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Old 3rd May 2009, 08:20 AM   #101
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Default Re: Graphs

Quote:
Originally posted by QSerraTico_Tico
I don't see much difference in the plots between the LCaudioXO3 and the 33.8688MHz Tent clock.
So?

mine is slightly better, compare prices and you'll have your answer
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Old 3rd May 2009, 08:34 AM   #102
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Default Re: Re: Graphs

Quote:
Originally posted by Guido Tent



mine is slightly better, compare prices and you'll have your answer
Actually I only compare sound.
I found the LCaudio a little bit better than the Tent in sound so I think these graphs ar not conclusive.
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Old 3rd May 2009, 08:49 AM   #103
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Default Re: Re: Re: Graphs

Quote:
Originally posted by QSerraTico_Tico


Actually I only compare sound.
I found the LCaudio a little bit better than the Tent in sound so I think these graphs ar not conclusive.

what you prefer soundwise does not have to be the best performing clock in terms of jitter

it depends what you are after, transparancy or euphonics
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Old 3rd May 2009, 11:22 AM   #104
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Question Re: Re: Re: Re: Graphs

Quote:
Originally posted by Guido Tent



what you prefer soundwise does not have to be the best performing clock in terms of jitter

it depends what you are after, transparancy or euphonics

I find transparency, or the lack of it, not a strong point of your clock. So I wonder why you bring that up.
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Old 3rd May 2009, 11:41 AM   #105
soongsc is offline soongsc  Taiwan
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Since we talk of phase noise, especially at the lower frequency range, wouldn't grounding and shielding play a very important role? I find lots of equipment have more low frequency noise than in the upper spectrum. Especially below 100Hz.
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Old 3rd May 2009, 08:14 PM   #106
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Quote:
Originally posted by CraigBuckingham



Those recording engineers are misguided.

Rubidium master clocks are optimised for good long-term stability as time references. Very short-term stability or phase noise that is in the low end of the audio band is therefore not as critical a design parameter.

Current state of the art crystal oscillators are virtually at the limits that physics dictates for the type or resonator used. SC cuts performing better than AT cuts.

Rubidium master clocks use a CRYSTAL OSCILLATOR stabilised to the rubidium hyperfine transition of 6 834 682 610.904 324 Hz. It is that hyperfine transition frequency accuracy that gives long-term accuracy by the use of synchronising to it.

The short-term accuracy is determined by the CRYSTAL OSCILLATOR used in the rubidium standard.

A brief description on that can be found here http://en.wikipedia.org/wiki/Rubidium_standard

A more detailed description here http://www.thinksrs.com/products/PRS10.htm

So to put it in simple terms the Rubidium standard oscillator is superfluous, redundant - lowers performance and adds unnecessary cost when applied to high quality audio/digital conversion.

Spot on, and thanks for this post, also from my Grimmaudio colleagues
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Old 4th May 2009, 03:45 AM   #107
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Quote:
Originally posted by Terry Demol



Misguided? They are merely reporting and acting on what they
hear. When a number of engineers report similar findings then it is
worth investigating what mechanisms are actually occuring.



I'm not so much interested in the absolute performance of
Rubidium, more the ADC's behaviour when being externally clocked
by one.

I suggest you go to:

http://www.grimmaudio.com/whitepapers.htm

Read whitepaper titled 'PLL and Clocking'. In particular point 7.

As shown in the graph, the only region an externally clocked ADC
can benefit is below the internal PLL's cutoff point, ie; low
frequencies. (Good paper Grimmaudio folks)

Others are getting benefits from ULN at LF PSU's on their oscillators,
so the finger points at one region - close in (to carrier) phase noise.

Dig?


T
You said,

This seems to be the case, there are plenty of recording engineers
throwing good hard earned cash at Rubidium master clocks.

As a generalisation, this frequency area is the only real possibility for
improvement when slaving an ADC off an external clock.

cheers

Terry



Terry,

1) Yes, they are misguided. Firstly by some manufacturers of Rubidium master clocks aimed at that market.
2) By people such as yourself suggesting they offer better close in noise performance.

You made the association about close in noise being asscociated with Rubidium master clocks.

In my reply to your post I countered with substantial references to why that was not the case.

What you are or are not interested in does not change the laws of physics. You need to understand that the physical world is not influenced by human emotion.

If you did not understand my post I suggest re-read it.

What is important is to understand why your assertions are not correct because of how a Rubidium master clock works. Then you will understand why a good oscillator is a better approach than a Rubidium master clock.

Try using google and do some research on the history and performance of crystal oscillators and you may have a better understanding on the subject matter.

Talk to experts, such as those ar NIST or Wenzel, SRS etc.

You may be able to then add some more usefull information to the subject thread.
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Old 4th May 2009, 07:10 AM   #108
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Default Re: Re: Re: Re: Re: Graphs

Quote:
Originally posted by QSerraTico_Tico
I find transparency, or the lack of it, not a strong point of your clock. So I wonder why you bring that up.
Simple. Transparency means "not changing the sound in any way". There are many ways of improving the apparent amount of microdetail in reproduction (usually to the detriment of microdynamics or tonal neutrality). I've often encountered boxes that, when you add them to a signal chain, increase apparent immediacy and detail markedly. Here's the crunch: at that point the signal at the output of the box has a lot more detail and atmosphere than the input does. This obviously means the output sounds clearly different from the input and that the box is therefore NOT transparent.

Ergo you can't just sit down and listen to a signal and declare that "transparent". You have to get hold of the same signal upstream in the signal chain and compare it A/B. Guido's clock was tested (against others) in this manner, by equipping AD and DA converters with a variety of clocks and comparing the AD input and the DA output. And yes: some clocks sounded like the DA output had much more going for it than the AD input, at least on some genres of music. But that is not what transparency is about.

It's fine if you prefer LC's clock. No problem. It just means you're into euphonics, not transparency. There is nothing wrong with euphonic, point is to know what you're after and then going after it directly.
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Old 4th May 2009, 07:24 AM   #109
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Default Re: Redbook vs. Good Sound

Quote:
Originally posted by Lars Clausen


However i think 100ppm deviation is in fact audible in an A/B test.
If the replay clock is a static 100ppm (0.01%) over the standard frequency, this corresponds to a 1.80m violinist playing a 50cm violin sounding like they are in fact 180um and 50um smaller, respectively. The 30m large concert hall in which he plays will sound 3mm smaller. Exceedingly plausible, I grant you.
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Old 11th May 2009, 07:57 PM   #110
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Very amusing analogy Guido, even though i'm having a hard time figuring out how the height of the musician affects the pitch of the music. Anyway i'm sure you have a good explanation for that :-)

How does jitter then fit into your classical musician formula? Rumbling in his stomache??
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