Asynchronous I2S FIFO project, an ultimate weapon to fight the jitter - Page 12 - diyAudio
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Old 27th September 2011, 04:29 AM   #111
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Hi Ian,
Very nicely done board!
I was a bit skeptical about the o-ring suspension design for the clock board, until I saw something similar in an HP 8662A signal generator, which has been used as a low phase-noise reference for many years. I was working on a fix-upper for the past two weeks. Very solid machine. My unit is apparently aged and has multiple problems. But it is fun to work on and eventually bring it back to life (and to spec later).

BR,
simmconn
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Old 27th September 2011, 01:22 PM   #112
Bunpei is offline Bunpei  Japan
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Quote:
Originally Posted by iancanada View Post
1. ... I attached the phase noise plot of this buffer just for reference.
How nice to have such a plot! How did you obtain this ? Did you measure it by yourself? Which instrument did they use?
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Old 27th September 2011, 01:54 PM   #113
GOR3 is offline GOR3  United States
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Ian,
You are an artist.
Regards,
George
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Old 27th September 2011, 02:06 PM   #114
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Quote:
Originally Posted by Bunpei View Post
How nice to have such a plot! How did you obtain this ? Did you measure it by yourself? Which instrument did they use?
Hi Bunpei,
I hope I had that oscillator, if so, that would be one of my dream oscs .
This phase noise plot was originally from the manufacturer of the clock fanout buffer . There are two curves, one of them is for the input clock and the other one is for the output clock from the fanout buffer . The second one is very close to the first, that indicates the additive jitter of the fanout buffer is very small (29fs). Usually they use equipments like Agilent E5052A making this kind of measurement. Ian
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Old 27th September 2011, 02:22 PM   #115
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Quote:
Originally Posted by GOR3 View Post
Ian,
You are an artist.
Regards,
George
Thanks George,
Technologies is a kind of art, especially for our audiophiles .
Best Regards,
Ian
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Old 27th September 2011, 05:56 PM   #116
2A3SET is offline 2A3SET  Canada
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Default shunt for XO

9uV, is that ADP-151? A shunt reg (like TPA trident or salas) sounds better with XO.


2. Powering two oscillators at same time with 9uV RMS low noise high PSRR LDO and independent EMI suppression filters.

Last edited by 2A3SET; 27th September 2011 at 06:05 PM.
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Old 27th September 2011, 06:17 PM   #117
1audio is offline 1audio  United States
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Why would a shunt regulator sound better running a crystal oscillator? The key issue with an XO is low noise. Number two would be high isolation from the primary supply to prevent modulation from external sources like the audio/data stream. A good XO will have zero dynamics as a load. I supplied a regulator above with 20 dB lower noise than any I have seen published. It could be folded into a shunt regulator but that may make no difference except for requiring some really sophisticated current source to get to the same place.
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Old 27th September 2011, 06:24 PM   #118
2A3SET is offline 2A3SET  Canada
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A shunt without a CCS should be good (like TPA trident). I think it may due to the extra low impedence of shunt reg. My experience is limited to a dual rate XO (Silab 532).
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Old 27th September 2011, 06:32 PM   #119
1audio is offline 1audio  United States
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Ian:
What are you using for the clock buffer?

Making a measurement of the phase noise is not trivial but is not too hard to do with pretty available stuff. For a buffer you only need one oscillator, a suitable rf mixer and a good fft. Its tedious to setup and calibrate. For an audio system its easier to look at the spurious outputs on the audio outputs, less hardware is needed and it will show the effects of everything in the chain.
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Old 27th September 2011, 10:39 PM   #120
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Quote:
Originally Posted by simmconn View Post
Hi Ian,
Very nicely done board!
I was a bit skeptical about the o-ring suspension design for the clock board, until I saw something similar in an HP 8662A signal generator, which has been used as a low phase-noise reference for many years.BR,
simmconn
Thanks simmconn,
Did you fix up your super oscillator? Please just let me know what it sounds like .
At least two things are sensitive to the mechanical vibration. One is the crystal inside the XO and the other is the MLCC due to its piezoelectric effect. So, theoretically the rubber ring works for isolating that vibration. But, by how much, I didn't confirm.
Regards,
Ian
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