If there are errors, the output bits don't match the input bits, and thus the cable is broken. Wrong bits will be very noticeable in either audio or video.
If there is jitter, it should be solved by the receiving side buffer.
There are error corrections so errors usually are not the problem. Besides, my guess is the audio data is interleaved so even if there are errors, which should be very small, real small, there should be an algorithm to interpolate, like they do in CD playback.
As for jitter, it's easy to solve in theory but much harder in implementation.
Finally got to read not all of it but some of it. I don't mean to be a bad guy, or do mean I don't know, but here are my comments:
1. The distortion tests were probably done at one frequency or just a few freq. I don't think that is enough to draw any condition.
2. In my experience, looking at the freq. spectrum of Spectrum analyzer, it's never stable, it's sort of moving up and down. And the reason it's moving up and down because of the changing phase or changing in time domain. So he was probably doing an average which pretty much discarding all the phase information. (And also a single freq). And, here we go again, the phase relation is very important. And personally I don't think you can measure any thing different in this setup if the USB DAC is asynchronous mode.
3. He did show the frequency response plot of all three cable and they do look very similar. Again he probably used averaging so it could hide a lot of important information. I personally don't expect difference in freq. response since it's is only a function of the analog DAC stage.
Anyway, my point is he only present data on the freq. domain, at one freq, but I think the reason all the cables sound different lies in the time domain. The test was probably done using averaging and I think that may have invalidated it.
But there is a test that can absolutely capture the difference in time domain, but you have to build your own jig or even your own DAC. I am not telling though. The setup in the link is not good enough to capture things happening in the time domain.
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If I can find them. It's been years and 1000s of threads ago.
Point is, if you are at all DIY in electronics this is a simple problem and a simple test. If I can figure it out, anyone here can. The software is free, you already own the hardware.
I tried to find the USB tests with limited success. We did go around and around about SPDIF 10 years ago and tests where done there. Using USB to SPDIF signal flow (should be awful) we were able to show that USB can be super clean and no jitter shows up on the analog output. I also showed that if there is jitter, such as in a jitter test signal, it's easy to see.
RF Attenuators = Jitter Reducers
RF Attenuators = Jitter Reducers
RF Attenuators = Jitter Reducers
When one cable causes more noise or jitter than another, you'll see it in the measurements. You don't even need an AP analyzer to do it. Ground loops show up too, big time.
Think you have a cable that's worse than others? Test it! It will be easy to see in the tests and you'll have some bragging rights. Otherwise it's all just hand waving.
RF Attenuators = Jitter Reducers
RF Attenuators = Jitter Reducers
RF Attenuators = Jitter Reducers
When one cable causes more noise or jitter than another, you'll see it in the measurements. You don't even need an AP analyzer to do it. Ground loops show up too, big time.
Think you have a cable that's worse than others? Test it! It will be easy to see in the tests and you'll have some bragging rights. Otherwise it's all just hand waving.
Dear JP
You shouldn’t publish confidential data (Rule #9) diyAudio Rules
I’ve underlined the part of your post which refers to the non confidential source.
Now, regarding ESD protection and EMI filtered USB interface:
https://assets.nexperia.com/documents/application-note/AN11882.pdf
http://www.scs-europe.net/dlib/2016/ecms2016acceptedpapers/0270-is_ECMS_0135.pdf
The USB Interface from EMC Point of View | Wurth Elektronik: Electronic & Electromechanical Components - Standard Parts > Products > Application Notes
George
It seems like a lot of tests measure jitter at a single tone or frequency. I am not sure that is enough. And I've seen some measurements on line and they tend to underestimate how difficult it is to capture transient responses in the time domain. I think you need some pretty sophisticated equipment and setup to do that. A laptop and a scope probably is not enough. You have to synchronize the signal sending from the laptop and know how to trigger that on the scope to capture the effect.
Andy2, I don't want to invoke your location as your argument is made out of ignorance about the nature of jitter, and why single tones are highly effective in elucidating the hardware issues at play.
The consequences of jitter change with frequency, but the nature of that jitter affects the entire data stream.
The consequences of jitter change with frequency, but the nature of that jitter affects the entire data stream.
I guess I don't want to argue with your ignorance either since you underestimate how difficult it is to measure the effect of jitter on the analog signal. It's not a simple one-to-one relationship. It's digital then converted to analog. It's complicated and you need years to experience to understand. I've read a bunch of books to understand so I am not going to explain to you in a few sentences.
USB Made Simple
The takeaway is that USB HS specifies active D+/D- 45ohm termination to shield/ground.
It seems that USB LS/USB HS termination is not specified.
On initial inspection it seems that In datasheets/EVM for the likes of PCM270* and other USB receiver/dsp/dac LSI's solutions D+/D- termination is not mentioned.
Also LS/FS identification is reliant on 1.5k ohms pull up resistance from 3.3V supply....unbalancing ?.
Dan.
The takeaway is that USB HS specifies active D+/D- 45ohm termination to shield/ground.
It seems that USB LS/USB HS termination is not specified.
On initial inspection it seems that In datasheets/EVM for the likes of PCM270* and other USB receiver/dsp/dac LSI's solutions D+/D- termination is not mentioned.
Also LS/FS identification is reliant on 1.5k ohms pull up resistance from 3.3V supply....unbalancing ?.
Dan.
Jitter in the data transfer/replay system ultimately presents/reproduces as movement of the apparent sound source.
Serial audio data is transferred as L/R packets of data with inherent timing variations.
Timing variations of the decoded analog output will ultimately present/reproduce as L/R positional movement/uncertainty AND distance positional movement/uncertainty.
Perfect data transfer time certainty reproduces as point source, time variant digital systems reproduce as noisy spheroid.
Vinyl systems preserve L/R and distance coherence at the expense of shaped broadband noise...this causes shaped L/R/distance uncertainty which is subjectively quite different to digital replay system L/R/distance subjective uncertainty.
Digital audio replay systems of course have some inherent jitter caused artifacts......the nature of these (usually) very low level artifacts is what subjectively differentiates digital audio reproduction systems.
I find that these 'subtle' artifacts can be modified at will, most certainly in the case of these typical 'consumer/prosumer' receiver equipment undefined USB cables and cable loadings.
Dan.
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Funny, I thought it was pretty classic signal theory that can be elucidated from throwing a modulation signal onto a clock and watching it propagate. And USB transmission jitter is highly mitigated by buffering, provided the receiver can catch the signal. Digital transmission is pretty robust against timing errors. If it cannot, we have so much bigger problems than whether a USB cable can have an audible effect. The jitter we're most worried about is at the DAC. The ADC is probably even more important, but we usually don't have any control over that end of the chain.
A bunch of books should long have told you that, though, which makes your point even more problematic. I'll give you some help though -- Julian Dunn wrote some excellent papers/book on the subject that will help out tremendously.
We went over that whole "It's a tone not a complex signal" years ago. As DPH says, jitter will affect any signal. The advantage of a sine is that it makes the jitter easy to see. You could use square, saw or triangle if you want more "complex."
It's a similar argument to data transport. Sending a sine wave as a data stream is not easier not more complex that anything else. It's super easy to send Redbook audio or even 96/24 over USB or SPDIF. Bit perfect. Try it for yourself.
It's a similar argument to data transport. Sending a sine wave as a data stream is not easier not more complex that anything else. It's super easy to send Redbook audio or even 96/24 over USB or SPDIF. Bit perfect. Try it for yourself.
Now you're just resorting to hand waving. You won't to any tests, you claim they are too difficult and we don't understand them anyway. You present no proof, no evidence, nothing. How do you expect to be taken seriously?
Well it seems like you're too easy to believe a bunch of tests without asking any questions. Trust no one lols'.
The USB DAC architecture is asynchronous. The analog output is not synchronized to the incoming USB data stream. Like I said, it's not a simple one to one relationship. All the test setup I've seen are not adequate to test these. Besides, I don't think they understand the architecture well enough to setup the test. It's not as simple as sending something from the laptop to the USB DAC then measure the analog that is completely uncorelated to the incoming USB data. You have to be able to figure out how "catch" the analog output.
Also a lot of these tests were not done in a control manner. I mean they send something from their labtop without knowing what the actual jitter amount which could be anything. If you don't know your input parameters, how in the world can you characterize the output? It's as simple as that. I've read about these on-line test and I don't even know what the setup, the credibility of those who doing the test, the equipment setup and so on...
So the question is if you're too easy to be fool, then maybe you shouldn't be taken seriously. A lot of non-technical people they see a bunch of fancy graph and plots and they start salivate.
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