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1 hour ago, JohnSwenson said:

I'm NOT from Mutec, but I have a little bit of knowledge about crystal oscillators so I hopefully can offer some insight as to what aging is.

 

First off we need to understand that there is not just one aspect about crystal oscillators that have numbers, people here tend to like to latch onto numbers as figures of merit, but this can be fraught with danger since there are at least there different aspect of crystal oscillators that have numbers, before you start comparing numbers you ABSOLUTELY HAVE to understand which aspects those numbers refer to otherwise you are comparing surface tension to the color of the peel of an orange.

 

There are two primary aspects of a crystal oscillator:

 

1) phase noise (I have written exhaustively about this early in this thread so I will not duplicate it all here) This is not a single number, it is a graph.  This graph is the phase noise as an off set from the "carrier", which is the frequency of the signal coming from the oscillator. In a nutshell no oscillator produces a perfectly "pure" frequency. They all vary a little bit over time. Phase noise looks at the rapidly varying frequency changes. It is plotted in regards to frequency. If the output frequency varies a little higher, then a little lower, then a little higher and does this at a regular rate, this will show up as a spike in the graph (refered to as a "spur"). Real oscillators rarely do this, they kind of randomly fluctuate in frequency, such that this plot looks like a jagged continuous line. USUALLY much higher in value at the lower frequencies than the higher frequencies. From listener reports it seems that the lower offsets, (around 10Hz), seem to be the most import for audio. Unfortunately these are usually the most difficult to improve.

 

2) Actual frequency of the output. Due to above there is no such thing as AN actual frequency, it is wandering around. So the term "frequency of the output" is some form of averaging over time. That process can vary all over the place and is very rarely specified. Which of course makes comparing numbers rather difficult unless the same test equipment is used in exactly the same way. For example I have a frequency counter which has at least 30 different ways of measuring frequency, which will all give slightly different numbers.

 

#2 has several different subcategories:

 

#2.1) Accuracy. This is just the frequency out of the box. A high accuracy oscillator might be within 10 Hz of the number specified on the can and a lower accuracy one might be within 200Hz of the number on the can. Usually specified in Parts Per Million (PPM), thus a 1 PPM 10MHz oscillator can be up to 10Hz off the specified 10MHz. Some are so good they are specified in parts per billion (PPB). Unless it is pretty grossly off, this is pretty much unimportant for audio.

 

#2.2)  Temperature coefficient. All oscillators will change their frequency with a change in temperature, the Temperature coefficient (Tempco) specifies how much. It is usually measured in PPM per degree C. Unfortunately it is not a single number. Take an oscillator at 25C, raise the temp 1C and you will have a certain change in frequency, Start with the oscillator at 50C and change it one degree and you will get a VERY different  change in frequency. All crystal oscillators have some temperature where a small change in temperature makes almost no difference in frequency, if you are significantly away from this temperature the change can be VERY large for even a fairly small change in frequency.  Because this is measured in PPM/C a lot of people confuse it and accuracy since they both have PPM in the units but they are VERY different things, You can have high accuracy and lousy Tempco, or lousy accuracy and low Tempco. This has SOME affect on audio, but not a lot. The primary effect is at warm up, when a device is is turned on and the temperature inside the box is increasing. During this time the changing frequency can make a small audio difference. After reaching thermal equilibrium the Tempco has almost no effect on audio.

 

#2.3) Aging. This is the long term change in frequency over long time periods (measured in years). Most crystal oscillators have a fairly large change in frequency from year to year. During the first few years this is fairly large, then slowly goes down to almost no change after about say 15 years or so. Aging has essentially zero impact on audio.

 

#1 is the only one that has any significant impact on audio. Of the #2 categories Tempco is the only one which will have some impact on audo, but only during warmup. After the temperature settles down, almost no impact.

 

So in summary, spend money on low close in phase noise, money spent on high accuracy, low Tempco or low aging, is usually just throwing away your money. The OCXO is an exception to this, see below.

 

In particular a TCXO (temperature compensated crystal oscillator) is almost never a good thing for audio. A TCXO, has a normal crystal oscillator and a temperature sensor of some sort. The voltage from the temperature sensor is fed into a port on the crystal oscillator which causes its frequency to change with a varying voltage. This setup so it does some degree of cancellation of the crystal Tempco. So now we have a temperature sensor with almost always some degree of noise on the voltage output, feeding an input port which changes the frequency, thus rapidly varying the frequency, what is this called? Phase noise. Thus TCXOs ALWAYS have higher phase noise than a regular crystal oscillator using the same crystal and circuit minus the compensation. Yes it might have a smaller impact during warm up, but sound worse otherwise. Not usually a good use of money.

 

The type of crystal used in common crystal oscillators is what is called an AT cut. Its primary claim to fame is that the temperature where the zero Tempco appears ( sometime called the Tempco threshold or "knee" of the Temcp curve) happens near normal room temperature. This gives pretty good temperature behavior without doing anything else. But they do not have the best performance in other parameters. In particular for audio the phase noise of a different cut, called the SC cut, is much lower. BUT the knee in the Tempco curve is way up in the 90C range, at room temperature the Tempco is so bad that even a small temperature change drastically changes the frequency, so even for audio it is useless. This is where the OCXO comes in, the primary purpose is to raise the temperature of the SC cut crystal so it is sitting right at the knee of the Tempco. This gives an oscillator with a very low Tempco, very low aging and very low phase noise.

 

Not all OCXOs are created equal, in particular the less expensive OCXOs (say less than $100) do not use a crystal and circuit with particularly low phase noise, but they DO have very low Tempco and low aging, but the phase noise is no better than a $10 regular crystal oscillator. Again this is just a waste of money, you are spending money on something that doesn't make sound better. (note this is "new" price, not what you can get on ebay for a used one). BUT if you spend the money on a very special SC cut crystal and very special circuitry you can get the lowest phase noise of any oscillator known. It is not cheap, but this type of OCXO IS the way to get the lowest phase noise. OCXOs at this level also give you very low aging and very low Tempco, but these are not primarily the main reason for getting one of these OCXOs. Unfortunately for audio, most applications (other than audio) want very good specs for ALL the parameters, it should be possible for the manufacturers to optimize for phase noise only, thus giving us lower cost oscillators since they are not trying get say extremely low aging.

 

One other VERY important aspect about phase noise: comparing charts can ONLY be done if the frequencies are the same. The phase noise for an oscillator increacess by 6dBc/root Hz per octave of the oscillator frequency. Thus of you have plot for a 10 MHz oscillator and one for the same model oscillator at 20 MHz, the numbers will be 6 dBc/ root Hz higher. If you take that 20 MHz output and run it through a good flip flop, dividing the frequency by two, you will get the same phase noise plot as the 10MHz version.

 

So be VERY careful when comparing phase noise from different oscillators , they either need to be at the same frequency or you apply the 6 dBc/ root Hz rule. (explaining that rule is a little complicated so just take my word for it)

 

Sooo as far as aging is concerned, spec sheet aging has nothing to do with audio.

 

John S.

 

 

Thank you John. Another example of UpTone sharing their knowledge. A real example for the HiFi industry. Looking forward to the answer from Mutec as well.

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On 9/7/2018 at 7:46 PM, sam1000 said:

Congratulations and welcome back Julian!

 

I read somewhere on the forum that you are planning to sell an OEM cable to go with Ref10. What is the tentative timeline for the release.

 

It's something we're still looking into, but progress has been a little slow because we're currently focused on a much bigger, and (I think) more exciting project... 

I'll let you know as soon as there's news on the cable front though. 

 

Julian

MUTEC GmbH

Marketing Associate

Email [email protected]

Web www.mutec-net.com

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On 8/31/2018 at 7:32 AM, baconbrain said:

Certainly not an expert on this, but I believe the influence of external factors to the rate of deterioration must be a given. The question I would have back to you is: If the amount of benefit from the Ref10 is so subtle that one is concerned about a rate of deterioration +/-0.2 ppm (over 10 years), then is the total investment (Ref10 + cables + ....) warranted to begin with?

Thanks @julian.davidand @JohnSwenson.  Awesome answers.  It was just idle curiosity when I first raised the question of aging but glad the matter has now well and truly been put to bed.

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1 hour ago, julian.david said:

 

It's something we're still looking into, but progress has been a little slow because we're currently focused on a much bigger, and (I think) more exciting project... 

I'll let you know as soon as there's news on the cable front though. 

 

Julian

A bigger and more exciting project?  Interesting, I have to say that I have thought for a while that the REF10 looks a little lonely as the only product in Mutec's "Empyreal Class" category, is the REF10 going to get some Empyreal Class company?  For me, an Empyreal Class version of the MC3+USB would be most excellent.  I know that I am being slightly mischievous here, I am sure that if you could say more in the short term you would, and that when you are ready to say something, I am sure you will.  Meanwhile, it's fun to speculate.?

 

Anyway, many thanks for the feedback on the other points regarding aging etc., very much appreciated.  Thanks also to @JohnSwenson, great stuff as always.

Windows 11 PC, Roon, HQPlayer, Focus Fidelity convolutions, iFi Zen Stream, Paul Hynes SR4, Mutec REF10, Mutec MC3+USB, Devialet 1000Pro, KEF Blade.  Plus Pro-Ject Signature 12 TT for playing my 'legacy' vinyl collection. Desktop system; RME ADI-2 DAC fs, Meze Empyrean headphones.

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12 hours ago, JohnSwenson said:

it should be possible for the manufacturers to optimize for phase noise only, thus giving us lower cost oscillators since they are not trying get say extremely low aging.

 

 

Q

 

and look at the cut, not “OXCO” 

 

12 hours ago, JohnSwenson said:

 

One other VERY important aspect about phase noise: comparing charts can ONLY be done if the frequencies are the same. The phase noise for an oscillator increacess by 6dBc/root Hz per octave of the oscillator frequency. Thus of you have plot for a 10 MHz oscillator and one for the same model oscillator at 20 MHz, the numbers will be 6 dBc/ root Hz higher. If you take that 20 MHz output and run it through a good flip flop, dividing the frequency by two, you will get the same phase noise plot as the 10MHz version.

 

Excellent point! 

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23 hours ago, julian.david said:

 

It's something we're still looking into, but progress has been a little slow because we're currently focused on a much bigger, and (I think) more exciting project... 

I'll let you know as soon as there's news on the cable front though. 

 

Julian

 

I would be curious to know if the new project / product will be released in the near (next 90 days) or distant future?  ?

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Julian, 

 

If the Ref is used to reference any device or specifically a normal vcxo, how much does it contribute to the lower phase noise of the master?

 

So will a Ref 10 refencing a mc3+USB, it there any further improvement or benefit of having a  better or even lower phase noise osc in the mc3+ usb? 

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10 hours ago, baconbrain said:

 

I would be curious to know if the new project / product will be released in the near (next 90 days) or distant future?  ?

 

It's not going to be in the next 90 days and then we're hitting Christmas time, so let's say we're shooting for early 2019. But let me also say that any major roadblock could easily set us back. You guys here will definitely be among the first to learn about it.

MUTEC GmbH

Marketing Associate

Email [email protected]

Web www.mutec-net.com

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3 hours ago, justubes said:

Julian, 

 

If the Ref is used to reference any device or specifically a normal vcxo, how much does it contribute to the lower phase noise of the master?

 

So will a Ref 10 refencing a mc3+USB, it there any further improvement or benefit of having a  better or even lower phase noise osc in the mc3+ usb? 

 

Hi, 

I'm not quite sure I fully understand your question. If it is whether or not the REF 10 can improve the MC-3+USB then the answer is yes, absolutely. That's what the external re-clock mode in the MC-3+USB is for and one of the reasons we even made the REF 10. In fact, our trade show demo system has in the past consisted of an MC-3+USB playing back audio from Roon on a laptop to a headphone DAC. As part of the demo we would switch from re-clocking based on the internal clock of the MC-3+USB to the external clock reference from the REF 10. The effects could be quite easily discerned by booth visitors despite the pretty noisy show floor. 

 

Does that answer your question or did I somehow misinterpret it?

 

Julian

MUTEC GmbH

Marketing Associate

Email [email protected]

Web www.mutec-net.com

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@julian.david I think the question is this ... if you're using a REF10 into an MC-3+ USB, would there be any benefit to having a better (lower phase noise) clock in the MC-3+ USB than the one in the current product?  I guess the speculation is that an Empyreal class version of the MC-3+ USB might have a better clock than the current product.

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Yes I understand in a product implementation that will increase the cost and make lines finer between theproduct lines. 

 

Just for further understanding and discussion. 

 

Suppose the base of the mc3+usb has a even lower phase noise clocking, closer to that of the Ref 10, this would surely increase the cost a fair bit to also get a better power supply into a larger unit. The question is even if still fed by the Ref 10 Which still has a better phase noise. How much does this external reference contribute to the overall phase noise in comparison to the mc3+ usb now as it is vs. Fitted with an even better oscillator. 

 

Is the determining factor more so the internal oscillator in the mc3+usb or will the better external reference still be the dominant and determining factor of the low phase noise in the mc3+ usb? 

 

If we rate. In a scale of 100% and take the base of the Ref 10 as 100 for low phase noise in clocking  scoring

 

Ref 10= 100 (base, best clock>

Mc3+USB = 80

MC3+ USB plus ref 10 =90

MC3+ with improved oscillator over current 10g clocking plus the Ref 10 =?? 

 

Will there be yet another nice jump to say a score of 95 or will the score still be similar to 90, since the Ref 10 is disciplining the MC3+usb? 

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  • 4 weeks later...

I made a point in reference to REF10 (pan not intended) in a different thread, comparing it to the upgraded Cybershaft, and Julian suggested I move it here.  Here's his reply:

 

Hi there, 

While it’s true that some of Cybershaft’s latest 10 MHz clocks match the phase noise performance of the REF 10 at 1 Hz offset at a lower price, I think it’s also worth pointing out that these OCXOs are used, recycled oscillators with potentially questionable long-term performance. This is no secret as Cybershaft themselves note it in the fine print of these product pages. We’ve been doing quite a bit of research in this field at MUTEC prior to the launch of the REF 10. Our main developer has inside knowledge of the second-hand oscillator market and how these oscillators are handled in the process. So for us at MUTEC there were and still are a lot of reasons why we stay away from these predominantly Chinese-sourced recycled OCXOs.  

 

Sure, there’s a 2-year warranty but a performance decay and functional unreliability may easily slip in unnoticed over time. Buying a REF 10 guarantees a brand-new, carefully tested German-made OCXO that will provide excellent performance for many years to come. I personally believe there’s a real value in having the peace of mind that your newly bought equipment performs at its peak. But ultimately the great thing about competition is that everybody can make those decision on their own depending on their preference and budget.

 

BTW, this discussion is probably better suited to take place in the REF 10 thread but I still thought it'd be worth chiming in here.

 

Hope this helps,

Julian

Stereo

[Genelec 1032C x 2 + 7360 x 2] <== [MC3+USB x 3 <-- REF10 SE120] <== [AERIS G2] <== [EtherRegen x 3]
Chain switchable to [Genelec 8331 x 2 + 7350]


Surround

[Genelec 1032C x 3 + 8431 x 2  + 7360 x 2] <== [MiniDSP U-DIO8] <== [Mac Mini] 

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You make very compelling points, Julian. Thank you.

 

 Since I’m in the market, I’d like to ask a few public questions that might be to the benefit on others:

 

  1. Your literature mentions the square signal and steel chassis as contributing factors to the REF10 performance. How influential are they? Crudely speaking, 5%, 10%? 
  2. How many years for continuous use can one expect from the REF10? Roughly of course.
  3. Is there a point in time in which a re-calibration is in order? Is that a service Mutec offers?
  4. How far apart can I place the REF10 from the slave? I have 2 systems that could benefit from the REF10. One would demand a 14-meter word clock cable, though…

 

Thanks in advance!

Stereo

[Genelec 1032C x 2 + 7360 x 2] <== [MC3+USB x 3 <-- REF10 SE120] <== [AERIS G2] <== [EtherRegen x 3]
Chain switchable to [Genelec 8331 x 2 + 7350]


Surround

[Genelec 1032C x 3 + 8431 x 2  + 7360 x 2] <== [MiniDSP U-DIO8] <== [Mac Mini] 

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