Author Topic: They still don't get it..........  (Read 3097 times)

Gen. Dreedle

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They still don't get it..........
« on: December 09, 2010, 05:02:40 PM »
http://www.diyaudio.com/forums/digital-source/178173-rubidium-clock.html

One major point, that seems to get overlooked in all of these discussion on jitter................

The famous "2 nSec is the limit of audibility" only applies to:

Jitter, when the frequency is the word clock frequency. Which is why a lot of folks believe it is a few pSec. Because those folks measure at bit clock frequency. (Yes, clock designer types measure at the actual frequency of the clock, not what it is, after it is divided by 256.)

What is so hard to understand about that? Obviously, a lot. Because no one ever points that out. So, when some git like me claims they can make a clock, that only has a few pSec of jitter, and it kicks butt, the usual crowd (no, not the J. J. Hooter crowd, as they are off on some other tangent), disputes that makes any difference.

(It does! So, deal with it.)

And the second point, which one person seems to be aware of, is that it also applies to Gaussian jitter. When you add a degree of deterministic (data-correlated) jitter, the threshold goes down.

Which is why SPDIF sucks. Even the gang at Greaser's Palace know that!

I don't want to have to 'splain this again.

So, between guys who think a rubidium standard, phase-locked to a multiple of 44.1 kHz, is a great idea, who are as clueless as the Chinese "We have much better quality 1 ppm accuracy! Make sound much better since no jitter!" parrots, it is no wonder I have to 'splain this. Again.

(I actually had one guy, who should know better, told me that Brand X clock is only good for y ppm, so if you invert that, you get an approximation of what jitter range is. And he was serious!!!!!!!!!!!!!!!!!!!)
"Major Danby, sir."
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MystereoN

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Re: They still don't get it..........
« Reply #1 on: December 11, 2010, 12:44:49 AM »
Yes, Chinese are very interesting. They are claiming "1 ppm accuracy and no jitter" but on the other side they are feeding their clocks with >100mV ripples  :o
Still 1 ppm accuracy and no jitter?



And no, no long ground loop on scope probe to pick up RF.
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MystereoN

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Re: They still don't get it..........
« Reply #2 on: December 12, 2010, 10:17:29 AM »
But all this is benign stuff, and here is malign stuff.
Never argue with a fool,
they will drag you down to their level,
then beat you with their experience!!!

seagreen

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Re: They still don't get it..........
« Reply #3 on: December 12, 2010, 03:06:36 PM »
It seems cables are the problem everywhere, doesn't it?
No double blind testing was used in the making of this post.