Asynchronous I2S FIFO project, an ultimate weapon to fight the jitter - Page 196 - diyAudio
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Old 6th January 2013, 01:18 PM   #1951
percy is offline percy  United States
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Quote:
Originally Posted by iancanada View Post
Test3: WM8805 output SCK jitter
...
Test4: SCK jitter after FIFO
Great! Did you by any chance happen to catch the spectral content of the jitter in both cases ? Was it random ? or periodic ? In band ? Out of band ?
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Old 7th January 2013, 02:19 AM   #1952
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Quote:
Originally Posted by glt View Post
Ian, very nice Results!

Do you think you can do better than 5 ps RMS? Isn't the jitter dominated by the flip flop?
Both CCHD957 and Si570 show less then 5ps RMS jitter on my scope, some times they can go below 4ps after long time run in. But I couldn't tell how good they are because of the 2ps jitter floor and other factors. Actually testing on a good clock is very difficult. But on a bad one is very easy.

Quote:
Originally Posted by glt View Post
I've never seen jitter specs for flip flops, just people saying figures here and there with figures higher than jitter values of clocks.
flip-flop does add jitter to the secondary generation clock which is the output of the flip-flop. But not as much as I thought. Remember a RF engineer mentioned it add 6dB on phase noise each time going through a flip-flop. By figuring out from the added jitter number, I roughly estimated, on time domain, it adds no more than 1ps additive jitter reference to the father clock if using a decent flip-flop fast than 200Mhz with good power decoupling.

But the driving current and the load will make some change to the number.

To get more accuracy result, higher grade scope is required, such as 10G bandwidth with jitter package, or a signal analyzer.

Regards,

Ian
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Old 7th January 2013, 09:14 AM   #1953
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Quote:
To get more accuracy result, higher grade scope is required, such as 10G bandwidth with jitter package,
What you need for more accuracy with you scope i describe in previous post. High bandwidth is not needed for jitter measurement (for audio equipment) at all.

PS And wm8804 MCLK output not designet to work on 50ohm load.
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Last edited by Nazar_lv; 7th January 2013 at 09:17 AM.
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Old 7th January 2013, 09:18 AM   #1954
TNT is offline TNT  Sweden
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Ian, Your previous measurement with the generic 11.2896MHz XO showed jitter RMS to be 5.13 ps. Above, You state that with Si570 show less then 5ps and some times they can go below 4ps.

This does not seem like a big diff!? Or is Your measurement rig exhausted?

Can You do spectrum analysis?

A measurement comparing s/pdif in with s/pdif out using Your s/pdif board would be very interesting.

Really enjoying the sound coming out with the generic clock :-) - "stability" kind of summarize it. (fed by a SB Touch)

/
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Old 7th January 2013, 09:48 AM   #1955
qusp is offline qusp  Australia
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come on man, keep up did you read the post that contained that measurement or any of the subsequent posts? hell even the post those numbers were in. the measurement rig has a 2ps noise floor, so predictably the si570 has ~1.5-2ps jitter as expected plus the output buffer (or maybe with, Ian may clarify that if the output clock buffer on the si570 board was included in that measurement

I dont know what you would expect to learn from a spdif in and out comparison. the spdif TX will completely dominate the jitter, telling almost nothing about the fifo

Last edited by qusp; 7th January 2013 at 09:51 AM.
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Old 7th January 2013, 11:30 AM   #1956
marce is offline marce  United Kingdom
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marce, you watching mate? not bad eh?
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Old 7th January 2013, 12:40 PM   #1957
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OK qusp... but Ians statement about that he sometimes see 4 ps is unclear wrt if this is the meas rig in extra good condition or a happy moment for the DUT. Really, I'm trying to understand the difference between the si570 and the generic osc I'm listening to (ok, via s/pdif!) now.

I'm just curious what I'm feeding my DAC with, thats all.

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Old 7th January 2013, 12:45 PM   #1958
TNT is offline TNT  Sweden
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Originally Posted by TNT View Post
OK qusp... but Ians statement about that he sometimes see 4 ps is unclear wrt if this is the meas rig in extra good condition or a happy moment for the DUT. Really, I'm trying to understand the difference between the si570 and the generic osc I'm listening to (ok, via s/pdif!) now.

I'm just curious what I'm feeding my DAC with, thats all.

/
Using s/pdif, I could probably not make use of a si570 based clock board...

But I'm planning to build me a new DAC. I would like a simple, balanced out 2 channel, ESS based with their dig. level control.

The question is just which one?

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Old 7th January 2013, 01:27 PM   #1959
qusp is offline qusp  Australia
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yeah if just using spdif, forget the si570, just stick a crystek in the clock board and be happy. the main benefits of the si570 are covering the full range of sample rates from 44.1->384 with nice low jitter as well as clean way to drive dual mono dacs.

he simply meant it measures 5ps but sometimes 4ps, maybe environmental or even thermal noise was higher when he got 5ps, but I think it has to be the si570 board in total, so that means the jitter is made up of 2ps noise floor plus the si570, plus the clock buffer. so I think its pretty much to spec, 1.5-2ps maybe lower for the si570 itself.

but one things for sure, these generic XOs are a surprise, totally useless for my purposes, but jeez not bad at all if you are playing 44.1
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Old 7th January 2013, 06:32 PM   #1960
TNT is offline TNT  Sweden
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Ian!

I sit here and enjoy the best sound I have ever had in my system. It improved even more after I took the leap and robbed my aTV from it's Toslink cable, exchanged the connection between the SB and your fifo. The cable change was inspired from one of your pictures of your DAC setup and it makes perfect sense with the fifo. I'm still on 44,1 and s/pdif but I have to say my system sounds lovely.

I just played Chopin, Krystian Zimerman ‎– 4 Balladen • Barcarolle • Fantasie (DG 00289 477 9198)...

thanks and hats off Ian!

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