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PostPosted: Tue Jul 15, 2008 4:51 pm 
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Guys,

It's actually hard to present jitter numbers using the methods we all use to measure jitter. The sideband method and calculations fluctuate so much that a clean number is hard to come by. Only Paul Miller is willing to address this. In several emails I had with Paul on his methods and JA's I can only say that averaging over long periods is still only going to give you a reference and not what I would call an accuate method.

I am doing some jitter testing on 24 bit dac modules I created today. In the Prism world they basically send a -20dB 10k signal at any bit depth you want and look at the spectral data, thd and such to get an relative idea if you are heading in the right direction. Ap does basically the same thing but you have to play test tracks in either a cd transport or computer. With the Prism it can output direct and assign any computer audio device to the osscillator.

Thanks
Gordon

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PostPosted: Sun Jul 20, 2008 9:05 am 
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How long ago was that? Could't they have acquired new test gear like Miller's audio QC suite or something?

I feel that we should first get the facts straight before we go putting people or magazines in the corner like this.

Somehow these guys measured 5ps of jitter if you like it or not, and that you don't do with a multimeter.
So they DO have access to something or someone that actually had the stuff and knew how to operate it...


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PostPosted: Sun Jul 20, 2008 10:18 pm 
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You didn't understand.

The other magazine, namely Stereophile, has measured 406ps for the same unit. We do know the way the Stereophile measures the jitter, but we don't know what Hifi World, which announced 5ps, does.

If you can, please shed some light on their measurement method, and we'll be all smart enough to draw our own conclusions. Other wise...... cool down, bub.


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PostPosted: Mon Jul 21, 2008 12:14 am 
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Sorry Pedja but did you already post a constructive comment?


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PostPosted: Mon Jul 21, 2008 9:14 am 
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He just did.

Claiming 5 ps or 400 ps of jitter is completely meaningless without the bandwidth
of the measurement.

This is just like "My car makes 75 miles and yours only 3".
per minute? per hour? per gallon?

Or like MTBFs without activation energy. (often seen)

Gerhard

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PostPosted: Mon Jul 21, 2008 10:32 am 
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Using one review agains the other to dismiss one of them or "prove" one wrong... that's the opposite of constructive.
It is not helping anyone who is interested in the subject of this thread to a better understanding or a higher level of information, as well as doing no justice to the clear suggestion that there is something very low jittery going on here.

It is only spreading doubt by shopping selectively in magazine's reviews and deliberately putting one claim against the other as if they are contradictive, and, even worse, doing so while forgetting essential information which relates directly to the subject.
I call that misinformation and twisting.

It could have been ( at least a little) constructive if in the same post he would have quoted John Atkinson saying in the exact same review, in the exact same measurement sidebar, just one sentence further:

"Actual data related sidebands were much lower in level; if it weren't for the supply-related spuriae, the ProLogue Eight would have very good jitter rejection."

This is relevant. What if the Hifi-World review sample did not suffer from the hum in the same way that the Stereophile review sample did? It suggests that the "lowest jitter we have ever measured" claim in Hifi-World very well can and does make sense.

I agree that the HFW measuring method is not known and there is some data missing for us to compare the figures, but the two magazines are certainly not contradictive.

On a last note, the comments on the sound quality from all reviews like TAS, Stereophile, Hifi-World, Music&Emotion, Stereoplay and some other European mags, are so consistently positive especially in the areas where Jitter is often the major spoiler, I'd say there is something going on here worth investigating furter.


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PostPosted: Mon Jul 21, 2008 4:38 pm 
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marconi wrote:
Using one review agains the other to dismiss one of them or "prove" one wrong... that's the opposite of constructive.
It is not helping anyone who is interested in the subject of this thread to a better understanding or a higher level of information, as well as doing no justice to the clear suggestion that there is something very low jittery going on here.


A higher level of information would only be possible if we could get all the information needed.
As we can't, it ends up in speculations.
Which is what we are doing, and what you are doing too.
Anyway that you look at it, you are speculating too.
It's not a question of being constructive or not, but some of those who have posted in this thread are just being rationale.

There should not be any blind faith when discussing reviews, measurements, or even how it sounds.
The market is full of gear that most mags rave about and when you go to listen, you don't like it. It has happened to me on several occasions.

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PostPosted: Mon Jul 21, 2008 5:45 pm 
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On the contrary, being constructive is the whole issue.
What's the point of a forum if the intent is not to be constructive? Rational one can only be if (s)he has facts. Since apparently none of the people being active in this thread has ever had any hands-on experience with the SuperTubeClock, rationale is still miles away. Nobody can be rational here until he or she has actually thorouhgly investigated the subject, on a test bench, and reported his or her findings.

"All the information needed", sure who doesn't want that? But for the time being we apparently do not have "all the information", and we'll have to do with whatever is available. This inevitably leads to speculation, but who cares, even speculation can be constructive as long as it is backed up by at least a little bit of decent thinking, based on circumstantial evidence, as in bits of information coming from sources available to all.
The sort that is being presented here, for instance.

But in my view it should not be containing dismissive messages based on what is ultimately a total lack of knowledge about the product which was and actually still is the original subject of this thread. Especially not in the way where two bits of information from two different magazines are deliberately moved in opposition to each other with the help of a tactical omission, and truth is the victim.

Finally, when you don't like a piece of equipment which received a rave review in one of the mags, don't blame the magazine or the reviewer. Don't go searching for stones in incomplete technical information in "measurement" sidebars, and say "so there, you see?". Question it, but don't use it the way that you would use more comprehensive and complete technical info, as a weapon in a discussion.
Investigate why it disappoints you, search for the rationale. Is it really such a disappointing piece of equipment or did it just not combine very well with the surrounding stuff?
Will there be circumstances that it will perform conform the review, and did I miss out on that? Did I try hard enough to make the product perform conform the review?

So the question is here: have you listened to the PL8 already ? If not, your suggestion is out of line.

How many times was a rave review of an audio product in a magazine confirmed by your own listening experiences?
And how many different opinions about that product exist outside of your own's?
So who is right then?


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PostPosted: Mon Jul 21, 2008 8:02 pm 
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marconi wrote:
So the question is here: have you listened to the PL8 already ? If not, your suggestion is out of line.


What suggestion?
Aren't you out of line too?

marconi wrote:
How many times was a rave review of an audio product in a magazine confirmed by your own listening experiences?
And how many different opinions about that product exist outside of your own's?
So who is right then?


If I don't like it, I'm right.
If I like it, I'm right.
Get it?
If you take a part of your hard sweated money to buy something, don't you have the right to listen, judge for yourself and like it or dislike it, even if it goes against what is "established"?
Jeez...
I've seen too many disatisfied "audiophiles" that had spent a fortune and never get it right. Probably by thinking as you do.
Reviews are entertaining reading (some...) but what do I care it it has 4 or 5 stars or if it has class A rating or whatever?
Some get it right, some get it wrong, but that's life.

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"Any intelligent fool can make things bigger, more complex, and more violent. It takes a touch of genius - and a lot of courage - to move in the opposite direction." Albert Einstein


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PostPosted: Mon Jul 21, 2008 8:37 pm 
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Agreed. If you like it, you like it. If you don't, you don't.

However:
If you don't like it but others do, then they are as right as you are.
And on the same level your definition of "right" does not dismiss the verdict of magazines.


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PostPosted: Mon Jul 21, 2008 10:20 pm 
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Mr. Marconi - - this thread seems to consist entirely of some very knowledgeable clock designers asking for basic information on your product, and you refusing to provide any such information.

Except a couple of magazine reviews which seem to indicate, taken as a whole, that your product is the weak link in an otherwise well regarded DAC.

If you care to enlighten us as to how this thing works, how it solves the noise and supply problems inherent in such a topology, then perhaps this can return to a reasonable discussion. However, at the moment this is vapourware, and I'm afraid you're the source of the vapour.


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PostPosted: Tue Jul 22, 2008 12:31 am 
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Quote:
Mr. Marconi - - this thread seems to consist entirely of some very knowledgeable clock designers asking for basic information on your product, and you refusing to provide any such information.


Thank you for bringing this discussion back to technical level, and to the level of a reasonable discussion.

However I'd like, for my understanding, to clear up some inconsistencies in your text:
"entirely" and "some":
I invite you to elaborate on the statement that all of the posters are {some} very knowledgeable clock designers.
I'd really welcome to see what clocks they have designed, in which products they appear, and how they fare against the product that started this thread.

How it works: basic information is readily available, even in this thread. An oscillator tube, and a fast comparator.
The noise in this clock is largely dependent on the noise generation of the tube used. It is a specifically low noise VHF oscillator tube, especially low in noise in the LF region, and selected as such to be quite suitable for its task.
Power supply noise is suppressed by a simple combination of a regulator, followed by a resistor and capacitor, to form a 6dB/oct filter at a very low corner frequency. No tricks there, but effective. Since the current draw of the oscillator is essentially constant, this is quite straightforward.
But that's not what makes up a good clock. A good clock has several properties that it has to obey to. These have largely been obtained by proper layout, we are talking 2ns rise times here. We do not want overshoot, ringing, saturation and problematic recovery, or ground bounce. That are things that count.

Quote:
...noise and supply problems inherent in such a topology

Please elaborate. What is so specific in "such" -what do you mean with such- "a topology"?
Are you aware of the noise sources in a CMOS oscillator (still used by 90% in the business)? And the jitter it consequently generates? And can you put that against a tube oscillator and draw educated conclusions from that? That alone should tell you something.

I agree only partly with your qualification of "vapourware" because the discussion has -at least from the side of quite a lot of posters- always centered around disqualifications solely based on assumptions and prejudice. That's where the vapour is.
From my side however I have only reacted on these disqualifications by shooting holes in inconsistent reasonings and unfounded, unbackedup and out-of-the-blue negative comments, without faulting myself into making outrageous statements, if any at all.

My point of view is that everybody who ventilates an opinion in this forum about this product should back his or her opinion up by either thoroughly testing the product itself, or try and build a similar clock and find out what it is doing or doing wrong. It ain't that difficult for your esteemed "very knowledgeable clock designers", if they know how to do RF layouting and know how to avoid pitfalls like parasitic inductances, capacitances and impedances.

And there is the problem:
No one in this forum has tested this clock.
No one in this forum has tried to build something similar to mimic the behaviour of this clock, and investigate its behaviour. Or at least, he has not come forth with this.
The conclusion can only be that this means that all the comments ventilated in this thread are uninformed and obviously biased against the possibility that a tube can be a good oscillator for a decent audio clock.

As for the magazines: no magazine that I know of has indicated this clock as the weak link, not even in "an otherwise well regarded DAC". Please specify, I'm not aware.
What do you mean by "taken as a whole"?

Furthermore, the expression "a couple of magazines" suggests that you do not take them seriously, just for the sake of argument in this discussion. That's not totally fair in a discussion like this. We're talking the world's leading magazines here. Do you know better? And if so, from what authority?
You certainly have not tried this clock, or have you?

Anyway, thanks for your input and helping put this discussion back on its feet.


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PostPosted: Tue Jul 22, 2008 1:09 am 
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So we are actually honored by presence of this clock designer, who for some reason didn't introduce himself?!

Which simplifies all this...

So... cut that crap and let us know the actual jitter performance of your clock, please. We've heard you "it is low", but we ask "how much?". Your chance to get famous. As simple as that.


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PostPosted: Tue Jul 22, 2008 4:23 am 
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So, if you really are the guy who designed this silly thing, then why are wasting your time on some obscure hobbyist forum???

Just because there are a handful of established high-end guys who hang out here.....................

(Hint: we aren't here to hawk our wares. OK, I may sell some surplus PCBs on occasion. Big difference from selling units that cost $$$$$$, with nothing to justify it other than my bloviating.)

It is not my job to explain why this is a silly idea. If you think otherwise, the burden of proof is on you.

And no, I have no intentions of discussing what commercial work that I have done. This is a hobbyist forum, and not a subject for discussion here. (Or anywhere else, as far as I am concerned. You can ask, but an answer will not be forthcoming. My clients are and will remain confidential.)

Nor is it an outlook for ego gratification.

Jocko


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PostPosted: Tue Jul 22, 2008 4:33 am 
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You wrote this earlier:

"This means the clock is VERY fast, leaving very little time to introduce jitter and noise............"

Very Fast as in very fast rise times and fall times.

Why? Finite rise times introduce "decision moment" inaccuracies. In your DAC, ADC, SRC. Decision inaccuracies are timing errors, is jitter.


First, you need to have an oscillator. Sine wave. Then, you turn it into a square wave.

Now, you wanna 'splain to us how a tube has lower 1/f noise than a low-noise BJT?????? Sorry, bub, we ain't buyin' it.

Then, there are other issues.............power supply noise, resonator Q.............you know, stuff like that. The stuff that determines the phase noise floor of the oscillator. You have to have a handle on that before you worry about how much uncertainty you generate when you convert it into a square wave. Then you can talk down to us in condescending terms.

Jocko


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