It's a digital signal. If there are errors, the output bits aren't the same as the input bits.
There is no such thing as a "small error" - either a bit is properly transmitted, or it's not.
As for jitter, the receiving side needs to buffer the incoming bits to properly form a bitstream anyway, so either the jitter is so bad it results in an erroneous bitstream, or the bitstream is perfect.
If it doesn't work this way, the receiving side ****** up its buffering.
I'm thinking, based on history, that he's monitoring the thread but making light of it. Pretty much any cables thread ends up, well... I'll leave it there.
Andy. Really? Do you really believe that it's so difficult to see jitter and noise in the output of a DAC? It isn't, as I showed you in that thread from so many years ago. If jitter and noise are there, you will see them. Measuring them is not too complicated for me or the average person on this forum. I've shown as much, I've shown that you can see that jitter. SY showed it too. Somewhere (maybe in that thread) I posted measurements of a cheap CMedia USB chip that was noisy, jittery and had high harmonics. All those things can be measured. Telling is it's all to complicated for mere mortals like us is just silly.
Jitter and noise can be measured. It's not difficult to do. If you have USB cables that are different in jitter and noise (they do exist) - show us. Otherwise it's just hand waving.
Jitter and noise can be measured. It's not difficult to do. If you have USB cables that are different in jitter and noise (they do exist) - show us. Otherwise it's just hand waving.
No, it's not the million dollar question. It's easy to measure and see noise in digital transports like USB. That's a good thing, not a bad thing. When there is a problem, we can find it.
Now, if you want to come up with some reason that fancy cables are better than normal cables, then citing unknown tests that are so difficult to understand it's not worth explaining them - that's one way to avoid real evidence. It not a ruse that's likely to get any takers, but nice try.
Now, if you want to come up with some reason that fancy cables are better than normal cables, then citing unknown tests that are so difficult to understand it's not worth explaining them - that's one way to avoid real evidence. It not a ruse that's likely to get any takers, but nice try.
All this talk about jitter on USB & it being seen on analogue output seems to ignore how USB works? USB is (mostly) differential signalling & what happens if there is skew differences (jitter) between D+ & D- signal? Does it become common mode noise at the USB differential receiver? How is CM noise handled/mitigated within USB audio devices? How is it tested for at analogue outputs of USB DACs?
CM noise was already mentioned at the start of the thread as one of the possible differences between cables. Unequal lengths of D+ D- signal lines is one possible difference between cables
Don't know what audible difference this makes but unless it is being tested for I don't see how it can be ignored
CM noise was already mentioned at the start of the thread as one of the possible differences between cables. Unequal lengths of D+ D- signal lines is one possible difference between cables
Don't know what audible difference this makes but unless it is being tested for I don't see how it can be ignored
No. In any competent device the USB data is buffered and clocked out synchronously to the LOCAL clock only. What happens on the USB interface, short of data corruption, has nothing to do with the digital output. In addition, you will see many devices galvanically isolate the I2S outputs of the USB interface IC. I doubt that is necessary but it certainly pokes all kinds of holes in your pet theory.
What's that got to do with CM noise?
I thought it was analogue output that was being considered most important here? So, I'm afraid your objections are off the point
It's not my pet theory - CM noise in differential & pseudo-differential signals (USB is two SE communication lines) is a well know & well studied phenomena. The causes of CM noise in such environments are well known & twisted pair pitch & consistency are among one such cause as is skew in risetimes - all of which are possible differences between cables.
So are you saying galvanic isolation is of use in CM noise elimination or not - I don't quite follow your rant?
Care to directly answer any of the questions I posed in my post - what happens to signal skew at the USB receiver, for instance?
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You need to understand how the entire system works first. You can google it all. Feel free to ignore my previous post. Sometimes I forget that this is a total waste of time.
You either get the frame successfully or you do not, period, end of story. Any other effects of coupled noise are not unique to USB and present just the same in any other interconnect.
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OK, so is EMI an issue with USB cables - why wouldn't different cables have different EMI spectra profiles?
Wire pairs can be shielded or not, Cable Shielding can be foil, mesh, with/without drain wire.
I don't know if some USB cables sound different. I know when I tried ferrites on USB cables it changed the sound but not to my liking & when I used a USB cable which had a ferrite compound outer layer, it noticeably reduced background noise but maybe lessened some detail - can't remember now, it was a while ago, so I don't discount that some cables could strike the right balance?
Oh & that ferrite USB cable has a datasheet showing measurements.
It seems to me that there are possible differences between USB cables in lots of characteristics but what is being argued here is that these differences leave the analogue output of USB DACs unaffected. Can this be stated for a fact? How has CM noise, EMI been measured in the analogue output?
Oh, don't worry, I understand the ENTIRE system - you seem to only want to focus on digital signal transmission/receipt.
If only the world was so simple!! Google can help you understand some of the complexity you are missing but it also might be a wast of time for you?
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No, it's not the million dollar question. It's easy to measure and see noise in digital transports like USB. That's a good thing, not a bad thing. When there is a problem, we can find it.
Now, if you want to come up with some reason that fancy cables are better than normal cables, then citing unknown tests that are so difficult to understand it's not worth explaining them - that's one way to avoid real evidence. It not a ruse that's likely to get any takers, but nice try.
You seem to provide a lot of entertainment, but short of know how.
To me USB are very imperfect cables because they share a power supply 5V and two digital signals instead of single ended, + the wires are crap inside like cheap headphones.
It is futile to ask for a great natural sound from such a flawed medium. I see it as unattainable, in desperation you might use the smoother sounding wires. I don't think there is a middle ground, however I don't see any issue with common market well designed USB's.
Stay away from apple products, they make the worst USB cables. (as well as headphones and sound outputs! my quality rating -10/1000 for Ipods) This also extends to the mac pro, which has horrendous and horrible blue-ray hdmi sound output for watching movies, shame on apple. I have a recent mac book pro and the other slim one.
If you look at Locus design the really nailed down the question. I use a similar hifi USB cable without any sound complain
Locus Design Group - Locus Design Group - Locus Design Nucleus USB cable
Read the text, it explains much!
Andy, the rise time etc. is dependent of inter-capacitance.
I completely ignore the type of digital signal sent in the USB cable, however the input and output chips should deal with filter transformers/attenuators the noise and problems of capacitance, and jitter to reassemble bits and re-clock them with a buffer.
The loss of resolution can be counted, there are machines out there which can verify each input from known sources and reassemble date and count delayed/problems. There are unfortunately/fortunately anti-skips, sorry for my jargon. This prevents more clics/pops and ultrasonic sounds when there are errors, and is filled with approximation or silences.
This is the only thing you can hear for sound degradation of the USB.
Many culprits, the 5V power, the lack of proper shield, mechanical noises and radio interferences, imprecise signal generators and noise sources.
I completely ignore the type of digital signal sent in the USB cable, however the input and output chips should deal with filter transformers/attenuators the noise and problems of capacitance, and jitter to reassemble bits and re-clock them with a buffer.
The loss of resolution can be counted, there are machines out there which can verify each input from known sources and reassemble date and count delayed/problems. There are unfortunately/fortunately anti-skips, sorry for my jargon. This prevents more clics/pops and ultrasonic sounds when there are errors, and is filled with approximation or silences.
This is the only thing you can hear for sound degradation of the USB.
Many culprits, the 5V power, the lack of proper shield, mechanical noises and radio interferences, imprecise signal generators and noise sources.
For one, you don't seem to grasp where and when the signal is critical and when it is asynchronous. You are asking questions that make no sense if you actually understand and have experience using these interfaces.
You are so worried about the effects of the cable connection when this has nothing to do with USB specifically and applies to any non-optical interconnect.
Your initial post has a lot of flaws in it. Point number 3 especially is completely incorrect and not how "clock recovery" works in asynchronous mode USB Audio Class devices which now dominate the market. This has been beaten to death in hundreds of other threads already over the past 10+ years.
We had to suffer through so many years of idiocy about SPDIF cables with cries of "BUT BUT... THE CLOCK IS TRANSMITTED OVER THE CABLE, BITS AREN'T BITS". Now that asynchronous interfaces have solved this problem, new and more nuanced excuses have to be invented.
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