Google is your friend…
USB 1/2 are half duplex using one twisted differential pair and 3 is full duplex using two twisted differential pairs. The signaling is digital using differential drivers and receivers.
There are a number of parameters that are measured to confirm a cable meets requirements but differential impedance, skew and insertion loss are the most important for proper operation especially for USB 3.0.
The differential impedance of the cable assembly (twisted pairs + connector) is supposed to be tightly controlled. The certification mask for the connector to cable interface and the connector to connector interface loosens a bit. A differential TDR or Vector Network Analyzer with special SW is used) The time skew between the + and – wires of each pair must be tightly controlled. This is measured with special equipment. If the cable loss is too high due to crappy quality cable or too long a cable, you will have problems. If the skew between the + or – wires of a pair is too high, you will have problems.
Building cables to meet all the requirements in the certification document and at the same time being cheap is nearly impossible. You can start out with good cable and connectors, but the fabrication time required to meet certification is too high to meet cost. In general companies make “gold standard cables” to be submitted for certification.
This is the reason why USB cables make huge difference. 95% of them are pure rubbish, and will make the sound reproduction system sound the same.
I found that the termination is very important, to preserve the signal transfer consistency between the end –connector pins and the twisted pair cable. It all makes huge difference sound-wise. It is easily noticeable.
Even a single twisted pair, out of 4 found in a cat6e shielded Ethernet cable, will be close to 90 ohms impedance if shielding & geometry is preserved, and will sound vastly superior to cheap rubbish USB cables half of fellas here are trying to make us believe are good for audio reproduction.
With the introduction of digital audio, we are starting to see a large number of electronic experts who are trying to justify their beliefs by saying it is only ones and zeros; it can’t possibly make any difference what type of USB cable you use. And then I give them cat6e Ethernet cable I explained above, that costs $15 with a gold plated USB A and B connecters at cable ends. The first comment is: gold plated won’t make any difference, it is only ones and zeros (you idiot), to which I reply: do you believe that the fast changing stream of zeros and ones is not affected by a build-up of contact resistance due to oxidation? Anyhow, the real jaw-draping moment happens when we replace the “perfect for audio printer USB cable” with cat6e. There’s that deadening silence when they start to question everything they’ve been saying up until that moment. Half of them (many are university lecturers teaching the youngsters electronics at the degree and the post-graduate levels), still say: “this can’t be - this is impossible” …?????? The other half just keeps quiet while the brain is processing what just happened.
There’s no hope for that first half, their egos will stand in the way of what their sense of hearing is telling them to be vastly better.
To finish them off, I then replace the USB DAC power cable (of course, it is a “perfect for audio printer mains cable”) with a solid core copper cable, properly terminated. “It is just a 240V AC mains power – it won’t make any difference”… and the jaw-dropping moment repeats itself.
Nick
This is the reason why USB cables make huge difference. 95% of them are pure rubbish, and will make the sound reproduction system sound the same.... Anyhow, the real jaw-draping moment happens when we replace the “perfect for audio printer USB cable” with cat6e. There’s that deadening silence when they start to question everything they’ve been saying up until that moment. Half of them (many are university lecturers teaching the youngsters electronics at the degree and the post-graduate levels), still say: “this can’t be - this is impossible” …?????? The other half just keeps quiet while the brain is processing what just happened. There’s no hope for that first half, their egos will stand in the way of what their sense of hearing is telling them to be vastly better...
Hi ! thanks for the interesting comment.
I have one trivial question ... how can you replace a usb cable with a cat6e ? i have missed something ? i mean ... they are different standards
Are you using an adapter ?
To finish them off, I then replace the USB DAC power cable (of course, it is a “perfect for audio printer mains cable”) with a solid core copper cable, properly terminated. “It is just a 240V AC mains power – it won’t make any difference”… and the jaw-dropping moment repeats itself.
Nick
for this i have an explanation. In the end a power cord having a L, C and R can act as a filter and suppress some noise coming from the electrical grid.
Noise from the mains is for real. I have usually experienced better sound during the night and holidays and i have related this to less disturbs in the electrical grid.
Thanks again, gino
There is a certification for USB cables. If you use a certified cable and it meets the spec the bits will get through and its up to the receiver to deal with it. If you buy cheap ebay uncertified knock offs then it may not be to spec. But you won't get a darkening of the vocals or a veil in front of the music, you will get drop outs.This is the reason why USB cables make huge difference. 95% of them are pure rubbish, and will make the sound reproduction system sound the same.
I found that the termination is very important, to preserve the signal transfer consistency between the end –connector pins and the twisted pair cable. It all makes huge difference sound-wise. It is easily noticeable.
Even a single twisted pair, out of 4 found in a cat6e shielded Ethernet cable, will be close to 90 ohms impedance if shielding & geometry is preserved, and will sound vastly superior to cheap rubbish USB cables half of fellas here are trying to make us believe are good for audio reproduction.
would these be the same experts who can actually measure things and perform controlled listening tests to back up the theory?With the introduction of digital audio, we are starting to see a large number of electronic experts who are trying to justify their beliefs by saying it is only ones and zeros; it can’t possibly make any difference what type of USB cable you use.
Yeah cos sighted listening is well proven to do this.There’s no hope for that first half, their egos will stand in the way of what their sense of hearing is telling them to be vastly better.
Like SY has said several times, any data to back up your assertions?
There is a certification for USB cables. If you use a certified cable and it meets the spec the bits will get through and its up to the receiver to deal with it.
If you buy cheap ebay uncertified knock offs then it may not be to spec.
But you won't get a darkening of the vocals or a veil in front of the music, you will get drop outs ...
Hi and sorry to jump in. So if it works is fine ?
I mean, if i do not hear drop outs one is like another ? 🙄
Just to understand if the premium grade variety is for chicken 😉
Thanks a lot, gino
Last edited:
Two USB modes.
In async mode clock is generated in the DAC so as long as the bits get through its not the cables problem
In sync mode you are recovering clocking information from the incoming bit stream. There is a theoretical possibility of the horror of jitter but little measurement evidence to back this up. Receiver chipset designers are clever guys after all.
There are other potential gremlins but they are at the receiving DAC level and the cable has nothing to do with them
In async mode clock is generated in the DAC so as long as the bits get through its not the cables problem
In sync mode you are recovering clocking information from the incoming bit stream. There is a theoretical possibility of the horror of jitter but little measurement evidence to back this up. Receiver chipset designers are clever guys after all.
There are other potential gremlins but they are at the receiving DAC level and the cable has nothing to do with them
There are still usb dacs working in sync mode ??? 😱
I thought that recent usb dacs (since 4-5 years) were all working in async mode 😕
Am i wrong ?
Regards, gino
I thought that recent usb dacs (since 4-5 years) were all working in async mode 😕
Am i wrong ?
Regards, gino
One carries audio signal.
Wow! The insight is mind blowing! Sooo glad you cured us from our ignorance!
Jan
Last edited:
I like analogies.
The USB link has to transport a number. It depends on the application what the receiver does with the number.
So. I am the transmitter and want the guy at the receiving end to chalk the number 7 on a blackboard.
I yell 'seven!' . But I can't yell very loud and the receiver guy has not so very good ears (the analogy for a bad cable) yet the guy hears '... even..' . Using some simple error detection and correction in his head he concludes I yelled 'seven' and chalks '7' on the blackboard.
100% correct data transmission through a not so good connection.
That helps you to get it Boky? 😉
The task of a USB link is to deliver the same numbers at the far end as were stuffed in at the near end. That's ALL. It doesn't matter what the numbers represent. A Mahler symphony, the recipe for lycee pizza, or last year's tax return forms. It's all just numbers. Once the number has been delivered correctly, the USB's task is over.
Jan
The USB link has to transport a number. It depends on the application what the receiver does with the number.
So. I am the transmitter and want the guy at the receiving end to chalk the number 7 on a blackboard.
I yell 'seven!' . But I can't yell very loud and the receiver guy has not so very good ears (the analogy for a bad cable) yet the guy hears '... even..' . Using some simple error detection and correction in his head he concludes I yelled 'seven' and chalks '7' on the blackboard.
100% correct data transmission through a not so good connection.
That helps you to get it Boky? 😉
The task of a USB link is to deliver the same numbers at the far end as were stuffed in at the near end. That's ALL. It doesn't matter what the numbers represent. A Mahler symphony, the recipe for lycee pizza, or last year's tax return forms. It's all just numbers. Once the number has been delivered correctly, the USB's task is over.
Jan
Last edited:
I like analogies.
The USB link has to transport a number. It depends on the application what the receiver does with the number.
So. I am the transmitter and want the guy at the receiving end to chalk the number 7 on a blackboard.
I yell 'seven!' . But I can't yell very loud and the receiver guy has not so very good ears (the analogy for a bad cable) yet the guy hears '... even..' . Using some simple error detection and correction in his head he concludes I yelled 'seven' and chalks '7' on the blackboard.
100% correct data transmission through a not so good connection.
That helps you to get it Boky? 😉
Jan
Hi ! thanks a lot for the very useful and clear explanation.
On another hand, can we conclude that jitter is not an issue with a usb connection and async usb dacs ?
because there is a good quantity of usb anti-jitter devices on the market.
And also of usb galvanic isolators.
Are they all useless ? i am not an expert just and end user so i am very interested to understand if i am wasting resources.
Thanks a lot again
Kind regards, gino
There are still usb dacs working in sync mode ??? 😱
I thought that recent usb dacs (since 4-5 years) were all working in async mode 😕
Am i wrong ?
Regards, gino
Some of use things over 5 years old. I use a Class 1.0 USB to SPDIF converter and it works perfectly doing exactly what it should. no clicks, pops, dropouts or veils. Just bits to the DAC. Money saved over approved golden ear solution spent on a couple of box sets.
Hi ! thanks a lot for the very useful and clear explanation.
On another hand, can we conclude that jitter is not an issue with a usb connection and async usb dacs ?
because there is a good quantity of usb anti-jitter devices on the market.
And also of usb galvanic isolators.
Are they all useless ? i am not an expert just and end user so i am very interested to understand if i am wasting resources.
Thanks a lot again
Kind regards, gino
Most of them are poorly implemented and don't do what they claim! so yes, waste of money unless you like being persuaded that things sound better by spending money.
<snip>... On another hand, can we conclude that jitter is not an issue with a usb connection and async usb dacs ?
because there is a good quantity of usb anti-jitter devices on the market.
Yes it was a clear explanation but unfortunately your statement in bold indicates that you did not still grasp the implication of the analogy.... consider yourself still not understanding this - or at least you could not make logical conclusions of your newly acquired knowledge.
Is this so hard???
Its obvious that there are a lot of people thinking they understand clock structures and jitter but it seem like they who do are in minority after all.
Is there a standard pointer to some suitable document??
//
Some of use things over 5 years old.
I use a Class 1.0 USB to SPDIF converter and it works perfectly doing exactly what it should. no clicks, pops, dropouts or veils. Just bits to the DAC. Money saved over approved golden ear solution spent on a couple of box sets
Hi and thanks for the kind reply.
I see your point. Good old approach can be perfectly ok also by today standards.
Most of them are poorly implemented and don't do what they claim! so yes, waste of money unless you like being persuaded that things sound better by spending money
Let's say that i find them handy to inject some clean power whith usb headphone amp using usb power to work.
The usb bus power is not a reference for cleaness and strenght.
Only for that. Maybe these things have drawbacks but as long as i do not get clicks or drop outs using them they are fine. This i have learned now 😉
Thanks a lot again, gino
Yes it was a clear explanation but unfortunately your statement in bold indicates that you did not still grasp the implication of the analogy.... consider yourself still not understanding this - or at least you could not make logical conclusions of your newly acquired knowledge.
Is this so hard???
Its obvious that there are a lot of people thinking they understand clock structures and jitter but it seem like they who do are in minority after all.
Is there a standard pointer to some suitable document??
//
Hi and sorry i guess i do not understand.
But ... i think i have got what i really wanted to know. A clear evidence of something going wrong.
The rule i have learnt so far and that for me it is enough is that as long as i do not hear clicks or drop outs there is no problem at all.
This is very important for me.
And actually with a device i am testing now (usb extender on cat 6 cable) i indeed get clicks ... this means that it does not work properly.
What is really strange is that changing the usb dac for one much cheaper the clicks disappear 😕
However i will rely on my ear for clicks and drop outs. Very easy test.
Thanks a lot again.
Regards, gino
Hi ! thanks a lot for the very useful and clear explanation.
On another hand, can we conclude that jitter is not an issue with a usb connection and async usb dacs ?
because there is a good quantity of usb anti-jitter devices on the market.
And also of usb galvanic isolators.
Are they all useless ? i am not an expert just and end user so i am very interested to understand if i am wasting resources.
Thanks a lot again
Kind regards, gino
If you hear noise from USB and no other source, a galvanic isolator might be useful. I have never experienced this with several different computers and DACs I've used, but maybe, possibly, there's some combination of computer and DAC that's noisy (no one has shown any examples yet).
The anti-jitter devices are very useful in the treatment of neurosis. They don't cure the neurosis but they redirect it to the next non-problem which requires spending money.
If you hear noise from USB and no other source, a galvanic isolator might be useful. I have never experienced this with several different computers and DACs I've used, but maybe, possibly, there's some combination of computer and DAC that's noisy (no one has shown any examples yet).
The anti-jitter devices are very useful in the treatment of neurosis. They don't cure the neurosis but they redirect it to the next non-problem which requires spending money.
Hi and thanks a lot indeed for the always helpful advice.
I am pretty sure that most of my problems came from cheap and sub-standard usb cables. Some of them are quite loose when in place.
In general i prefer cables with locking mechanism ... rj45, bnc, xlr.
Maybe one day the industry will take notice at least for units of a certain level of quality. They tend to use rca everywhere.
However replacing the usb cable has worked nicely.
No more questions.
Thanks a lot again, gino
If a usb to spdif converter is made according the specified standards, it has a output transformer and galvanic isolation.
I spend an afternoon some time ago checking my collection of USB cabls after I noticed that one of my devices did not work with a specific cable, but did work with another cable.
Ended up cutting in half a handful of USB cables (my version of Widlarizing them 😉
Jan
Ended up cutting in half a handful of USB cables (my version of Widlarizing them 😉
Jan
- Status
- Not open for further replies.
- Home
- Source & Line
- Digital Line Level
- Is jitter an issue with usb signals ?