[time-nuts] Re: Phase Noise Measurement in Dallas

[Thomas Tammann]

Thank you all! 

First and foremost, most people who actually heard comparison with different Ethernet setups agree that it sounds different. Technically, it does not make sense at the surface, zeros and ones are just that. But its not that simple. Nobody argues that the digital signal alters depending on a e.g. switch or shielded vs unshielded CAT6 cable. But the zeros and ones are only logical, not physical aka voltages...

Also, there is a huge gap between the “measuring is everything” crowd in audio and “hearing trumps everything” crowd. Both are wrong. The truth is somewhere in the middle and we try to figure out which measurements have actually an influence on audio and why. Bottom line, changes on all levels of the OSI model CAN have an influence in the resulting quality of the audio system.

Crystek vs my Symmetricom OCXO:
The producer of my switch says that the Crystek actually measures much better in real than on paper. He talks to the manufacturer and has insight knowledge.
The Symmetricom may or may NOT improve over the Crystek depending on the individual specimen and implementation.

Hence, my goal is to measure: I hope I would see 
114 at 1HZ and 140db at 10Hz. Not only would it confirm what I hear ;-) but also justifies the money I put down for a “preselected” (binned) specimen. Also, if I buy another clock with different phase noise and ADEV, I can hear for myself how much this makes a difference in real world audio pleasure vs upgrading eg a pre-amp….

But yes, in the meantime I learned a lot from you guys, thank you!!

Tom

PS:
If you wanna read how nerdy audio guys are ;-)
https://audiophilestyle.com/forums/topic/59419-master-clock-for-your-etherregen/ <https://audiophilestyle.com/forums/topic/59419-master-clock-for-your-etherregen/>
(A few guys would make great members of this mailing list ;-)

This guy is seriously interested to measure in oder to understand thinks he can hear but not explain
https://www-open--end--music-com.translate.goog/forum/privatforen/thomas-michael-rudolph-tmr/651284-messungen-von-ethernet-infrastruktur-switches-nur-lesen?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=de&_x_tr_pto=wapp <https://www-open--end--music-com.translate.goog/forum/privatforen/thomas-michael-rudolph-tmr/651284-messungen-von-ethernet-infrastruktur-switches-nur-lesen?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=de&_x_tr_pto=wapp>



> On Oct 27, 2022, at 12:39 PM, Chris Caudle via time-nuts <time-nuts at lists.febo.com> wrote:
> 
> On Wed, October 26, 2022 9:11 pm, Thomas Tammann wrote:
>> I use the OCXO on one of my specialized network switches
> ...
>> And yes, there are people out there claiming to measure the difference and
>> that these differences have an influence on sound. I guess the causality
>> is still hard to prove.
> 
> Yeah, the Ethernet clock is not related at all to the audio clock used in
> the D/A converter, even for synchronous audio-over-IP designs like Ravenna
> and Dante.  Consumer music players (as opposed to professional audio
> production equipment) do not even have a synchronized clock, they
> free-run.  Zero link between the Ethernet clock in the switch and audio
> quality. The quality of the clock to the digital-to-analog converter does
> influence quality, but again there is absolutely zero link between the
> Ethernet clock and the audio clock.
> 
>> Now the maker of this switch claims that an external clock has to have a
>> phase noise better than 125dB at 10Hz to make a difference.
> 
> According to that link you provided it does have a Crystek crystal
> oscillator, which is relatively low noise.
> You can see the specs here:
> https://www.crystek.com/crystal/spec-sheets/clock/CCHD-575.pdf
> 
>> I got likely scamed with my clock from China claiming 140dB @ 10Hz
> 
> If it is working well an ovenized SC cut oscillator should be able to
> reach that.
> 
>> hence, yes I want to measure it ;-) and I really just need to know the
>> phase noise (and Allen dev) at the actual output, no any converter. I hope
>> that makes all sense.
> 
> What you are attempting to do is understandable.  The entire premise
> behind it doesn't make sense from a technical standpoint, but the starting
> point is relatively straight forward, compare the phase noise spec of your
> surplus OCXO to the Crystek spec to make sure your new oscillator is
> better than the oscillator internal to the device.
> 
> -- 
> Chris C
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