LarsHP
Headphoneus Supremus
Not long ago, I said I was considering trying an external clock, but I want to get one that should improve the built-in, while not being super-expensive. This seems impossible.
So far, I have found some high-end clocks that measure great (Mutec Ref 10 Nano for instance), but are out-of-the-question expensive (three to four times the price of the R26). While people in this thread report good results using Leo Bodnar's clock (which is easy to power), I don't think it measures better than the one which is already in the R26, a so-called "femtosecond clock", given the LB clock is referred to as "sub-pico" clock. 1Hz deviation is only 72dB down at best, while the LHY clocks mentioned above are down in the 110dB region. That's a huge difference, in measurement terms at least. To me, spending about half the price of the R26 is also too much for "just" a clock.
The final nail in the coffin for me what that I stumbled on Golden Sound Audio's measurements, comparing the built-in clock (in the X26 Pro, which uses the same as the one in the R26) to the clock signal from the Audio Precision APx555 measurement device. The jitter got noticeably worse, getting the clock from the outside. Quote:
"Jitter performance here is truly excellent! A couple small spurs but other than that absolutely excellent. So, a question that many people will have: 'Is adding a 10Mhz clock worth it?' The short answer: No, 10Mhz clocks were never intended to improve jitter performance and almost never will do so. They are a tool to solve a problem in professional environments that does not exist in home setups. (...) As you can see, quite notably poorer jitter performance than without the 10Mhz clock. So why is this? The reason why a 10Mhz clock will worsen jitter isn’t to do with the particular 10Mhz clock used (though it will have an impact of course), even if you used the most perfect 10Mhz clock in the world you’re still going to get poorer performance simply due to how 10Mhz clocks are actually implemented. (...) A 10Mhz clock cannot be cleanly divided by 44.1khz or 48khz, and it cannot and does not directly run the DAC. Instead, the DAC uses a PLL system with the 10Mhz clock as the input reference, to output a 49.1520/45.1584Mhz (or whatever the required rate is) using its OWN clock internally. Your DACs clock is still the clock feeding the converter, it’s just being kept in time long term with the 10Mhz clock. 10Mhz clocks were never intended to improve jitter performance. They were intended to keep many devices in sync and prevent ‘clock drift’ over time in professional situations where you may have potentially dozens of DACs, ADCs, Processors etc running simultaneously and you do not want one to be running slower than the other and causing desync over time. As this could potentially cause issues in production or recording/outputting from several devices simultaneously."
Also note that, in the link, Golden Sound Audio demonstrate that noise from computers via USB going into the DAC degrades the performance:
"USB ‘cleanup’ devices come in all shapes and sizes, and whilst I think that many of them and their marketing claims are complete nonsense, it is a simple fact that noise on the USB connection can have a negative impact on a DAC, even if there is no ground loop present and regardless of grounding setup. And therefore when measuring devices I want to ensure that my USB source is not negatively impacting the measurement results. To do this, I use an intona 7055-C galvanic isolator which completely separates the DAC from the PC, meaning no noise can pass through. The X26 pro is affected by USB noise even from my fairly small PC and this can be shown in a few ways. We can see that there is some additional ultrasonic noise content present which disappears when we isolate the DAC. But noise can also have indirect effects on a DAC. For example the clocks in your DAC are called ‘Voltage Controlled Crystal Oscillators’ and they rely on being fed by a very clean, stable voltage to be accurate. If noise from the USB source contaminates this or the ground plane, there can be a degradation in performance."
Might the last quote be an explanation why an - on paper - "worse" clock could improve the sound? It does seem to underline the importance of the PSU.
EDIT - addition from a post here:
"... We have used the excellent Leo Bodnar GPS DSO £120 for years as,a master clock. Number of,satellites is irrelevant for audio clock use as long as the GPS locks. Main source for jitter in digital audio is, not the master clock, but CM noise entry or locally, contamination of the DAC, ADC, clock. Careful isolation with low capacité transformers, good PCB ground plane practice and use Shielded cables, can improve the noise and reduce jitter."
I expect "CM noise" is short for common mode noise.
So far, I have found some high-end clocks that measure great (Mutec Ref 10 Nano for instance), but are out-of-the-question expensive (three to four times the price of the R26). While people in this thread report good results using Leo Bodnar's clock (which is easy to power), I don't think it measures better than the one which is already in the R26, a so-called "femtosecond clock", given the LB clock is referred to as "sub-pico" clock. 1Hz deviation is only 72dB down at best, while the LHY clocks mentioned above are down in the 110dB region. That's a huge difference, in measurement terms at least. To me, spending about half the price of the R26 is also too much for "just" a clock.
The final nail in the coffin for me what that I stumbled on Golden Sound Audio's measurements, comparing the built-in clock (in the X26 Pro, which uses the same as the one in the R26) to the clock signal from the Audio Precision APx555 measurement device. The jitter got noticeably worse, getting the clock from the outside. Quote:
"Jitter performance here is truly excellent! A couple small spurs but other than that absolutely excellent. So, a question that many people will have: 'Is adding a 10Mhz clock worth it?' The short answer: No, 10Mhz clocks were never intended to improve jitter performance and almost never will do so. They are a tool to solve a problem in professional environments that does not exist in home setups. (...) As you can see, quite notably poorer jitter performance than without the 10Mhz clock. So why is this? The reason why a 10Mhz clock will worsen jitter isn’t to do with the particular 10Mhz clock used (though it will have an impact of course), even if you used the most perfect 10Mhz clock in the world you’re still going to get poorer performance simply due to how 10Mhz clocks are actually implemented. (...) A 10Mhz clock cannot be cleanly divided by 44.1khz or 48khz, and it cannot and does not directly run the DAC. Instead, the DAC uses a PLL system with the 10Mhz clock as the input reference, to output a 49.1520/45.1584Mhz (or whatever the required rate is) using its OWN clock internally. Your DACs clock is still the clock feeding the converter, it’s just being kept in time long term with the 10Mhz clock. 10Mhz clocks were never intended to improve jitter performance. They were intended to keep many devices in sync and prevent ‘clock drift’ over time in professional situations where you may have potentially dozens of DACs, ADCs, Processors etc running simultaneously and you do not want one to be running slower than the other and causing desync over time. As this could potentially cause issues in production or recording/outputting from several devices simultaneously."
Also note that, in the link, Golden Sound Audio demonstrate that noise from computers via USB going into the DAC degrades the performance:
"USB ‘cleanup’ devices come in all shapes and sizes, and whilst I think that many of them and their marketing claims are complete nonsense, it is a simple fact that noise on the USB connection can have a negative impact on a DAC, even if there is no ground loop present and regardless of grounding setup. And therefore when measuring devices I want to ensure that my USB source is not negatively impacting the measurement results. To do this, I use an intona 7055-C galvanic isolator which completely separates the DAC from the PC, meaning no noise can pass through. The X26 pro is affected by USB noise even from my fairly small PC and this can be shown in a few ways. We can see that there is some additional ultrasonic noise content present which disappears when we isolate the DAC. But noise can also have indirect effects on a DAC. For example the clocks in your DAC are called ‘Voltage Controlled Crystal Oscillators’ and they rely on being fed by a very clean, stable voltage to be accurate. If noise from the USB source contaminates this or the ground plane, there can be a degradation in performance."
Might the last quote be an explanation why an - on paper - "worse" clock could improve the sound? It does seem to underline the importance of the PSU.
EDIT - addition from a post here:
"... We have used the excellent Leo Bodnar GPS DSO £120 for years as,a master clock. Number of,satellites is irrelevant for audio clock use as long as the GPS locks. Main source for jitter in digital audio is, not the master clock, but CM noise entry or locally, contamination of the DAC, ADC, clock. Careful isolation with low capacité transformers, good PCB ground plane practice and use Shielded cables, can improve the noise and reduce jitter."
I expect "CM noise" is short for common mode noise.
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