[Jake2]

I wonder whether the R26 and many other DACs have spurs due to their internal clocks so external clocks can end up giving a better sound. There has to be a plausible explanation somewhere,,,,given the femto clock in the R26.

That is exactly what the sole jitter plot I’ve seen of the R26 shows… lots of side spurs on an otherwise low jitter floor plot. To the extent it prompted the reviewer, Wolf (a character who makes lots of blunt assessments) to comment that he wondered if a Gustard did this intentionally to sell more of their external clocks like the C18.

@camrector What is annoying is he didn’t actually provide a full x-axis zoom into the 12khz signal (despite titling the second chart 12khz zoom, as that one just zoomed out slightly on the Y axis to see the floor) that explodes out the centre spike so you see the level of jitter at closer offsets like 10hz and below (ie phase noise), like he did for that A26 plot I previously posted and marked up. I expect that, as with the A26, the low offset jitter would be soaring well above Amit’s theoretical audibility threshold of -115dB, potentially more so than the A26 given the sidelobe activity,

I have considered asking him for the true 12khz x-axis zoom plot if he still has it or can generate it from his files - it’d be interesting to see.

https://www.l7audiolab.com/f/gustard-r26/ Need to use Google translate.

 

[Clivem2]

That is exactly what the sole jitter plot I’ve seen of the R26 shows… lots of side spurs on an otherwise low jitter floor plot. To the extent it prompted the reviewer, Wolf (a character who makes lots of blunt assessments) to comment that he wondered if a Gustard did this intentionally to sell more of their external clocks like the C18.

@camrector What is annoying is he didn’t actually provide a full x-axis zoom into the 12khz signal (despite titling the second chart 12khz zoom, as that one just zoomed out slightly on the Y axis to see the floor) that explodes out the centre spike so you see the level of jitter at closer offsets like 10hz and below (ie phase noise), like he did for that A26 plot I previously posted amd marked up. I expect that, as with the A26, the low offset jitter would be soaring well above Amit’s theoretical audibility threshold of -115dB, potentially more so than the A26 given the sidelobe activity,

I have considered asking him for the true 12khz x-axis zoom plot if he still has it or can generate it from his files - it’d be interesting to see.

https://www.l7audiolab.com/f/gustard-r26/ Need to use Google translate.

That makes sense. Having been pilloried for using such a lousy PN performing clock, it’s becoming clearer why it works and that PN isn’t necessarily the critical sole criterion.

 

[Clivem2]

That makes sense. Having been pilloried for using such a lousy PN performing clock, it’s becoming clearer why it works and that PN isn’t necessarily the critical sole criterion.

To follow up…I can understand that connecting an external clock is fraught with jitter issues, this is why it seemed to me that an external clock for a single device shouldn’t really be a good idea. I get why a single click for multiple devices is a good idea. Presumably the R26 clock must be quite hobbled as external clocks work so well, given the jitter issues they have to overcome. That said the R26 on its own still sounds great.

I’ll try to describe what I feel the is immediately character the LB clock brings with an LMR400 cable. Overwhelmingly it’s a meaty sound, there’s great depth which outdoes my rather good record decks. Resolution is very good and not in an obvious way..so often resolution is faux, created by frequency peaks and imbalances - here it’s deep in the soundstage. There’s no harshness at all, so much so that it’s uncanny, yet there’s plenty of treble extension.

 

[Jake2]

To follow up…I can understand that connecting an external clock is fraught with jitter issues, this is why it seemed to me that an external clock for a single device shouldn’t really be a good idea. I get why a single click for multiple devices is a good idea. Presumably the R26 clock must be quite hobbled as external clocks work so well, given the jitter issues they have to overcome. That said the R26 on its own still sounds great.

I’ll try to describe what I feel the is immediately character the LB clock brings with an LMR400 cable. Overwhelmingly it’s a meaty sound, there’s great depth which outdoes my rather good record decks. Resolution is very good and not in an obvious way..so often resolution is faux, created by frequency peaks and imbalances - here it’s deep in the soundstage. There’s no harshness at all, so much so that it’s uncanny, yet there’s plenty of treble extension.

I agree re your general point that there can be faux resolution sometimes with DACs (often through etched transient edges that lack the fine nuance of the recorded signal), and although it’s early days with the LB for me I can relate to several aspects of its sound you describe.

I would however take issue with your description of the R26 as hobbled. A DAC doesn’t need to be poor performing in order to benefit from an external clock. Many very, very good DACs including Audio Gd’s top models and the A26, which is cleaner measuring in many respects then the R26, have been found to improve a lot through quality external clocks. More to the point as well all know the R26 has been reviewed very positively by quite a number of people without external clocks relative to other DACs in its price range and beyond. But I would agree there may be some quirks to the R26’s jitter plot that means it benefits from the LB more than other DACs.

 

[Clivem2]

I agree re your general point that there can be faux resolution sometimes (often through etched transient edges that lack the fine nuance of the recorded signal), and although it’s early days with the LB for me I can relate to several aspects of its sound you describe.

I would however take issue with your description of the R26 as hobbled. A DAC doesn’t need to be poor performing in order to benefit from an external clock. Many very, very good DACs incl including Audio Gd’s top models and the A26, which is cleaner measuring in many respects then the R26, have been found to improve a lot through quality external clocks. More to the point as well all know the R26 has been reviewed very positively by quite a number of people without external clocks relative to other DACs in its price range and beyond. But I would agree there may be some quirks to the R26’s jitter plot that means it benefits for from the LB than other DACs.

TBH I struggled with the word “hobbled” as I typed it. I couldn’t come up with a better term. What’s in my mind is that external clocks have a lot more challenges than internal ones which are “close to the action”. Surely the external clocks must first of all overcome the downside of being external. I’m sure I don’t understand enough of the technicalities, it just seems unfortunate that what could be an excellent internal clock can be improved on even in the face of the adversity that comes with being external…maybe being external isn’t all downside, ie power supply and RF shielding.

 

[Jake2]

What is clear is it is a complicated space with many variables, including the jitter performance / characteristics of:

• the external clock and DAC (the inherent jitter characteristics of their oscillators and their levels of RFI and power supply noise which may mess with this)
• the full transmission line that connects one oscillator to the other (incl the Clock’s internal circuitry from sine-square wave conversion, if applicable, through the clock BNC jack/cable BNC, the cable itself with its particular internal reflectivity due to its conductor and dielectric materials along with its shielding characteristics, a second BNC junction with plugs and jacks likely made of different materials in an imperfect mechanical and conductive union, then the DAC’s clock receiving circuit and/or square/sine conversion)
• and last but far from least the performance of the PLL or clock synthesiser In the DAC. Anecdotally at least the K2 adds hardly any jitter in using a master clock signal to synthesise the clock frequencies used by the DAC. Whereas historically it seems this synthesisation step did add a lot of jitter leading to generalisations that external clocks can only add jitter, which may have been truer then but may now be outdated.

I should also note there are different types of jitter where some maybe more audible than others due to their nature and/or their levels relative to the audio signal. With phase noise the important thing to keep in mind is it’s a decibel measure relative to the carrier signal, at a specified frequency offset, essentially measuring the volume offset, an X,Y offset coordinate if you will. The carrier signal in the case of the master clock is the clock signal at 10 MHz set at a fixed maximum amplitude, or in the case of music it is each frequency of a note I.e. a hundred or a thousand carrier signals across the frequency spectrum of the music (though apparently psycho acoustic models collapse this down into a smaller number of buckets of frequencies that we perceive distinctly). As the volume level of the music continuously varies and is rarely at maximum there is a suggestion by some folk (incl Amir of you know where) that the difference between phase noise beyond/between say -70dBc and lower levels (eg -120dBc) is very unlikely to be audible because music is only rarely at or near peak levels that would allow sufficient dynamic range/SNR for jitter level differences to be fully displayed. That has some intuitive appeal to me however I’m not sure I quite accept this, I feel it is yet another simplification, as it doesn’t align to my experience with multiple clocks, DACs and DDCs, or that of many others who find worthwhile/dramatic audible improvements as they compare two expansive clocks with sub -115dBc/1hz phase noise only a few dBc apart. Having said that this logic may still contain some truths that are relevant here and help explain the variability in audible difference.

My point - and sorry it took me a while to get to it - is DACs and external clocks are a pretty damn complex system where hard generalisations are going to be wrong as often as they’re right, but where some rules of thumb may help us users stack the odds in our favour for getting a good result.

I pity the poor new R26 owners landing on this thread looking for advice on how to set it up…

 

[Jake2]

What is clear is it is a complicated space with many variables, including the jitter performance / characteristics of:

• the external clock and DAC (the inherent jitter characteristics of their oscillators and their levels of RFI and power supply noise which may mess with this)
• the full transmission line that connects one oscillator to the other (incl the Clock’s internal circuitry from sine-square wave conversion, if applicable, through the clock BNC jack/cable BNC, the cable itself with its particular internal reflectivity due to its conductor and dielectric materials along with its shielding characteristics, a second BNC junction with plugs and jacks likely made of different materials in an imperfect mechanical and conductive union, then the DAC’s clock receiving circuit and/or square/sine conversion)
• and last but far from least the performance of the PLL or clock synthesiser In the DAC. Anecdotally at least the K2 adds hardly any jitter in using a master clock signal to synthesise the clock frequencies used by the DAC. Whereas historically it seems this synthesisation step did add a lot of jitter leading to generalisations that external clocks can only add jitter, which may have been truer then but may now be outdated.

I should also note there are different types of jitter where some maybe more audible than others due to their nature and/or their levels relative to the audio signal. With phase noise the important thing to keep in mind is it’s a decibel measure relative to the carrier signal, at a specified frequency offset, essentially measuring the volume offset, an X,Y offset coordinate if you will. The carrier signal in the case of the master clock is the clock signal at 10 MHz set at a fixed maximum amplitude, or in the case of music it is each frequency of a note I.e. a hundred or a thousand carrier signals across the frequency spectrum of the music (though apparently psycho acoustic models collapse this down into a smaller number of buckets of frequencies that we perceive distinctly). As the volume level of the music continuously varies and is rarely at maximum there is a suggestion by some folk (incl Amir of you know where) that the difference between phase noise beyond/between say -70dBc and lower levels (eg -120dBc) is very unlikely to be audible because music is only rarely at or near peak levels that would allow sufficient dynamic range/SNR for jitter level differences to be fully displayed. That has some intuitive appeal to me however I’m not sure I quite accept this, I feel it is yet another simplification, as it doesn’t align to my experience with multiple clocks, DACs and DDCs, or that of many others who find worthwhile/dramatic audible improvements as they compare two expansive clocks with sub -115dBc/1hz phase noise only a few dBc apart. Having said that this logic may still contain some truths that are relevant here and help explain the variability in audible difference.

My point - and sorry it took me a while to get to it - is DACs and external clocks are a pretty damn complex system where hard generalisations are going to be wrong as often as they’re right, but where some rules of thumb may help us users stack the odds in our favour for getting a good result.

I pity the poor new R26 owners landing on this thread looking for advice on how to set it up…

I’d be interested in Tony from Coherent’s take on the above.. hopefully I’m at least warm!

 

[Stellabagpuss]

Props to you Guys.... This is exactly the most progressive talk about clocks l've read for a long time. It's refreshing to read your looking into reasons,rather than falling back on the world according to ASR.
Well done..Keep it up...and keep educating us.

 

[camrector]

To follow up…I can understand that connecting an external clock is fraught with jitter issues, this is why it seemed to me that an external clock for a single device shouldn’t really be a good idea. I get why a single click for multiple devices is a good idea. Presumably the R26 clock must be quite hobbled as external clocks work so well, given the jitter issues they have to overcome. That said the R26 on its own still sounds great.

I’ll try to describe what I feel the is immediately character the LB clock brings with an LMR400 cable. Overwhelmingly it’s a meaty sound, there’s great depth which outdoes my rather good record decks. Resolution is very good and not in an obvious way..so often resolution is faux, created by frequency peaks and imbalances - here it’s deep in the soundstage. There’s no harshness at all, so much so that it’s uncanny, yet there’s plenty of treble extension.

Presumably the R26 clock must be quite hobbled as external clocks work so well, given the jitter issues they have to overcome.

But this isn’t true. External clocks do not lower jitter. They increase it. Plus plenty of R26 users have experienced zero benefit from external clocks.

 

[Dandoudou]

I pity the poor new R26 owners landing on this thread looking for advice on how to set it up…

They will start as newbies with page 1 of the thread. The most valorous will end with a Ph.D. from Gustard's Academy for imputing the BT circuity of the DAC, implanting the LB clock in its heat, shielding its internal organs, and Fo.Quing it…

 

[Clivem2]

But this isn’t true. External clocks do not lower jitter. They increase it. Plus plenty of R26 users have experienced zero benefit from external clocks.

The increasing jitter part was my point. The remote cable is said to increase jitter so external clocks start with a huge disadvantage. As Jake has said, it’s a complex system…not that I know but I’m picking up on what others think. To simply believe external clocks can’t be an improvement just doesn’t stack up. Can I prove this with measurements? Absolutely not, this is not my area of expertise so I’m coming at this from what I hear to verify what the two very differentiated technical sides are saying.

 

[camrector]

The increasing jitter part was my point. The remote cable is said to increase jitter so external clocks start with a huge disadvantage. As Jake has said, it’s a complex system…not that I know but I’m picking up on what others think. To simply believe external clocks can’t be an improvement just doesn’t stack up. Can I prove this with measurements? Absolutely not, this is not my area of expertise so I’m coming at this from what I hear to verify what the two very differentiated technical sides are saying.

It’s an easily explained complex system.
I shared a video to help everyone understand the process better.
Here is a great article too.

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

“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”

 

[Stellabagpuss]

lnteresting....but l wonder if the same view point is held,this was published in 2010.

 

[camrector]

lnteresting....but l wonder if the same view point is held,this was published in 2010.

No need to wonder unless someone changed digital audio to no longer be based on sampling and forgot to tell the world.
The science, math and implementation hasn’t changed either.

“So, although sonic differences may be perceived when using an external clock as compared to running on an internal clock, and those differences may even seem quite pleasant in some situations, this is entirely due to added intermodulation distortions and other clock‑recovery related artifacts rather than any real audio benefits, as the test plots illustrate.”

If you like the sound of your clock go buy one of these and save a ton of money!
https://diyaudiostore.com/products/h2-harmonic-generator

 

[Clivem2]

No need to wonder unless someone changed digital audio to no longer be based on sampling and forgot to tell the world.
The science, math and implementation hasn’t changed either.

“So, although sonic differences may be perceived when using an external clock as compared to running on an internal clock, and those differences may even seem quite pleasant in some situations, this is entirely due to added intermodulation distortions and other clock‑recovery related artifacts rather than any real audio benefits, as the test plots illustrate.”

If you like the sound of your clock go buy one of these and save a ton of money!
https://diyaudiostore.com/products/h2-harmonic-generator

Are you in the camp that say the stock R26 sounds the same as other DACs that measure as most modern DACs and are essentially perfect? I gather whilst the R26 may not measure the best, any difference will be inaudible.