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austinpop

A novel way to massively improve the SQ of computer audio streaming

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34 minutes ago, austinpop said:

I gather Alex has blessed this enterprise, and an order has been suitably placed in the system.

Alex replied within 15 minutes and the order was placed.  I'm looking forward to your test reports.

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1 minute ago, limniscate said:

@austinpop

 

Does this mean I'll get to hear the ISO-Regen in my system as well?

 

I'm counting on it! That will give us a perspective on two completely different systems. Hopefully by then your Ultra trifecta will have arrived too.

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1 minute ago, limniscate said:

@austinpop

 

Does this mean I'll get to hear the ISO-Regen in my system as well?

I'm in no hurry for it so austinpop can let anyone he knows keep it for a while.

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7 hours ago, austinpop said:

 

 

 

Having personally experienced the improvement wrought by this Ethernet regeneration, the next question is, indeed, where do manufacturers go from here?

 

@JohnSwenson, who is consistently honest and candid in these forums, has stated that this is an area he is interested in, and the science of what we're hearing is not well understood. I hope I paraphrased his views correctly.

 

Even if the science behind these improvements on the Ethernet is not yet baked, several questions arise going forward:

  1. what makes the SOtM sCLK-EX so special, as to surpass previous reclocked TCXO/OCXO switch offerings like the Pang, the AQvox, etc, that Roy had heard?
  2. how will SOtM modularize their offering? Right now, they have a single clock board - sCLK-EX - with 4 taps that they distribute both internally and externally. This approach is inherently limited by the length of the clock wire. What would make sense is to figure out a way to embed a fit-for-purpose sCLK-EX in each component. The current Ultra approach is wasteful and expensive - i.e. embed a full-size sCLK-EX board in each Ultra component.
  3. how will other manufacturers respond? And will we see new designs that compete with, and even exceed the SOtM solution, at equal or lower prices? As consumers, I sure hope so!

As I often like to say - it's an exciting time to be a computer audiophile! :D

I have not measured any of these clocks so I can't comment on their relative performance. But I can give some general observations.

 

First a clock in a real system can be very different than a clock being measured by itself. The phase noise of ALL clocks will change depending on noise on the power and ground network feeding the clock. So what is happening with other circuitry around a clock can significantly degrade its output from what you see in a spec sheet.

 

The lowest phase noise clocks are OCXOs, but not all OCXOs have very low phase noise. There are quite a few inexpensive OCXOs (less than say $150) that have worse phase noise than a 575.

 

The result is that just because two devices have OCXOs, does not mean they have identical jitter performance.

 

John S.

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13 minutes ago, JohnSwenson said:

The lowest phase noise clocks are OCXOs

 

Does "OCXO" stand for something we might learn from, or at least of interest ?

 

 

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1 hour ago, JohnSwenson said:

I have not measured any of these clocks so I can't comment on their relative performance. But I can give some general observations.

 

First a clock in a real system can be very different than a clock being measured by itself. The phase noise of ALL clocks will change depending on noise on the power and ground network feeding the clock. So what is happening with other circuitry around a clock can significantly degrade its output from what you see in a spec sheet.

 

The lowest phase noise clocks are OCXOs, but not all OCXOs have very low phase noise. There are quite a few inexpensive OCXOs (less than say $150) that have worse phase noise than a 575.

 

The result is that just because two devices have OCXOs, does not mean they have identical jitter performance.

 

John S.

 

13 minutes ago, JohnSwenson said:

OCXO stands for Oven Controlled Crystal Oscillator.

 

The hierarchy of crystal Oscillators:

 

XO  Crystal Oscilator

TCXO Temperature Compensated Crystal Oscilator

OCXO Oven Controlled Crystal Oscillator

 

What all this has to do with is how the frequency of an oscillator behaves as the temperature of the crystal varies. All crystals will change their frequency due to temperature changes. If you map these changes you get a curve that at low temperatures has a large change per small temperature delta, and at high temperatures a large change per small temperature delta, but at some intermediate temperature the "temperature coefficient" (TEMPCO) is zero.

 

If the operating temperature inside the equipment is not at this point, changes in temperature will change the frequency. The TCXO and OCXO are ways to make this better than a normal "uncompensated" crystal.

 

Note that these frequency changes are long term changes, sometimes referred to as drift. They are usually NOT the short term variations we call jitter. Thus optimizing for TEMPCO is not necessarily a good thing for audio.

 

The TCXO is an electronic circuit added to the oscillator. It turns out that you can change the frequency of an XO by changing the capacitance across it. The TCXO contains some form of temperature sensor that feeds a device that changes the capacitance across the crystal, the change in capacitance cancels out the change in temperature thus significantly lowering the TEMPCO, . But in doing so it increases the jitter, that temperature sensor and cpacitance changing circuit generates noise. This increases the jitter of the crystal. Thus TCXOs are usually not a good thing in digital audio, they are optimizing the wrong thing.

 

The operation of the OCXO is usually described as maintaining the temperature of the crystal so that the frequency doesn't depend on what is happening outside, the oven keeps the temperature stable. But this is not the whole story. The REAL purpose of the OCXO is to maintain the crystal at that temperature where the TEMPCO is zero, not just any old temperature. If the crystal is at the zero TEMPCO point then the temperature stability doesn't matter that much.

 

There is a big problem with this. The normal way a chunk of quartz is cut is called the AT cut, this has a zero TEMPCO temperature right around room temperature. This is fortuitous for non compensated crystals, but a real pain in the neck for OCXOs. If the crystal temperature is too high the system has to COOL the crystal, if too low heat it. This is quite complex and very expensive to do well.

 

The solution is to use a crystal cut called the SC cut. This has a zero TEMPCO point much higher than room temperature, so all you need is a heater, which is really easy to do (current through a resistor). This is why it is called an oven, it is always heating.

 

A side effect of the SC cut is that IF it is done right you get lower phase noise. But the inexpensive OCXOs put all the money into making the oven and skimp on the crystal quality, so they don't get particularly great phase noise. The ones that DO put money into the crystal can have the lowest phase noise of any oscillator, period.

 

So why doesn't anybody use an SC cut crystal without the oven? At room temperature the TEMPCO is SO far from the zero point that it would be almost useless.

 

I hope this gives a little insight into the world of crystal oscillators.

 

John S.

 

 

 

 

 

Thanks for these insights!

 

I cannot tell from the sCLK-EX Press release or its product page any mention of TCXO or OCXO, so one has to presume the claims come from the overall board design, not the actual crystal oscillator.

 

@JohnSwenson - where does the oscillator used in the ISO-Regen (the Crystek 575?) fit into the XO/TCXO/OCXO taxonomy?

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14 minutes ago, JohnSwenson said:

OCXO stands for Oven Controlled Crystal Oscillator

 

Wow, Thanks man for a fine explanation ! Another keeper for the pinned thread... if that ever comes to reality...

 

 

16 minutes ago, JohnSwenson said:

a curve that at low temperatures has a large change per small temperature delta, and at high temperatures a large change per small temperature delta, but at some intermediate temperature the "temperature coefficient" (TEMPCO) is zero.

 

Ok, I can visualize a wine-glass shaped curve (temp by delta f), but have a difficulty with it going to zero delta f ??

Is there some kind of thermal resonance with the crystal structure, or something ? I can see the variation, but the cause of the steady state eludes me...

 

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According to the sCLK-EX Press release, the sCLK-EX can be used for all digital devices that require clock signals such as DAC, USB host card, CD player, PC main board, LAN controller or others. The sCLK-EX can simultaneously use four (4) clock outputs so that one single sCLK-EX module can be used for various frequencies including the system clock, LAN port clock and USB clock in your PC.

 

Instead of modding a switch, I wonder what would happen if SOTM could modify the LAN controller on the server PC (say an Intel NUC) and the DAC???

 

So, PC server (modded LAN clock) -> direct ethernet connection to sms200Ultra -> DAC (modded clock). I believe all components in the digital chain would be synchronized that way, right?

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26 minutes ago, austinpop said:

I cannot tell from the sCLK-EX Press release or its product page any mention of TCXO or OCXO, so one has to presume the claims come from the overall board design, not the actual crystal oscillator.

I've been struggling with precisely that question.  Like I said earlier, we really have no technical performance data about sCLK-EX.  We do have very enthusiastic listening impressions.

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14 minutes ago, AmusedToD said:

Instead of modding a switch, I wonder what would happen if SOTM could modify the LAN controller on the server PC

I think that's exactly what @romaz is doing, transplanting sCLK-EX clock points to replace the motherboard clocks including the NIC.  I think messing with the clock in a DAC is way too radical.

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36 minutes ago, austinpop said:

 

 

Thanks for these insights!

 

I cannot tell from the sCLK-EX Press release or its product page any mention of TCXO or OCXO, so one has to presume the claims come from the overall board design, not the actual crystal oscillator.

 

@JohnSwenson - where does the oscillator used in the ISO-Regen (the Crystek 575?) fit into the XO/TCXO/OCXO taxonomy?

The 575 is an XO, but one of the best ones out there.

 

John S.

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31 minutes ago, JohnSwenson said:

The 575 is an XO, but one of the best ones out there.

John, where does VCXO fit in the hierarchy you described?

 

The specs of my Jeff Rowland Aeris say

20 bit dynamic range Voltage Controlled Crystal Oscillators (VCXO)
44.1 kHz and 48 kHz    < 1 picosecond RMS jitter

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13 minutes ago, rickca said:

John, where does VCXO fit in the hierarchy you described?

 

The specs of my Jeff Rowland Aeris say

20 bit dynamic range Voltage Controlled Crystal Oscillators (VCXO)
44.1 kHz and 48 kHz    < 1 picosecond RMS jitter

A VCXO is an XO with a circuit that varies the frequency from an externally applied voltage. Again noise on that voltage and the noise of the extra circuitry increase the jitter.

 

As mentioned before a single jitter number is almost useless. The number is an integration of the area under the phase noise curve. When doing the integration you have to choose the frequency range to use for the integration, for exactly the same oscillator changing the range can vary the "jitter number" by a factor 100!

 

Thus specifying a number without the lower and upper frequency limits is pretty much useless. You might be able to compare oscillators if the limits are exactly the same, but even then a true phase noise plot is much better.

 

The manufacturers love to choose the points to get the lowest number of course. If an oscillator really is good the manufacturer will usually specify the range to show it off. If not specified that is usually good indication that the device may not be the best and the manufacturer is playing some "specmenship" games.

 

John S.

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Today I experienced a major problem with my sms200Ultra and still can't fix it. I sent an email to SOTM some 6 hours ago and still no reply, so I decided to ask for some help here.

 

The sms200Ultra cannot connect to my local network for some reason as of today. I have tried all possible solutions I could think of (plugging and unplugging the ethernet cable numerous times, resetting the device, powering the device off and on, changing different ethernet cables, connecting the device either to my router or to my PC in bridged mode, and what not...). No solution. It simply can't establish a connection to my network (the router doesn't see it at all), nor can it connect to Eunhasu.

 

What appears to be the interesting part: when I take the sd card that holds the Linux OS out and connect the device to my network, the green LAN input light on the back of the device is ON. However, as soon as I plug the sd card back in and reset the device, the LAN input light is OFF. I figure this has to do with the OS in some way, perhaps it's bricked or whatever.

 

Any suggestions?

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2 minutes ago, limniscate said:

So that would have been 11 p.m. over there.  I'd give them some time to reply.

 

Absolutely, just asking if anyone else has had similar experiences.

 

What I didn't do (foolish of me) is make a backup of the sd card. I can't read it in Windows now because Windows wants me to format the card as soon as I plug it in.

 

Any suggestions?

 

 

 

 

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On 2017-6-6 at 9:50 AM, JohnSwenson said:

A VCXO is an XO with a circuit that varies the frequency from an externally applied voltage. Again noise on that voltage and the noise of the extra circuitry increase the jitter.

 

As mentioned before a single jitter number is almost useless. The number is an integration of the area under the phase noise curve. When doing the integration you have to choose the frequency range to use for the integration, for exactly the same oscillator changing the range can vary the "jitter number" by a factor 100!

 

Thus specifying a number without the lower and upper frequency limits is pretty much useless. You might be able to compare oscillators if the limits are exactly the same, but even then a true phase noise plot is much better.

 

The manufacturers love to choose the points to get the lowest number of course. If an oscillator really is good the manufacturer will usually specify the range to show it off. If not specified that is usually good indication that the device may not be the best and the manufacturer is playing some "specmenship" games.

 

John S.

John,

 

Can you show or reference a phase noise plot for us?

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On 5.06.2017 at 3:37 PM, greenleo said:

JCAT mentioned that they're going to introduce one.  But no sign yet.

Oh, it is coming very soon - still in June! 

 

On 5.06.2017 at 6:02 AM, ElviaCaprice said:

Hi Larry,

Not just JCAT, but any audiophile USB pcie card.  I can't make any sense of your attempt here, other than you used an old JCAT card with an outdated driver?  How could it sound worse?

 

If jumpers on the card were set properly then the only explanation that comes to my mind is that the dropouts were caused by USB selective suspend option which is enabled by default in Windows to save power when a USB device is not used. 

Regarding sound, I'd try with native MS driver. The optional NEC/Renesas driver is brighter and thinner sounding. 

 

Regards, 

Marcin

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Just a quick update, I managed to resolve the sms200Ultra issue. It was definitely software related. Somehow the OS got corrupted and I had to reinstall in order to get it working.

 

First I tried writing the OS image to the micro sd card using Win32 Disk Imager (while the micro sd card was plugged directly into my iMac card reader), and it didn't work. 

 

Today I bought a USB card reader and followed  the instructions posted here: http://docs.sotm-audio.com/doku.php?id=en:eunhasu:burn_sdcard_image#micro_sd_card_image_files

 

And it worked! The sms200Ultra is back online again!

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3 hours ago, Marcin_gps said:

Oh, it is coming very soon - still in June! 

 

 

If jumpers on the card were set properly then the only explanation that comes to my mind is that the dropouts were caused by USB selective suspend option which is enabled by default in Windows to save power when a USB device is not used. 

Regarding sound, I'd try with native MS driver. The optional NEC/Renesas driver is brighter and thinner sounding. 

 

Regards, 

Marcin

Hi Marcin,

 

Unfortunately the device has been returned to the owner, so there is no opportunity to test further.

 

I did test with both the native driver and the NEC driver, but I had to install the NEC driver early in the test in an effort to solve the stability problems.  

 

By the time I got it stable the NEC driver was installed. Indeed bright and thin is a good description.  At that point I gave up and reverted to the motherboard USB port.

 

Perhaps I'll have a chance to try again another time.

 

Thanks,

 

Larry

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