A USB Cable Test Designed to Satisfy Skeptics AND Believers—Feedback Welcome

[TLEDDY]

I wouldn't relate this to 'anti-vax' at all....more like flat earthers. Anti-vax actually has some merit too it, it's already been proven to create health issues in some people as well as the untrusted quick process and lack of manufacturer liability.

What you're speaking of is more like flat earthers where the only reason to believe such a thing is just because it's what they desire to believe.

Before polio vaccine was invented, I had Bulbar Polio, resulting in paralysis in my swallowing muscles and weakness in my left leg. I was hospitalized at Walter Reed Army hospital for two months. My Pediatric Ward had deaths every day; others were confined to the “iron lung” to stay alive on a separate ward.

The polio virus is still present in feces and sewers world wide, especially under developed countries.

My great fear is another epidemic of polio, absent vaccination.

Tillman

 

[Sal1950]

What would it take to end the cable debate? This is the question I keep thinking about as I read the cable discussions that inevitably devolve into religious arguments. Although individual hobbyists have conducted their own personal experiments and audio scientists have conducted peer-reviewed research, the current evidence still leaves the debate open. So, what kind of test would it take to satisfy both skeptics and believers?

I don't believe there could ever be a debate ending test.
Prove there is NO GOD, I doubt it.

 

[RexrothPigeon]

I have a friend with such an R2R DAC that requires signal cleaning before doing its job.

we can either respond to this information by thinking "well, that person better spend extra on super cables" or by thinking "well, that person should and buy a competent DAC." Either response to that friend is just fine. But for a general readership like that of this forum, and in service of a practical, general approach to sound accuracy, there's no contest which response is more useful to more people.

 

[SanojS]

we can either respond to this information by thinking "well, that person better spend extra on super cables" or by thinking "well, that person should and buy a competent DAC." Either response to that friend is just fine. But for a general readership like that of this forum, and in service of a practical, general approach to sound accuracy, there's no contest which response is more useful to more people.

He loves his DAC. He bought shitload expensive streamer with discrete power to come around the issue and isolate out the issues. Many people are like that, they have an affiliation for certain things that don't make sense to you. For him, a USB cable measurement might be vital. If you don't care about this, why are you discussing it?

 

[SanojS]

1 - Jitter is not a thing for USB. Data is clocked by the DACs cock - not by the source. Similarly therefore, no re-clocking issues. Even if there were, then jitter rejection and clock recovery in modern dacs is good enough to reduce timing distortion well below the level of audibility. (We don't have to worry about jitter anymore for Toslink or Coax connections either)

2 - Ground loop noise is not altered by a USB cable in any shape or form. While the cable shield will conduct the ground currents - that is regardless of the quality of the cable - all shields conduct ground currents - that is what they are for. Ground loop currents can create signal noise along an unbalanced analogue interconnect - but not along a digital connection. If you have ground noise then you need to eliminate it by breaking it (eg. use toslink) or use balanced analogue interconnect. Playing with USB cables will deliver precisely nothing.

Not all DACs have good jitter control, remember that many people are still using DACs from the 90s. And they don't want the new stuff. For them, this is a very interesting test case. Jitter IS a thing for USB audio. How can you claim that? I don't understand people who state things like that... it is a very common issue, unless you have a very new and state of the art DAC. A majority still don't have that. Maybe here on the forum, but in general no. Still a lot of people use DAC on their old integrated AVR or Yamahas from 20-30 years ago. For them, this can be a real issue!
You can also FOR SURE have jitter issues on toslink! For new equipment and good quality fiber over shorter distance probably not common. But A LOT of people have old AVR/old toslink fiber, old integrated amps.

 

[RexrothPigeon]

many people are still using DACs from the 90s.

I am not a young person, so I'm comfortable saying that neither are they, and while their DACs may be the same as the 90s, their hearing definitely isn't

 

[Keith_W]

Prove there is NO GOD

Without getting into an argument about religion, this statement is a classic attempt at shifting the burden of proof. The burden of proof rests on the person making the claim. It's like saying "prove that there is no difference between cables". It's not up to me to prove there is no difference, it's up to the person who is making the claim to prove that there is. Bertrand Russell gave an example called Russell's teapot.

 

[voodooless]

I have a friend with such an R2R DAC that requires signal cleaning before doing its job.

Great, that means that this is confirmed with measurements?

Even in the 90s, DACs had PLLs and would reject jitter. And cables do not add enough jitter to be audible in any way, shape, or form. A "better" cable won't fix a poorly designed product.

How can you claim that? I don't understand people who state things like that... it is a very common issue, unless you have a very new and state of the art DAC

It's so common that from all the DACs that @amirm reviewed, there were almost none with jitter issues, regardless of price.

 

[wwenze]

Not all DACs have good jitter control, remember that many people are still using DACs from the 90s.

USB Audio Class 1.0 was only created in 1998......

 

[Roland68]

He loves his DAC. He bought shitload expensive streamer with discrete power to come around the issue and isolate out the issues. Many people are like that, they have an affiliation for certain things that don't make sense to you. For him, a USB cable measurement might be vital. If you don't care about this, why are you discussing it?

Not all DACs have good jitter control, remember that many people are still using DACs from the 90s. And they don't want the new stuff. For them, this is a very interesting test case. Jitter IS a thing for USB audio. How can you claim that? I don't understand people who state things like that... it is a very common issue, unless you have a very new and state of the art DAC. A majority still don't have that. Maybe here on the forum, but in general no. Still a lot of people use DAC on their old integrated AVR or Yamahas from 20-30 years ago. For them, this can be a real issue!
You can also FOR SURE have jitter issues on toslink! For new equipment and good quality fiber over shorter distance probably not common. But A LOT of people have old AVR/old toslink fiber, old integrated amps.

May I ask which DAC that is?

I'm also still using a DAC from the 90s, a Cambridge Audio Dacmagic 1.

 

[somebodyelse]

Yes, cable doesn't do clocking/reclocking and I never said so, I said it can CAUSE ISSUES with reclocking in DAC stage, that affects the receiving end from properly reclock the signal. It can be because of significant noise pollution through the ground for example, or if jitter is severe enough that the DAC isn't able to completely recover the correct clocking sequence.
Jitter is the result of improper timing between packets and can be the result from impedance mismatches, sub-par shielding causing interference, and signal degradation.

Happy now?

Not really - it's more hand-waving with no specifics.

The USB standard defines the acceptable signal timing performance, and compliance tests to ensure compatibility - see for example https://testusb.com/HSEYE.htm. The problems you describe would mean the host, cable or device was not conforming to the standard - jitter would cause the rises and falls at each side of the eye to occur earlier and later, and if bad enough would spread into the red keep-out area. If you've got a cable that's out of spec then you should expect problems.

We also need to be specific about whether the device is using UAC synchronous, asynchronous or adaptive mode. The vast majority of hifi DACs are using asynchronous connections, so the audio clock is local in the device, not derived from the USB start of frame. That means timing errors on the USB bus don't affect the audio clock. If you're talking about synchronous or adaptive then we're back to whether the PLL in the DAC can lock within the allowable timing variations for start of field, and how well it performs. That's a DAC issue if everything's within spec.

It's not clear exactly what sort of reclocking you're talking about.

Ground noise shouldn't affect the USB data signalling as that's differential. It may affect the DAC if it's poorly implemented (it's something the designer should anticipate as an inherent part of USB, and design accordingly), but that's a system issue not a cable issue. The ground and/or shield resistance will change how much ground noise voltage any leakage currents appear as, but again that's something the designer has to deal with for standards-compliant cables.

 

[Sal1950]

Without getting into an argument about religion, this statement is a classic attempt at shifting the burden of proof. The burden of proof rests on the person making the claim. It's like saying "prove that there is no difference between cables". It's not up to me to prove there is no difference, it's up to the person who is making the claim to prove that there is. Bertrand Russell gave an example called Russell's teapot.

Yep, I know. I just threw that into the thread to show how hopeless it was to argue over.

 

[antcollinet]

Jitter IS a thing for USB audio. How can you claim that? I don't understand people who state things like that.

Because of the way asynchronous usb audio works. Data is requested from the source by the DAC, based on the DACS own clock. The data is then placed in a buffer inside the DAC, and clocked out of the buffer using the DAC's stable clock

Any timing issues from the USB interface are completely irrelevant, since only the DAC clock is used to time the data out of the buffer, into the actual conversion. No re-clocking is needed, no PLL, and jitter from the source or cable have no bearing.

Only if the DAC clock itself is unstable can there be any jitter. And this has nothing to do with the USB. And I don't think there has been any DAC tested here with a clock unstable enough to cause audible jitter.

If you are unable to "understand people who state things like that", the only reason I can think of is that you don't understand how the system works.

 

[solderdude]

Only true for asynchronic data transfer, not so for synchronous nor adaptive.
For synchronous there is a clock and a PLL and the DAC clock synchronizes to the USB signal which can vary (jitter).
Depending on the type, severity and frequency spectrum of the jitter most will get rejected but some may still be not rejected enough.
The audibility of the various types of jitter is still not entirely clear.

Some older DACs had issues but today even synchronous USB has excellent jitter rejection.
The receiver as well as the source USB signal quality as well as defective cables can cause issues with certain DACs (especially some older ones).

That said... a lot of 'inexplicable' subjective observations are often attributed to 'jitter' kind of as a scapegoat while not being the actual cause of the 'observations'.

Just like the famous 'dirty 5V' (which sometimes is a problem when the voltage is too low or the DAC is really crappy designed) or the 'noise on the ground' or 'noise on the +5V' which do not affect the data (differential) but can cause audible issues due to poor layout (usually of the digital/analog ground issues) and can become audible as 'unwanted noises' (the typical groundloop).

 

[ahofer]

Not all DACs have good jitter control, remember that many people are still using DACs from the 90s. And they don't want the new stuff. For them, this is a very interesting test case. Jitter IS a thing for USB audio. How can you claim that? I don't understand people who state things like that... it is a very common issue, unless you have a very new and state of the art DAC. A majority still don't have that. Maybe here on the forum, but in general no. Still a lot of people use DAC on their old integrated AVR or Yamahas from 20-30 years ago. For them, this can be a real issue!
You can also FOR SURE have jitter issues on toslink! For new equipment and good quality fiber over shorter distance probably not common. But A LOT of people have old AVR/old toslink fiber, old integrated amps.

Jitter is VERY RARELY a thing. (Be sure to click on the links that might, at first glance, seem to support your point - they do not).

DEMO / MUSINGS: Let's listen to some jitter simulations with sideband distortions...

A blog for audiophiles about more objective topics. Measurements of audio gear. Reasonable, realistic, no snakeoil assessment of sound, and equipment.

archimago.blogspot.com

You can find lots of other digital sound blind tests on Archimago, with large numbers of diverse responses. It lays a lot of claims about the sound of DACs and connectors completely to rest.

 

[antcollinet]

Only true for asynchronic data transfer, not so for synchronous nor adaptive.

Hence my stating "asynchronous" in every post I've made on the topic above.

And as I've also stated - the vast majority of recent dacs (say the last decade or so) are operating in asynchronous mode. The solution to USB jitter problems (if they exist, and audibly they probably don't) isn't a new USB cable.