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Measuring jitter in 2020
- Thread starter Mike
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Interesting to go back and proving that gear that was supposed to fix a problem actually did not! I wonder how many reviewers actually praised those devices at the time.
As the article indicates, with specific tests (J-test) to measure jitter and newer DAC designs, jitter is no longer a problem or issue with modern components.
As the article indicates, with specific tests (J-test) to measure jitter and newer DAC designs, jitter is no longer a problem or issue with modern components.
+1 / word / fact
and, this only examines s/pdif data feeds. while not within the scope of the article, asynchronous DACs receiving a usb or ethernet signal is an alternate (better?) solution.
Puma Cat
Well-known member
JIitter continues to remain a problem, and with the increasing use of digital devices in our homes, e.g. so is....clock phase noise.
The SMPS that power almost everything these days, including video doorbells, smart alarms, thermostats, computer & networking systems, cause high-impedance leakage currents...these are extremely hard to measure, and were only discovered in Q4, 2017, just about 2 years ago. In fact, I know of only one engineer who has the test equipment to measure them; John Swenson.
The problem with these leakage currents is significantly impact clock phase noise. Increased clock phase noise causes its own problems, but it can also increase jitter.
Any cheap digital clock, e.g. those that are in commonplace a routers, cable modems, NAS, EoP adapters, Ethernet switches, fiber media convertors, etc., cause these problems. And if they are powered by SMPS, its even worse.
Then there is the impact of common mode noise, which can be problem with Ethernet cables.
So...if you think that noise components, e.g. jitter and/or clock phase or common mode noise are a thing of the past with respect to digital components...you may want to go back and think again.
The SMPS that power almost everything these days, including video doorbells, smart alarms, thermostats, computer & networking systems, cause high-impedance leakage currents...these are extremely hard to measure, and were only discovered in Q4, 2017, just about 2 years ago. In fact, I know of only one engineer who has the test equipment to measure them; John Swenson.
The problem with these leakage currents is significantly impact clock phase noise. Increased clock phase noise causes its own problems, but it can also increase jitter.
Any cheap digital clock, e.g. those that are in commonplace a routers, cable modems, NAS, EoP adapters, Ethernet switches, fiber media convertors, etc., cause these problems. And if they are powered by SMPS, its even worse.
Then there is the impact of common mode noise, which can be problem with Ethernet cables.
So...if you think that noise components, e.g. jitter and/or clock phase or common mode noise are a thing of the past with respect to digital components...you may want to go back and think again.
Puma Cat
Well-known member
Its going to depend on the USB cable and its construction/design to a degree, but in general, USB cables connected from a computer, NUC, etc. directly to a DAC are problematical. And more so if the USB receiver on the DAC does not provide galvanic isolation.
Better to use a network bridge in-between.
if i have read this post correctly it appears to conflate the two very different topics of electrical noise and jitter. the latter was the subject of the sterophile article. please, correct me if if have misread here.
jitter and phase noise are the exact same thing -- just measured differently as discussed here and more authoritatively here.
i agree electrical noise is an ongoing issue that needs to be addressed in the context of each individual system. otoh, i believe the separate issue of jitter (aka: phase noise) has been addressed with the asynchronous DAC.
i know of no current production high-end DAC that does not provide galvanic isolation (in fact, most quality electronics incorporate galvanic isolation as a means of protecting delicate circuity from electrical surges). that being said, galvanic isolation is not a complete solution for the elimination of electrical noise.
the state of the art in this respect is the lumin x1 which additionally offers optical isolation via an SFP input.
however, this is again a separate issue than that of jitter.
Puma Cat
Well-known member
I agree that jitter and clock phase noise are somewhat different transformations of the same noise component, however that's not the issue.
My point was in response to "jitter is no longer problem with modern components". If a system is connected to any kind of SMPS, e.g. computers, NUCs, NAS, routers, etc. or using components with cheap digital clocks, e.g. consumer-grade networking components, then there are still problems, particularly due to the impact of high-impedance leakage currents.
Feel free to read about jitter/timing/drift in the link below. Listen to the examples with exaggerated (manipulated) jitter/drift/timing issues and if you still believe that you are correct in what you are saying, feel free to post a comment at that site explaining why. That should generate an interesting discussion.
http://archimago.blogspot.com/2019/08/musings-demo-why-bits-are-bits-lets-not.html
fair enough... and there seems to be agreement that 1) jitter and phase-noise are the exact same thing measured differently and that 2) electrical noise is a bad thing.
however, you seem to be saying that in isolation the performance of a network device clock has an impact other clocks in the system and, specifically, the clock inside the DAC driving the conversion process. this is like saying the accuracy of my kitchen clock has an impact upon the accuracy of my wristwatch. i am at a loss to come up with the transmission mechanism that would cause this.
if i have understood your assertion correctly, could you describe exactly and specifically the transmission mechanism that causes the accuracy one computer clock to affect the accuracy of another -- and just so that we are only focusing on clocks here, let's assume that 100% of the electrical noise has been eliminated from the system including "high-impedance leakage currents"?
i am in no way trying to be contentious here -- i just want to learn. thanks!!
for anyone wishing to further geek-out on the subject of digital audio data clocking, here are two posts from a relevant thread on the roon community forum:
post from the programme manager at dCS
post from roon CTO
althought in the context of RAAT (roon advanced audio transport), the entire thread itself is also well worth a read for those wishing to further understand the subject and/or for anyone designing + implementing a digital front end.
post from the programme manager at dCS
post from roon CTO
althought in the context of RAAT (roon advanced audio transport), the entire thread itself is also well worth a read for those wishing to further understand the subject and/or for anyone designing + implementing a digital front end.
tube-vds
Member
- Joined
- Dec 1, 2015
- Messages
- 347
"Most manufacturers of audio equipment have little to no understanding of how networks function and how the network may or may not have an impact on actual playback. Sadly, this has a negative impact on the consumers who are forking over their hard-earned cash for solutions to problems which don’t actually exist."
Randy Myers
Well-known member
All of this probably comes into play. One of the main reasons that I very much prefer to keep my music on internal M.2 and SSD drives to eliminate other influences and affects on the signal traveling through all of these other devices. Also add to those listed above would be all of the cabling, unless you are in a position of replacing all of the ethernet and other cables in your house (don't forget those pesky little connectors and wall plates if you are trying to make all of this look good and "wife friendly")
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