old 06-25-2012, 08:31 AM
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Quote:
Originally Posted by Swampfox View Post

They go over that in the theory of operation in the AD datasheet.
"The following worst-case images would appear for fS_IN =
192 kHz:
Image at fS_INTERP – 96 kHz = –125.1 dB
Image at fS_INTERP + 96 kHz = –125.1 dB"
That's lower than a 20 bit noise floor. Since Human beings have a auditory dynamic range of ~120 dB, I'd say it's probably good enough. wink.gif
I have read that and noted it indirectly in the EDN article I quoted. As both I and the author of that article said, that is not enough. The sample rate converter needs to know the ratio of input speed to output speed. To do that, it needs to determine the input speed. Since the input has jitter, it also just like like a PLL, needs to filter and track the input sample rate. When it misses, it is creating distortion but they do not show up as jitter sidebands because the target clock is running steady. It is just that it is at the wrong rate. You will have a strange data dependent non-linear distortion. Worse yet, you can't make it happen with the standard J-Test jitter signal since SRC are immune to that type of excitation due to what I just explained.

Again, I am not saying this device is bad. Indeed, I usually use it as an example of how cheap it is to build good DACs. Just don't want people to get confused by the unusually small jitter numbers in such devices. The jitter per above, is replaced by another type of distortion.

Bottom line, get your source signal as clean as you can. That helps both traditional and SRC based DACs. If a different cable or source helps with that, then you are in a better shape than relying on what the DAC may or may not do.

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post #119 of 134 Old 06-25-2012, 09:06 AM
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OK, looks like Arny, wisely doesn't want to answer what jitter sounds like. The answer as I mentioned was that you can't answer that question.

Earlier someone post my graph with two simple sidebands showing (thanks by the way smile.gif ). That is for an artificial scenario of one and only one sinusoidal jitter. Here it is again:

figure_1_Periodic_Jitter_10khz.jpg

Now let's look at the spectrum of a real device's jitter as measured over its HDMI input by Paul Miller of HiFi News:

i-bh66DFK-XL.png

Doesn't look so pretty now, does it? Instead of just one spike, we now have countless others. Do you think the audible distortion is the same between the two? Of course not. All of those sidebands *combine* their energy and that is what you will hear as distortion, not individual spikes in isolation.

Would another device have the same set of jitter components? Of course not. Why do we have so many? Because there are many sources for jitter and some are square waves and hence, have a ton of harmonics. Think of a microprocessor inside your player waking up once every 1 millisecond to do some housekeeping chore like keeping time. If the CPU is idle and then suddenly starts doing that work, and it is that activity that induces jitter into the clock, the jitter source is squarewave. It is a pulse that goes up rapidly and stays high as long as there is CPU activity. Once that "time out" is done, the CPU goes idle. Looked as a spectrum, it is the squarewave and such a waveform has infinite odd harmonics. So a 1000 Hz (1/1 msec) becomes 1000, 3000, 5,000, etc. Now add to that the front panel display having a refresh, various video devices inside doing their thing, the disc mechanism, etc. They all contribute in some ways to such jitter. Of course, some get filtered and many are attenuated but how much and how well, is equipment dependent.

Take another kind of jitter: random. Here the jitter source is all over the map and doesn't have clean spectrum. Think of a CPU constantly running now. Non-intuitively, this kind of jitter is the least harmful since all it does is create random sidebands and random sidebands is another name for your noise floor.

Then there is the matter of psychoacoustics. That science determines how much of jitter is audible. Arny keeps talking about jitter in analog devices. I have debated that with him and he finally conceded the argument there. In a nutshell, in analog world "jitter" has very low frequency and as such, it heavily gets masked by the music. This is why despite having a lot more of it, it is not objectionable. Arny talks about having tested jitter. Well, because of that misunderstanding, he only simulated low frequency jitter. Here is an example archive from his site: http://home.comcast.net/~arnyk/pcabx/jitter_servo/index.htm. You see him showing *5* Hz jitter. 5 Hz! Why would we want to worry about 5 Hz jitter? That distortion would be in the shadow of the music signal that generates it and as such, inaudible except in huge amounts. Listing to huge amount of 5 Hz jitter does not tell you what "jitter sounds like" in the levels and frequencies that occur in digital systems. Yes, digital systems also have 5, 60 Hz, etc. that that Arny simulated but for the most part, we don't worry about them. It is the higher frequency ones that get past the skirts of auditory masking and make them potentially audible.

So it is all about spectrum. If you don't know that, then you don't know what jitter sounds like. The fixation on the single number jitter value is very poorly placed. We use it to talk about the concept but the reality is that it is the spectrum that determines the level of badness, not that one number.

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post #120 of 134 Old 06-26-2012, 06:05 AM
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OK, looks like Arny, wisely doesn't want to answer what jitter sounds like.

True. As soon as I tell people what Jitter sounds like, then people all over the world are going to start saying that they heard jitter and that is sounds like their paraphrase of whatever I say.
Quote:
The answer as I mentioned was that you can't answer that question.

I can answer the question. And I can answer the question specifically enough to start the ball rollling towards the outcome I fear - all sorts of non-hearers echoing back credible answers based on what I say, only twisted by their own misperceptions and misapprehensions Like I haven't see this happen time after time on AVS - I say something and someone paraphrases what I say in such a twisted way that it now means the opposite of what I said.

The first thing to say is can be said with very few words - if You're looking at a FFT that shows jitter, and any spectral line is more than 100 dB down, the audibility of that sound is easy to predict with 100% certainly. Nobody hears nothing.

People who say that random collections discrete spectral lines that are 100 dB or more down mysteriously clump together and add up to be audible are talking trash. Doesn't happen. Ignores the fact that the human ear uses the louder signals to mask or obliterate the perception of sounds on a massive scale.

Secondly, if a spectral line on a FFT falls below the threshold of audibility on a Fletcher Munson curve, same answer.

Thirdly, as I've already mentioned, concurrent or spectral masking is a real, very strong effect which among other things does helpful thinks like make perceptual coding or lossy compression actually work against pretty long odds. Interested parties should read the articles on masking and critical bands on Wikipedia for starters.

So, thirdly, if a spectral line on a FFT falls below the masking curve for any stronger sound on the FFT, same answer.

At this point, I've shown why just about every spectral line but the those due to the test signals themselves on every test report describing jitter in some piece of audio gear isn't going to be heard.
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