The Well Tempered Master Clock - Building a low phase noise/jitter crystal oscillator

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When Andrea started this I supported it even though I was very skeptical of the close in phase noise claims. I was interested in how successful he would be in making a high performance oscillator. In some senses he has been successful. We did not get to learn a lot from his efforts (like how to optimize a Driscoll oscillator or understand crystal specs). (I have a crystal parameter meter and got no input on how to use what it tells me.) Still he seems to have succeeded in making high performance oscillators within certain limits. They are not space grade and not stable enough for GSM but fine for audio.

The problems with comparing to alternative packaged oscillators or even other discrete efforts are the variety of uncontrolled effects when changing. Everything from isolation from loading of the oscillators to EMI/RFI are not being checked for or controlled so its difficult to ascribe the perceived improvement to one aspect. And then a real blind test of any sort is difficult as well.

As for the audio stuff I'm still really skeptical given the worship of analog playback that is orders of magnitude worse in "close in phase noise" effects. You would think analog is unlistenable given how much worse it is.

The only real testing of jitter that has been published suggested thresholds orders of magnitude higher than any decent packaged oscillator.

I'm all in favor of improving anything that has been shown to contribute to better sound but, for example, digital audio has a fundamental digitally defined performance floor. The only way to break through that limit seems to be more bits (not practical) or dither. I have heard of efforts to modulate the clock to add dither and maybe that is happening here. What is missing are any measurements of the analog outputs showing differences between the various clocks.

I stopped focusing on the clocks and switched attention to getting that clocking to the DAC/ADC as cleanly as possible. Its much more difficult than it first seems. Any ground noise coupling back, supply noise cross coupling moving the switching threshold etc. and then load modulation from internal data processing affecting the switching will compromise the overall results.

And there is a real problem when judging your own work, or that of others, in separating your personal investment into the work. If it makes you happier with the results that's great. But its not a guarantee that its a universal truth.
 
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