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Author Topic: They're talking about jitter......................  (Read 8870 times)

Gen. Dreedle

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Re: They're talking about jitter......................
« Reply #30 on: September 03, 2016, 11:56:55 AM »
Quote
For the lowest "jitter" you need to go for the fastest logic, preferably 74AC series.

SERIOUSLY!!??!!??

I guess I am going to have to find some plots, of SC-cut crystal oscillators, made with cheap ol' TI LVC chips.

IOW, an unbuffered 04. Followed by a second one, to isolate it from the world.

Oh, and working at ROOM TEMPERATURE.

Oy vey....................they all seem to get more stupid by the day........................
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MystereoN

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Re: They're talking about jitter......................
« Reply #31 on: September 04, 2016, 03:30:18 PM »
 ;D

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Gen. Dreedle

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Re: They're talking about jitter......................
« Reply #32 on: September 09, 2016, 01:01:32 PM »
"Who is this man?"

Quote
I mentioned a while ago that I saw some measurements on the AT vs SC crystals.
They did not differ at close-to-carrier offset frequencies.

Very roughly:
the close-in PN is much more dependent on the ESR of the xtal, as this dictates the xtal self-noise.
Strangely not the Q of the xtal so much.

Here, the SC xtals are almost 10 times worse.

The close-in PN can be improved by increasing the current through the xtal (the Drive Level) and using AT cut xtals for their much lower ESR.
Both of which has been adressed in the RutgerS oscillator.

I seriously doubt that RutgerS oscillator's excellent performance at < 100 Hz will be improved upon by using SC-cut xtals.
Neither is it trivial to design a ”proper” mode-surpressor for SC based oscillators.

"Take him out, and............................."
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Gen. Dreedle

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Re: They're talking about jitter......................
« Reply #33 on: September 09, 2016, 01:03:12 PM »
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can we draw any information about close in noise from ADEV measurements? I would think that there would be a good correlation but maybe i'm missing something. I would prefer than since I'm setup for ADEV.


YES! YES! YES! YES!

Time to earn that big consulting fee, bub.

Only don't ask me what the correlation is, since my measurements are obviously bogus.

Have a nice day.
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Gen. Dreedle

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Re: They're talking about jitter......................
« Reply #34 on: September 09, 2016, 01:04:51 PM »
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At lower f even SC-cut xtals operate at fundamental-mode.
For each additional overtone mode, the ESR increases.

Yeah, someone may need to put him out of his misery.
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Gen. Dreedle

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Re: They're talking about jitter......................
« Reply #35 on: September 09, 2016, 01:12:10 PM »
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Phase noise is short term variations in frequency. 'Close in " phase noise really is longer term variations in frequency. The region in question here seems to be in the 1 second to 100 Hz range, which is also the most difficult to measure.

Well, it is if you are not using the right gear. IOW, some DIY gizmo is not going to cut it. (We gave up on that approach, around 15 years ago.)

Then, there is that ADEV............................

Quote
And still finding a way to genuinely attribute sonic benefits in blind testing is needed. The current lit indicates that the audibility threshold is way higher than any of this stuff, whether for wow and flutter or for jitter.

Part of the challenge is confirming that the sonic difference is from the phase noise and not some other incidental change that could be significant.

Blah, blah, blah, blah, blah...................

I could 'splain it to you, but since my measurements are crap, and I am not published in some stupid "peer reviewed" (by idiot professors) journal, yeah, everything I have done will get ridiculed, so what is the point of 'splaining it.

Good luck continuing to flounder on the beach....................
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Gen. Dreedle

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Re: They're talking about jitter......................
« Reply #36 on: September 09, 2016, 01:16:13 PM »
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Obviously, I look forward to measure the phase noise of all the oscillators to confirm the listening impressions, but at this moment I can't afford an Agilent E5052, so I have to wait until I will access the University Lab to do the measurement. In the meantime I will try to get the suitable stuff to do the JTest.

Oh, poor baby......................

If you didn't slag off the only person with the gear and knowledge of this stuff...................

But, you did. You know more than me. Sod off!

Have a nice day.
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Gen. Dreedle

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Re: They're talking about jitter......................
« Reply #37 on: September 09, 2016, 01:21:47 PM »
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i know this is a high end design, but maybe there is a ''budget'' oscillator available that would be cheaper than the commercial ones (like the popular crystek's or ndk's) that would perform better than these and ''give a taste''....?

Good question. Might be hope for this lad.

Actually................no!

If there was, you-know-who would be building them, and selling them.

To manufacturers. Not cheap-@$$ DIYers.

BTW, the Craptek 22/24 ones...................can anyone 'splain why they have the same phase as the 45/49 ones?

Anyone see anything wrong with that?  Hmmmm........................?

BTW, don't expect them to meet spec, because a lot don't.

Which ones are more likely to meet spec................exceed spec...............not meet spec......................etc.

Yeah, guess who knows that answer. It will cost you $$$$$ to find out.

You can find out where to send PayPal donations...............................
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Gen. Dreedle

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Re: They're talking about jitter......................
« Reply #38 on: September 09, 2016, 01:23:05 PM »
Quote
Vibration can easily induce high levels of "close-in" noise on the oscillator output.

That is why I still remain slightly sceptic to the idea of close-in PN as being the single most mportant parameter for audio clocks.
In a listening room environment, all that hard work of lowering the close-in PN is wasted once the enclosure and the xtal start vibrating to the music.

Yet upgrading the clock seems to improve the percieved sound...

Can it be something else than just close-in PN??

Please, stop now....................................
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MystereoN

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Re: They're talking about jitter......................
« Reply #39 on: September 10, 2016, 02:53:38 PM »
Quote
BTW, the Craptek 22/24 ones...................can anyone 'splain why they have the same phase as the 45/49 ones?

Anyone see anything wrong with that?  Hmmmm........................?

45/49 should have 6dB worse noise figures as 22/24 ones ..... somebody is writting fairy tales in datasheet
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Gen. Dreedle

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Re: They're talking about jitter......................
« Reply #40 on: September 11, 2016, 04:00:59 PM »
Right........should be 6 dB difference.

Which really means....................the 22/24 ones are crap.

Also assumes the 45/49 ones meet spec.................

Ha, ha, ha!
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"Take him out and shoot him."
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MystereoN

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Re: They're talking about jitter......................
« Reply #41 on: September 11, 2016, 04:08:33 PM »
Ha ha
I don't care about Craptek, still running on 11.2896  :)
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Gen. Dreedle

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Re: They're talking about jitter......................
« Reply #42 on: September 11, 2016, 04:27:17 PM »
Yeah, but if you have a reel of NDKs, the right gear, a lot of spare time..............and a flip-flop......................you can use 22.whatever MHz.
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"Take him out and shoot him."
"Sir?"
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Gen. Dreedle

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Re: They're talking about jitter......................
« Reply #43 on: September 14, 2016, 12:37:51 PM »
Oh, crap....................they are back on the vibration crap..............again.

Yes, you truly are a Fluke of the Universe. We are laughing at you.

Give up.
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"Danby. D-A-N-B-Y."
"Take him out and shoot him."
"Sir?"
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MystereoN

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Re: They're talking about jitter......................
« Reply #44 on: September 15, 2016, 02:08:11 AM »
worrying about vibrations .... but don't worrying about using Craptek oscillators  ;D
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