Cybershaft rubidium clock...low priced option?

[tboooe]

There is a discussion on Audiogon about a clock being made by Cybershaft in Japan that is supposed to be very good while also being resoanably priced at around $1500.

 

Here us the thread over at Audiogon, check out the post starting on 3-25-16 by zephyr24069.

https://forum.audiogon.com/discussions/rubidium-clock

 

Just curious if anyone has heard of this company? I may pull the trigger and try it with my Mutec 3+ USB converter. It would be interesting to see if it spoinds better than its internal clock.

 

Here is the webpage for Cybershaf

http://thttp://www.cybershaft.jp/

[Nikhil]

Correction: Cybershaft Website

 

http://www.cybershaft.jp/

[planner]

I have been using the Sfrozato PCM-02 EX with MC-3 + with great results. Just another option for you to consider.

 

http://en.sfz.co.jp/products/pmc/

[tboooe]

I have been using the Sfrozato PCM-02 EX with MC-3 + with great results. Just another option for you to consider.

 

http://en.sfz.co.jp/products/pmc/

 

Do you mind if I ask how much that unit cost? Also, do you know what the clock output impedance is with the Sfrozato? The Mutec needs 75ohm correct? The Cybershaft one is 50ohm though I am not too sure how much of a difference it makes.

[planner]

It's about $2,500. Output impedance is 50 ohm. But I have been using a Oyaide 75 ohm digital cable without issues. I didn't deactivate the 75 ohm termination on the Mutec as well. Quite difficult to find a high quality 50 ohm cable these days, so I just leave it as it is.

[tboooe]

It's about $2,500. Output impedance is 50 ohm. But I have been using a Oyaide 75 ohm digital cable without issues. I didn't deactivate the 75 ohm termination on the Mutec as well. Quite difficult to find a high quality 50 ohm cable these days, so I just leave it as it is.

Ok thank you. Thats a quite a bit more than the ones offered by Cybershaft. I wonder what the difference is (besides the usual audiophile markup)? Admittingly I do not know much about clocks. BTW, it looks like Cybershaft offers a GPS enabled clock. How is this better than a clock without GPS locking? Is GPS locking more accurate somehow? My concern is that not being able to get a GPS lock.

[barrows]

hahahaha, am I the only one who finds the name cyberSHAFT kind of telling, especially when they are producing a Rubidium XO?

[alan_un]

It's about $2,500. Output impedance is 50 ohm. But I have been using a Oyaide 75 ohm digital cable without issues. I didn't deactivate the 75 ohm termination on the Mutec as well. Quite difficult to find a high quality 50 ohm cable these days, so I just leave it as it is.

 

The question if the clock can be connected to a 75Ω equipment was answered on their website (Google Translation):

 

"The output impedance of this unit is 50Ω, but it also can be connected without any problems to 75Ω of equipment. Output level Please check the voltage value that has been described in the "product offerings and specifications" column of the above because slightly different at the time of 50Ω at the time and 75Ω. In addition, when connected to 75Ω get up things that somewhat reflected wave from an impedance mismatch there was no effect of appreciably in the Allan variance and phase noise value is our test. Cable length to connect the clock is considered to influence if there is no longer such as more than 5m is negligible."

[tboooe]

The question if the clock can be connected to a 75Ω equipment was answered on their website (Google Translation):

 

Thank you...I saw that too but was wondering if the explanation is correct and if there is any degradation to the input clock signal.

[alan_un]

Thank you...I saw that too but was wondering if the explanation is correct and if there is any degradation to the input clock signal.

 

I am quite lucky as they have listed the equipment I am intending to connect in their list of compatible audio products. In general, though, I think they are quite correct with their statement. If the input voltage can be accepted by your equipment, you should be OK. I do not think that there is any degradation of the signal, provided your connection is not too long.

[Elberoth]

My friend just bought the $1000 CyberShaft Premium OCXO:

 

CyberShaft OCXO Premium

 

It already has much lower jitter than the $23.000 Esoteric G-01 Rubidium Clock, not to mention the $6000 Antelope crap:

 

 

He will test it with his dCS Vivaldi stack (directly connected to the 10M clock input on the Vivaldi clock).

 

If it performes as expected, we will try the $2800 Cybershaft OCXO Limited IP17 clock:

 

[tboooe]

My friend just bought the $1000 CyberShaft Premium OCXO:

 

 

Thank you! Looking forward to your impressions.

[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?

[tboooe]

BTW, instead of the OCXO Limited, would the "double clock mounted" be a good step up from the Premium?

 

ƒ_ƒuƒ‹ƒNƒƒbƒN“‹Ú

 

[gldgate]

BTW, instead of the OCXO Limited, would the "double clock mounted" be a good step up from the Premium?

 

ƒ_ƒuƒ‹ƒNƒƒbƒN“‹Ú

 

 

It's two separate clocks. You get the OCXO Premium and Rubidum in one chassis. The one person I know who has this unit greatly prefers the OCXO Premium over the Rubidium and uses it the vast majority of the time.

[Elberoth]

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?

 

1. I did jitter calculations myself. Jitter is calculated from the phase noise. It is a simple math.

 

You have to enter the Carrier Frequency in MHz, Integration Bandwidth (1 to 100Hz) and Offset & Amplitude data (Freq and phase noise figures).

 

I have used this jitter calculator:

 

Abracon Phase Noise/Jitter Calculator

 

2. The dCS Vivaldi clock has a suitable 'master clock' 10MHz input.

[Elberoth]

BTW, instead of the OCXO Limited, would the "double clock mounted" be a good step up from the Premium?

 

ƒ_ƒuƒ‹ƒNƒƒbƒN“‹Ú

 

 

Looking at the numbers, which I have seen somewhere, it would ba a major downgrade. The Cybershaft Limited uses Rakon HSO-14 clock (which is basicly Oscilloquartz BVA-8607 XO) which I believe is the lowest plase noise clock available on the market - far exeeding any Rubidium clock I've seen.

[JohnSwenson]

BTW, instead of the OCXO Limited, would the "double clock mounted" be a good step up from the Premium?

 

ƒ_ƒuƒ‹ƒNƒƒbƒN“‹Ú

 

 

A rubidium standard offers NO advantage over the very good OCXO. The rubidium standard has two systems, a rubidium oscillator, which has high jitter but very good long term stability and an OCXO with very low jitter but not as good long term stability. Some complex circuitry in side there reads both and every so often slowly tweaks the OCXO to match the long term averaged frequency of the rubidium oscillator.

 

Because the OCXO is an adjustable oscillator it actually has slightly higher jitter than the fixed OCXO. Audio could care less about absolute frequency accuracy over tens of years time frame so the rubidium version has higher jitter and costs more, not particularly a good combination for audio use. (unless it is all about bragging rights, but that is something else!)

 

The phase noise specs for those cybershaft OCXOs are actually very good for the price. The big issue with any such external frequency reference is how it gets into the DAC and what happens to it in there.

 

First off, many frequency standards are sine wave output, a lot of DACs that have external inputs want a square wave not a sine wave. Make SURE the reference and the DAC will work together before spending any money.

 

Almost no DAC or audio device uses 10MHz directly. In order to use it the frequency has to be converted. What that conversion does to the phase noise of the input can vary wildly. The absolute best systems out there are at about on par with the phase noise from the premium. So with a premium you would be getting about twice the jitter inside the DAC. With the limited the internal jitter is going to be several times higher than the reference, hence there is not going to be much of an actual difference in the DAC, for a much bigger cost.

 

The above assumes your DAC has a state of the art frequency conversion circuit, these are pretty rare and expensive but COULD exist in one or two audio devices. The problem is that any device with such a conversion circuit probably already has a REALLY good local oscillator, so using one of these OCXOs going through the conversion is not necessarily going to give you lower jitter in the DAC. It may, but it may not.

 

John 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.

[Astralark]

Why I could not see that post？

 

 

Sent from my iPhone using Computer Audiophile

[Elberoth]

Keith_W - there is a nice diagram that shows what JohnSwenson have explained (borrowed from pinknoisemag.com):

 

 

So as you can see, there is a regular XO inside the Rubidium Oscillators plus a Rubidium cell, photo detector and lots of electronics - all of which is useless for audio.

 

If you take that XO out of the Rubidium Oscillator, it would perform much better with regard to phase noise figures. Which is why regular XO have better phase noise figures.

 

So called 'Atomic clocks' for audio is nothing more than marketing. They use the Rubidium oscillators for bragging rights only. It doesn't mean some of them aren't good and can't make your system sound better. Clocks like Esoteric G-01 ore very good and many Esoteric and dCS users reported excellent results with using those. The problem is, that for far less money, you can get even better performing OCXO !

 

The rubidium oscillator used by Esoteric - Stanford Research Systems PRS-10 - costs $1300 in OEM. That is the cost of the Rubidium Oscillator itself. The very same company - Stanford Research Systems - makes OCXO that far exceeds their PRS-10 rubidium module on phase noise performance, for 1/3 of the price.

 

If Esoteric decided to switch from the SRS Rubidium oscillator to SRS OCXO, they would instantly make their clock sound better. But they won't, as all the bragging rights would be gone, too !

 

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

[Elberoth]

First off, many frequency standards are sine wave output, a lot of DACs that have external inputs want a square wave not a sine wave. Make SURE the reference and the DAC will work together before spending any money.

 

That is a very good remark.

 

All Esoteric DACs and CDPs accept 50 Ohm, 10MHz sine wave:

 

ESOTERIC/Dual Mono D/A Converter D-02 | ESOTERIC COMPANY

 

On the other hand, the affordable TEAC UD-503 requires 50 Ohm, 10MHz rectangle wave:

 

http://www.teac.com/content/downloads/products/935/ud-503_om_efs_va.pdf

[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.

[One and a half]

One thing that puzzles me a little about the Clock in the Cybershaft. Clocks are not cheap, and unless you buy them in the thousands, the minimum asking price by Rakon is several thousand EUR. I don't understand how the Cybershaft can sell their device at less than 2k, when the clock alone is over their MSRP.

Are they seconds or something? Would it be possible to see a photo inside showing the Rakon clock?

 

On another issue, the implementation of an external word clock to a DAC, needs to be built in from the word go. In a typical PLL (PID) the external clock needs to be very accurate and cabling to the DAC critical, since any compensation schemes would just add to jitter. After all, the control loop is going out of the box, so goodness knows what protection systems there are to avoid several volts on a small circuit inside the DAC.

 

I would say in Esoteric's case, the internal clocks are not the greatest and rely on external clocks to make their players/dacs sound better As for the 50 Ohm /75 Ohm impedance mismatch, at these frequencies, the impedance needs to match surely, I would not expect a wide variation to come good.

 

As always, it's the implementation that counts.

[Elberoth]

The best engineering practice is to use the very best local XO, as close as possible to the DAC chip itself. If you have to use a separate transport, you can always send the clock signal back from the DAC to the transport.

 

The dCS and Esoteric's (who followed dCS steps) soultion is flawed. Sending clock from an extrernal box, via extra cables and PLLs, always degrades the clock signal quality. I belive dCS had chosen this solution since they started as a proaudio company, and that is how things are done in the recording studios. In a studio reality, you have to synchronise multiple digital devices (not just the CD transport), hence the need for an extrenal 'house clock'.

 

So even though the concept of an external clock is flawed, but it doesn't mean, you can not improve it in the systems that rely on it.

 

To give you a car example: I think we can all agree, that an independent suspension is a better solution for a sports car, than a live axle. But it doesn't mean, that you cannot improve the handling of the older Mustangs that have live axles.

 

Same here. The solution with an external clock is not ideal, but under certain conditions (very high quality clock), you can still improve systems that use one. And this is what dCS and Esoteric owners report hearing, after adding the external clock.