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The Well Tempered Master Clock - Building a low phase noise/jitter crystal oscillator
The Well Tempered Master Clock - Building a low phase noise/jitter crystal oscillator
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Old 10th September 2014, 11:01 PM   #11
andrea_mori is offline andrea_mori  Italy
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The Well Tempered Master Clock - Building a low phase noise/jitter crystal oscillator
Here attached the part list to build the oscillator.

Some components have a notation indicating that they have to be selected depending on clock frequency, used outputs, output voltage.
R2 has to be adjusted to set the right current flowing through the jfet.

I recommend to use the Laptech custom crystal, or a similar type with the same specs (be careful to select a heavy polished crystal!).
Anyway, if you own the right gear to select the crystal, you can try to get a bag of crystals from the shelf and select the best by measurement.
You can also select the best, comparing the crystals from the bag with several listening sessions, if you have the patience to do the job.

As the power supply, I'm using the Tentlabs shunt regulators.
The first has to be selected for 15V, while the second has to be choose for the desired output voltage, 5V or 3.3V.
You can use other regulators, but I suggest to get a low noise regulator, preferably a shunt type. With a noisy regulator you can loose several dB in phase noise.
Anyway, the PCB is able to accommodate 3 terminal regulators, if you like to build a cheaper version of the oscillator.
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File Type: pdf TWTMC-C_Part_List.pdf (34.0 KB, 397 views)
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Old 10th September 2014, 11:40 PM   #12
kevinkr is offline kevinkr  United States
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The Well Tempered Master Clock - Building a low phase noise/jitter crystal oscillator
Very interesting thread, thanks for sharing the project with us. I will be watching and hope to build one based on your work at some point.
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Old 11th September 2014, 08:09 AM   #13
andrea_mori is offline andrea_mori  Italy
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The Well Tempered Master Clock - Building a low phase noise/jitter crystal oscillator
Thanks Kevin,

I'm pleased to share my experience with the community.

A little off topic: next May I will be in Boston, what location/hotel do you suggest?

Andrea
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Old 11th September 2014, 01:24 PM   #14
Eldam is offline Eldam  France
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Hi Andrea,

(a hotel at Lynnfield to visit Boston Acoustic factory ! )

Could you sell me one of your second choice (after selection sort out measurements) 11.XXX Laptech for a swap in one of my AYA2 or Distinction-1541 ? PM me please to know if we can find a money agrement if you don't use those second quality crystals after sort out, maybe it can be good enough for me and the quality I target in relation to the money I can put in it !

Of course If you think it worth it : (if a second choice with Laptech can perform better than a 2 dollars NDK e.g. ?)

Is phase of the crystals is affected by the quality of the PS noise ? What sort of PS design can you advise for us : recent low noise regulator of TI or Micrel ? your shematic with a watch cell ?
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Old 11th September 2014, 01:55 PM   #15
andrea_mori is offline andrea_mori  Italy
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The Well Tempered Master Clock - Building a low phase noise/jitter crystal oscillator
Quote:
Originally Posted by Eldam View Post
Hi Andrea,

(a hotel at Lynnfield to visit Boston Acoustic factory ! )

Could you sell me one of your second choice (after selection sort out measurements) 11.XXX Laptech for a swap in one of my AYA2 or Distinction-1541 ? PM me please to know if we can find a money agrement if you don't use those second quality crystals after sort out, maybe it can be good enough for me and the quality I target in relation to the money I can put in it !

Of course If you think it worth it : (if a second choice with Laptech can perform better than a 2 dollars NDK e.g. ?)

Is phase of the crystals is affected by the quality of the PS noise ? What sort of PS design can you advise for us : recent low noise regulator of TI or Micrel ? your shematic with a watch cell ?
Hi Eldam,

Laptech did not send me the crystals that did not match the specs. They sent me 5 crystals only (minimum orderable quantity), within the specs.
If there will be enough interest to place a new order, I will inquiry Laptech about the cost of the second choice.

As I said above, the Laptech crystal is the starting point of this project, for its superior performance and, above all, its manufacturing repeatability.
Anyway, you can use any crystal you want in the Clapp oscillator. The advantage of using the Laptech one is that you know exactly what you can expect, while with other crystals the results are uncertain.
The choice of a good crystal is not a problem of this specific oscillator, it's a general issue in any oscillator.

About the PS, a noisy regulator can heavily influence the performance in phase noise close to the carrier, so I suggest a good PS, better the shunt type.
I think the Ti or the Micrel could be suitable, but I have never tried them.
I'm developing a low noise shunt regulator, cheaper that the Tentalabs, but my times, as you know, are usually long.

Andrea
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Old 11th September 2014, 02:06 PM   #16
kevinkr is offline kevinkr  United States
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The Well Tempered Master Clock - Building a low phase noise/jitter crystal oscillator
Quote:
Originally Posted by andrea_mori View Post
Thanks Kevin,

I'm pleased to share my experience with the community.

A little off topic: next May I will be in Boston, what location/hotel do you suggest?

Andrea

Hi Andrea,
There are a lot, in the heart of Boston I would probably recommend the Marriott Longwharf.. Boston is expensive, not quite as bad as NYC, but up there. I am a comparatively short subway ride away if you wanted to combine some audio with your trip..
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Old 11th September 2014, 02:06 PM   #17
merlin el mago is offline merlin el mago
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Forza Andrea thanks to share your work.
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Old 11th September 2014, 02:56 PM   #18
andrea_mori is offline andrea_mori  Italy
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The Well Tempered Master Clock - Building a low phase noise/jitter crystal oscillator
Quote:
Originally Posted by kevinkr View Post
Hi Andrea,
There are a lot, in the heart of Boston I would probably recommend the Marriott Longwharf.. Boston is expensive, not quite as bad as NYC, but up there. I am a comparatively short subway ride away if you wanted to combine some audio with your trip..
Kevin,
very glad to combine Boston's life with "Boston's audio"
I will stay there 4 days, probably from April 30th to May 3rd, then I'll go to New Orleans.
I'll let you know, so we could combine a listening session.

Thanks
Andrea
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Old 11th September 2014, 03:01 PM   #19
kevinkr is offline kevinkr  United States
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The Well Tempered Master Clock - Building a low phase noise/jitter crystal oscillator
Excellent, looking forward to it!
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Old 11th September 2014, 04:06 PM   #20
Eldam is offline Eldam  France
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Thank you Andrea for explanations, it's clearer for me.

Could you please PM me the price of one laptech please ? Have you one of 11.xxx you don't use ?
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