Cybershaft rubidium clock...low priced option?

[Keith_W]

Thank you. I have a couple of questions:

 

1. Is the jitter performance claimed, or measured?

2. The clock output is 10MHz. Some DAC's which allow external clock output need to be fed clocks at a base sample rate - e.g. 44.1, 48, 192kHz, etc. How do you convert the sample rate to match these DAC's?

[Keith_W]

Thank you John, for an extremely valuable post. I was considering getting a Rubidium clock, but don't think I will any more. I was somewhat surprised to see Elberoth's post showing much lower jitter on that OCXO compared to the Antelope 10M rubidium clock, and was wondering how on Earth could this be. Your post explains it all. You have saved me several thousand dollars.

[Keith_W]

For those interested to read more why atomic clocks are not suitable for audio, there are two very informative articles (written for non techies) that I highly recommend:

 

Grimm Audio on Atomic Clocks

The Future of Clocks: Clarifications in the Audio Clocking Paradigm

 

Thank you once again. It took me a couple of hours between chores to read both articles.

 

Now that I have read them, I should say: yes, I highly recommend them too.

 

What I got most out of that article is that they said that whether an external clock works on your DAC is mostly a crap shoot and depends on the design of the PLL on your DAC, and the difference between fast and slow PLL's. Given that manufacturers usually do not publish this data, and the article states that most PLL's are of the slow type (meaning more sensitive to its internal clock) - it really is a crap shoot whether an external clocking device will work for you or not.

 

The manufacturer of my DAC (Merging+ NADAC) only has this to say about use of an external clock:

 

"The MERGING+NADAC is fitted with a high quality internal clock. The quality of this is shown by the excellent laboratory measurements that the MERGING+NADAC produces. A word clock input on the rear panel allows the use of an external precision clock, which may in some cases be desired, or required by the overall system setup. The quality of external clocking devices varies, so before committing to a purchase, it should be tried with the MERGING+NADAC first."

 

... and their install instructions for an external clock (here) is painfully short on detail. It does not even say that it requires a sine wave or a square wave. All I know is that I need to be able to change the base frequency and can not use a 10MHz clock.

 

Given that they are a respected manufacturer of pro audio equipment, one would assume they are using a decent clock. But then again, so was Digidesign.

 

As for their suggestion that you should try a clock with their product before committing to purchase - that is nigh on impossible in the real world.

[Keith_W]

Antelope on the other hand, looks like a complete garbage.

 

Sure looks like it. But unless I am mistaken, Antelope is the only company that synthesizes 44.1, 48, etc from the 10MHz base clock? Some of us (like me!) can't use 10MHz base clocks.

[Keith_W]

Wow! Those are amazing specs on the Sforzato; I may have to check that out but that price point may be off the charts for a clock (for me)! The aluminum block construction and how they channeled out the interior cavities is amazing. That is one serious piece of engineering!

 

Yes, but unfortunately it has 10MHz sine wave output. For me, I would need a synthesizer to generate a 44.1 or 48kHz sine wave.

[Keith_W]

I don't know much about external clocks, but I got interested as I have a Brooklyn DAC that has a wordclock in and out. So how do we know if this clock is compatible with the Brooklyn or with any other DAC?

 

You find out by reading this: https://mytekdigital.com/download_library/manuals/Brooklyn_DAC_Manual.pdf

 

Seems as if your Brooklyn needs a digital input between 44.1kHz and 192kHz. This means you need a clock that can output these frequencies. Any clock that outputs a lab grade frequency (10MHz) is not suitable, unless you feed that output into a clock synthesizer, like this one: OCX HD 768 kHz HD Master Clock | Antelope Audio