Swenson mentions two ways of using USB for audio. He doesn't seem to mention cable quality as an issue for either. This is as expected, because his article is about ground bounce which is an equipment/chip issue not a cable issue.
The only contribution his article makes is to confirm what we all already knew: that signal timing can sometimes matter too. When data alone is being transferred then timing doesn't matter. He says this by talking about local reclocking for async USB.
The only contribution his article makes is to confirm what we all already knew: that signal timing can sometimes matter too. When data alone is being transferred then timing doesn't matter. He says this by talking about local reclocking for async USB.
Jitter is the slight difference in timing of a BITs arriving at the receiver, it is not a separate entity it is a known problem with digital signal transmission, signal timing issues in the transmission of the BITS, hence its all about transmitting the bits, within the requirements of the digital interface, be it USB, SPDIF, DDR memory interface, gigabit Ethernet etc etc all have there requirements and you ENGINEER, simulate test your design to work within these requirements.
"Jitter is the slight difference in timing of a BITs arriving at the receiver," <- and this is the reason why buffers were invented - solved problem.
Rich
Rich
Please correct me if my reasoning is wrong.
Let take the case of USB data transmission
bits stream => USB host A => cable => USB host B => stream
in USB host A the bits from stream are packed with a checksum
the bits that are traveling thru cable are bot the actual stream bits but the packet bits
in USB host be the packets are transformed again in a stream
For USB Data transfer: if the CRC fails host B signals host A to retransmit the packet until it is received in proper condition (CRC matches) => the host B stream will be 100% accurate
For Audio USB async data tranfer host B does not request the packet retransmission but all above are the same, therefore is a packet is not received with the correct CRC it will be discarded and the result of DAC processing will be a pop. Or to go back some posts, if you transmit text characters thru this type of connection and you have faulty cable as a result you will have
missing characters but in no case more characters nor bold or italics.
I cannot see no mechanism that occurs in USB cable that can change the PACKETS (and consequentially the CRC check sums of packets) that run thru the cable and result in a different data stream in host B.
I believe that the differences that some people are perceiving between different cables are because of faulty implementations in hardware (host A , host B both)
So far, no-one has demonstrated that they can actually hear a difference, so speculation about potential causes is moot.
When I first got a USB DAC I just had to get an upgrade USB cable.
Well I did leave the printer without a cable and the missis was not too impressed, so to smooth the fur I splashed the cash on a fancy one with a braid type outer and gold plated plugs. It's made by well respected hi end cable manufacturer - Technica 😉
My buying criteria were crucial, I noticed it while being dragged round Tesco supermarket the next day 😀
There is an obvious difference between it and the printer cable though, the printer one is grey, this one is black. Other than that though, all it did was smooth some fur.
Well I did leave the printer without a cable and the missis was not too impressed, so to smooth the fur I splashed the cash on a fancy one with a braid type outer and gold plated plugs. It's made by well respected hi end cable manufacturer - Technica 😉
My buying criteria were crucial, I noticed it while being dragged round Tesco supermarket the next day 😀
There is an obvious difference between it and the printer cable though, the printer one is grey, this one is black. Other than that though, all it did was smooth some fur.
Are you unable to engage in discussion without resorting to personal insults? Actually maybe I am insane, you have already answered that question. Seriously though, why does the internet disable peoples' personal standards of etiquette? Is it because they are anonymous?
Swenson discusses the ground bounce induced by the switching of the input receiver on a USB input. Given that many USB receivers are powered by the computer via the USB cable, why would one ignore the impedance of the ground wire linking the computer's ground to the ground plane of the DAC?
Last edited:
This is from the second article under the heading USB input:
"Next is edge jitter, this is traditional jitter of the individual edges on the bus. As with everything else I have been talking about, jitter on the input can cause noise in the chip and on the ground plane that is related to the spectrum of the jitter. This is where things like different cables can have an effect on what is happening."
nonsense, he used the word cable, so you have focused on it. also what makes you think the impedance of the ground wire has been ignored? what makes you think there are not other ways to handle ground bounce? what makes you think hes recommending or saying that the cable is the solution? what makes you think hes not just making presumptions? because it sure sounds like he is to me, given his choice of words. what makes you think making the ground wire bigger would actually be a solution?
hes spitballing IMO, these things also do not cause effects that are invisible to normal measurement techniques and there are already ways to deal with them anyway if you believe it to be an area of real concern.
isolated fifo buffer, local reclocking, proper decoupling… done
as mentioned already here and i've used similar phrasing elsewhere, donning a tinfoil hat and trying different USB cables that somebody else made, randomly like an aerial; as a way to deal with what is essentially a plain vanilla grounding and power supply decoupling issue; is a really strange way to approach a solution
hes spitballing IMO, these things also do not cause effects that are invisible to normal measurement techniques and there are already ways to deal with them anyway if you believe it to be an area of real concern.
isolated fifo buffer, local reclocking, proper decoupling… done
as mentioned already here and i've used similar phrasing elsewhere, donning a tinfoil hat and trying different USB cables that somebody else made, randomly like an aerial; as a way to deal with what is essentially a plain vanilla grounding and power supply decoupling issue; is a really strange way to approach a solution
Last edited:
Oh come on. It was a rather friendly question to an outrageous claim. I was expecting you to reply why you aren't insane, obviously.
Where?
Again, it was not intended as an insult, it was only meant to emphasize that your claim was outrageous, and thereby encouraging you to explain.
If the power source is important in audio, and if audio gravely degrades from a bad power source, and if USB DACs should have a separate power supply, then clearly, in that case, we're talking about the issue of proper power supplies, not USB-cables.
So, for the sake of clarity, and to remove additional variables, lets remain in the topic of transmitting audio over USB-cables.
Anyone read that article?
Marlene's Musings: Vodoo continued: my final Statement on USB cables
It's the last one from a series with final conclusion.
He eared differences, he tried to measure, he found differences in measurements but later discovered that his measurements where faulty.
After fixing his mesurements he found no differences at measurements but still recognize differences with ABX via Foobar (!)
Interesting... it seem we need better measurements, after all. 😉
Marlene's Musings: Vodoo continued: my final Statement on USB cables
It's the last one from a series with final conclusion.
He eared differences, he tried to measure, he found differences in measurements but later discovered that his measurements where faulty.
After fixing his mesurements he found no differences at measurements but still recognize differences with ABX via Foobar (!)
Interesting... it seem we need better measurements, after all. 😉
Eh? You make an awful lot of presumptions.I don't think he has ignored impedance of the ground wire...I didn't make any judgements on his claims other than the fact they offer a plausible alternative to the "bits are bits" argument when dealing with the connection of two imperfect components. Where did I say or even imply that he said cable is a solution? Please read before posting.
In fact I don't discount the possibility that ground bounce can be dealt with in a well designed component;one could galvanically isolate the USB interface for a start. However where do you get the notion that this thread is "can USB cable make a difference in sound where the DAC is perfect"? People report that in some real world systems USB cables make a difference; given the variability in DAC design actually out there, I think this is feasible.
hes spitballing IMO, these things also do not cause effects that are invisible to normal measurement techniques and there are already ways to deal with them anyway if you believe it to be an area of real concern.
Agreed a good solution but...so?
Now I want you to quote where I advocated ANY solution at all.
Last edited:
I just skimmed the article and I do not know exact operation of Foobar ABX components. I am wondering how ABX with two wavs can test two cables.
He acquired the output of his USB soundcard (the one branched with the USB cables under test) with another USBsoundcard branched to a laptop.
Well, then I am afraid there could be lots of other factors at play. The most likely of them being a bit different recording gain setup. A tiny difference in volume would make the two recordings safely distinguishable.
IMO the only credible blind test is physical switching the actual cables.
You probably have missed something... the setup was identical and fixed in both hw and sw, the only change was the USB cable to the 'output' soundcard...how can you have different gain setup if you don't touch nothing but the USB cable?
Why debate it? Marlene can just post the files that were used.
Details on the test setup (block diagrams, equipment used, etc.) would be useful.
Details on the test setup (block diagrams, equipment used, etc.) would be useful.
- Status
- Not open for further replies.