Superclocks

[plissken]

Here is a way to effectively evaluate these clocks by ear and would best with a get together most likely:

 

Get a pre-amp like the Emotiva XPS-1 that has balanced (xlr) inputs. Setup a computer and drive the same DAC's simultaneously with the only difference being a modded clock. Queue up your material and then switch between inputs. Have someone do some random swaps and see if you can follow the yellow bouncing ball without knowing which is which.

 

You can also use this to evaluate USB cables and 2 port USB hubs. 

[Hammer]

9 hours ago, plissken said:

Here is a way to effectively evaluate these clocks by ear and would best with a get together most likely:

 

Get a pre-amp like the Emotiva XPS-1 that has balanced (xlr) inputs. Setup a computer and drive the same DAC's simultaneously with the only difference being a modded clock. Queue up your material and then switch between inputs. Have someone do some random swaps and see if you can follow the yellow bouncing ball without knowing which is which.

 

You can also use this to evaluate USB cables and 2 port USB hubs. 

Are these clocks different than a rubidium clock from say Stanford Reseach Systems?  I picked one up on the cheap off eBay and had been meaning to purchase a DAC such as a Mytek which accepts clock input to play around, but have not had the time.  Has anyone tried this with good result?  Thanks, hammer

[JohnSwenson]

On 4/25/2017 at 4:11 PM, Hammer said:

Are these clocks different than a rubidium clock from say Stanford Reseach Systems?  I picked one up on the cheap off eBay and had been meaning to purchase a DAC such as a Mytek which accepts clock input to play around, but have not had the time.  Has anyone tried this with good result?  Thanks, hammer

Rubidium clocks are usually very bad to use for audio. They have very good long term stability, but high phase noise. The long term stability has nothing to do with audio but the close in phase noise is what is important. So a rubidium is exactly the wrong oscillator to use.

 

Another problem is that the rubidium is probably NOT going to be outputting a frequency that can be used directly by audio circuitry, so some for of frequency synthesizer is going to have to be used, and these ALWAYS increase the phase noise.

 

A rubidium is great for an actual clock (you can read the time) that you want to be accurate to the microsecond over years of run time, but not so good for audio.

 

John S.

[hurka]

[STC]

On 4/25/2017 at 9:33 PM, plissken said:

Queue up your material and then switch between inputs. Have someone do some random swaps and see if you can follow the yellow bouncing ball without knowing which is which.

 

Another blind test to prove otherwise?

 

I am running 18 zones simultaneously in sync using 4 different kind of DACs. Some of them cost $8.99 only. Of course, I downsample all my files to 44.1kHz. Not sure I am hearing any phase noise or even timing errors except at the beginning before JRiver syncs them. I must be missing something.

[monteverdi]

1 hour ago, JohnSwenson said:

Rubidium clocks are usually very bad to use for audio. They have very good long term stability, but high phase noise. The long term stability has nothing to do with audio but the close in phase noise is what is important. So a rubidium is exactly the wrong oscillator to use.

 

Another problem is that the rubidium is probably NOT going to be outputting a frequency that can be used directly by audio circuitry, so some for of frequency synthesizer is going to have to be used, and these ALWAYS increase the phase noise.

 

A rubidium is great for an actual clock (you can read the time) that you want to be accurate to the microsecond over years of run time, but not so good for audio.

 

John S.

Thats quite interesting statement considering how much Antelope Audio charged for their external clocks

[plissken]

48 minutes ago, STC said:

 

Another blind test to prove otherwise?

 

I am running 18 zones simultaneously in sync using 4 different kind of DACs. Some of them cost $8.99 only. Of course, I downsample all my files to 44.1kHz. Not sure I am hearing any phase noise or even timing errors except at the beginning before JRiver syncs them. I must be missing something.

 

Just a way to evaluate with the confidence that self delusion isn't going to creep in. 

 

[jabbr]

http://m.pnas.org/content/114/12/E2303.full

 

when those quantum clocks get entangled with quantum cables ... oh boy!

[Confused]

An open question.  A while ago I was fortunate enough to listen to the dCS Vivaldi Upsampler with and without the Vivaldi master clock.  To my ears it did sound better with the master clock.  In the UK the Vivaldi master clock retails for a cool £10,000.  Looking at the Vivaldi clock specs, I cannot see anything that looks superior to the Clock in a Mutec MC3+USB.  Am I missing something or the Vivaldi clock simply very expensive for what it is?  

[JohnSwenson]

23 hours ago, monteverdi said:

Thats quite interesting statement considering how much Antelope Audio charged for their external clocks

External clocks are useful in studio environments where you have to have say 32 channels and you are using 2 channel or 4 channel boxes, in order for things to work right you HAVE to feed the same clock into all the boxes.

 

But for a two channel system in a home setting where you do not need to synchronize multiple boxes an external clock is not needed. If a particular DAC sounds better with an external clock, that means the internal clock in that DAC is not that good.

 

This did happen (on purpose) with some professional equipment designed specifically for studio use. The designers assumed the equipment was going to be used in a studio with a master clock fed to multiple boxes, so they deliberately did not spend much money on the internal clock, assuming it would never be used.

 

For home use where you are not using multiple boxes together it is by far best to spend the money putting the clock inside the DAC box, you can get far better performance than spending the money on an external clocked system.

 

On rubidium clocks, there is a technique called "disciplinig" that uses a rubidium clock and an OCXO together. The OCXO frequency is very slowly changed (time period days or weeks) by comparison with the rubidium clock. This gives the best of both worlds, but is just wasted money for audio purposes, you get just as good results on sound quality by using the OCXO without the rubidium, for a lot less money.

 

BTW there is a program designed to analyze disciplined clock systems called Lady Heather, I leave it to the reader to figure out why.

 

John S.

[Confused]

I must admit I remain puzzled about clocks through the audio chain.  Obviously multiple clocks are needed when processing data in a PC and transferring via a network for purely functional reasons, but why is super clock accuracy and jitter important in anything other than the last clock in the DAC.  You could argue that as long as all the bits are there, buffered, and in the right order, then clocking accuracy and jitter do not really matter, the clock in the DAC will sort out the timing and all will be perfect.  The reality is that folk worry about clocks in computers, network end points, USB add on devices, jitter from hard drives, computer processes and so on, but you could form a logical argument that none of this matters.  To be clear, I am not trying to argue that this is indeed the case.  From my own experience optimisation of this type in the PC and the audio chain prior to the DAC can make a huge difference to the end result.  It's just that logically I find it difficult to rationalise why this should be the case.  As an example, pull an Ethernet cable out of a network switch in my set up, the music keeps playing for a second or so, so how can anything upstream of that cable be making any difference whatsoever?  And yet, my experience shows that the upstream stuff genuinely does matter, it is just that the explanations I have seen for this in the past just don't seam to always hang together logically.  Sometimes I wonder how I sleep at night!

 

[Elberoth]

On 22.04.2017 at 10:48 PM, Superdad said:

 

Reasonable points and questions: Yes, the oscillator manufacturers are measuring their clocks--and the performance of those is of course not at all the same as the jitter performance of a complete DAC.

 

I will tell one interesting story:

Crystek has gotten a LOT better making their XOs!  18 months ago John and I requested and received samples of their CCHD-575 (the one Jonathan linked to above).  Got 25.0MHz version (for testing in the ISO REGEN).  They sent us 3 samples, and they each came with individual phase-noise plots.

Whereas the data sheet on Crytek's web page shows -100dB for 10Hz offset (in the mid-20MHz f-range we are using), the plots for the 3 samples we got were -108dB, -110dB, and -112dB at 10Hz!   

Of course our first thought was that they hand-selected these and that production runs could not be anywhere near as good as these.  So I immediately picked up the phone and called Crystek (they are actually not that large a company; one sales engineer seems to handle the whole country).  They said no, the samples were not at all specially selected--just measured right off the line. And he said that their processes have improved so much that the $9.60 CCHD-575 (that's what I paid for the first 500 pieces; goes to $9.30 ea. @ 1,000) now outperforms their big $27 CCHD-957 as used in a lot of top-tier DACs.   I told him they ought to update the 575's datasheet on the web to reflect that.  Guess he did not relay that suggestion to their marketing department. 

 

Of course if you want to see eye-popping phase-noise performance, then check out the Pulsar Clock. -118dB to -123dB at 10Hz!  But it is 420 Euros...

 

What makes you think that the processes improvments he is talking about did not result in better real world numbers for the CCHD-957 as well ?

[Elberoth]

On 27.04.2017 at 3:20 AM, JohnSwenson said:

Rubidium clocks are usually very bad to use for audio. They have very good long term stability, but high phase noise. The long term stability has nothing to do with audio but the close in phase noise is what is important. So a rubidium is exactly the wrong oscillator to use.

 

Another problem is that the rubidium is probably NOT going to be outputting a frequency that can be used directly by audio circuitry, so some for of frequency synthesizer is going to have to be used, and these ALWAYS increase the phase noise.

 

A rubidium is great for an actual clock (you can read the time) that you want to be accurate to the microsecond over years of run time, but not so good for audio.

 

John S.

+1

 

I recommend everyone here to read this 2 pages long essey on clocking:

 

http://www.grimmaudio.com/site/assets/files/1088/picoseconds_or_ppm.pdf

 

It is very easy to read for non techies like us and explains why crystals are better than Rubidium Clocks for audio and why long term stability (in ppm) does not metter one bit.

[ElviaCaprice]

Well, from a technical perspective, we don't know what all the clocking can do for streaming audio?  From a listening perspective, I trust Romaz's ears and he finds it's making a big difference in SQ, at least with the sotm new clocks.  I'm sure the Chord DAVE has excellent clocks, so how that relates to external clocking of the USB stream and it's relation???  But it seems to make a big difference and that is all that matters to me. 

[davide256]

Go here for why Chord DAC's are successful... its not directly related to clock

 

http://www.the-ear.net/how-to/rob-watts-chord-mojo-tech

[ElviaCaprice]

45 minutes ago, davide256 said:

Go here for why Chord DAC's are successful... its not directly related to clock

 

http://www.the-ear.net/how-to/rob-watts-chord-mojo-tech

Sorry, I fail to see the relevance to the subject on hand.  This article fails to even mention the DAVE's clocking.  The real question is why does, what appears to be, great additional clocking outside the DAC make a big difference in SQ with the DAVE?

[greenleo]

1 hour ago, davide256 said:

Go here for why Chord DAC's are successful... its not directly related to clock

 

http://www.the-ear.net/how-to/rob-watts-chord-mojo-tech

Do mean whether a clock is good or not does not matter?

[mmerrill99]

54 minutes ago, ElviaCaprice said:

Sorry, I fail to see the relevance to the subject on hand.  This article fails to even mention the DAVE's clocking.  The real question is why does, what appears to be, great additional clocking outside the DAC make a big difference in SQ with the DAVE?

Well Uptone/Swenson's reasoning for better clocks (& therefore better signal integrity, lower jitter) was that it required less overhead at the chip receiving & processing the signal. The logic was that this reduction in overhead generated less internal noise on the ground plane of the chip & ultimately on the ground plane of the power distribution system to which the sensitive DAC chips are connected & effected by such small noise fluctuations.

 

Unfortunately, it appears that these noise fluctuations are very low in amplitude & difficult to measure.

 

Now how a clock on a purely digital upstream device can audibly affect the DAC requires a deeper system analysis  

[STC]

57 minutes ago, mmerrill99 said:

Now how a clock on a purely digital upstream device can audibly affect the DAC requires a deeper system analysis 

 

It is possible that clock can affect the SQ. This article answers all those questions raise here

 

http://www.soundonsound.com/techniques/does-your-studio-need-digital-master-clock

 

Conclusions

Overall, it should be clear from these tests that employing an external master clock cannot and will not improve the sound quality of a digital audio system. It might change it, and subjectively that change might be preferred, but it won't change things for the better in any technical sense. A‑D conversion performance will not improve: the best that can be hoped for is that the A‑D conversion won't become significantly degraded. In most cases, the technical performance will actually become worse, albeit only marginally so.

[mmerrill99]

1 hour ago, STC said:

 

It is possible that clock can affect the SQ. This article answers all those questions raise here

 

http://www.soundonsound.com/techniques/does-your-studio-need-digital-master-clock

 

Conclusions

Overall, it should be clear from these tests that employing an external master clock cannot and will not improve the sound quality of a digital audio system. It might change it, and subjectively that change might be preferred, but it won't change things for the better in any technical sense. A‑D conversion performance will not improve: the best that can be hoped for is that the A‑D conversion won't become significantly degraded. In most cases, the technical performance will actually become worse, albeit only marginally so.

Pretty dubious conclusions based on limited tests - way over generalised from the specific.

 

I wouldn't for a minute claim that  "This article answers all those questions raise here"

[davide256]

3 hours ago, mmerrill99 said:

Pretty dubious conclusions based on limited tests - way over generalised from the specific.

 

I wouldn't for a minute claim that  "This article answers all those questions raise here"

you would need to see source and destination using the same higher clock as carrier frequency to gain a significant benefit

[greenleo]

On 2017/4/28 at 2:20 PM, Confused said:

I must admit I remain puzzled about clocks through the audio chain.  Obviously multiple clocks are needed when processing data in a PC and transferring via a network for purely functional reasons, but why is super clock accuracy and jitter important in anything other than the last clock in the DAC.  You could argue that as long as all the bits are there, buffered, and in the right order, then clocking accuracy and jitter do not really matter, the clock in the DAC will sort out the timing and all will be perfect.  The reality is that folk worry about clocks in computers, network end points, USB add on devices, jitter from hard drives, computer processes and so on, but you could form a logical argument that none of this matters.  To be clear, I am not trying to argue that this is indeed the case.  From my own experience optimisation of this type in the PC and the audio chain prior to the DAC can make a huge difference to the end result.  It's just that logically I find it difficult to rationalise why this should be the case.  As an example, pull an Ethernet cable out of a network switch in my set up, the music keeps playing for a second or so, so how can anything upstream of that cable be making any difference whatsoever?  And yet, my experience shows that the upstream stuff genuinely does matter, it is just that the explanations I have seen for this in the past just don't seam to always hang together logically.  Sometimes I wonder how I sleep at night!

 

In my point of view, a DAC is an analogue device.  Different analogue signals may give the same digital value after quantization but still different analogue signals.  Hence different clocks give different analogue signals and the DAC outputs different sound.

 

 

[STC]

21 minutes ago, greenleo said:

In my point of view, a DAC is an analogue device.  Different analogue signals may give the same digital value after quantization but still different analogue signals.  Hence different clocks give different analogue signals and the DAC outputs different sound.

 

 

 

Dfference also can be due to different sensitivity and impedance of the DACs. There seemed to be no standard number in Audiophile's DAC. 

[4est]

On 4/28/2017 at 10:31 AM, STC said:

 

It is possible that clock can affect the SQ. This article answers all those questions raise here

 

http://www.soundonsound.com/techniques/does-your-studio-need-digital-master-clock

 

Conclusions

Overall, it should be clear from these tests that employing an external master clock cannot and will not improve the sound quality of a digital audio system. It might change it, and subjectively that change might be preferred, but it won't change things for the better in any technical sense. A‑D conversion performance will not improve: the best that can be hoped for is that the A‑D conversion won't become significantly degraded. In most cases, the technical performance will actually become worse, albeit only marginally so.

 

I fail to see the reverence here. This article is talking about master clocks which is an age old argument ala cables or vinyl. The SOtM USB Ultra is USB regenerator and it is a different clocking system altogether than that of a master clock -even though SOtM makes master clocks as well.

[Johnseye]

On 4/28/2017 at 6:45 AM, davide256 said:

Go here for why Chord DAC's are successful... its not directly related to clock

 

http://www.the-ear.net/how-to/rob-watts-chord-mojo-tech

 

Good read.  Taps.  I had no idea.  You learn something new every day.