Head-Fi.org › Forums › Equipment Forums › Sound Science › USB cable and Sound Quality
New Posts  All Forums:Forum Nav:

USB cable and Sound Quality - Page 23  

post #331 of 783
Quote:
Originally Posted by drez View Post

 

This is an interesting question though as it does throw into question a lot of the assumptions regarding how USB cables might affect jitter in USB audio.

I say it's YOU throwing in 'an interesting question' ..

 

Either the '0' and '1's are there .. Or they are not .

IF the 'cable' complies with standards and has no mechanical defects it will transfer all the 0 and 1's .

If not, the receiving end will know .

(There is a slight possibility of ground-loop issues in some cases, this could easily be audible)

 

It's not alchemy, it's computer-'science' .


Edited by AKG240mkII - 8/28/12 at 10:51am

Gear mentioned in this thread:

post #332 of 783
Quote:
Originally Posted by bigshot View Post

Wouldn't minute timing errors affect high frequencies where the waveform is all bunched up, than low frequencies where the waveform is five feet long?

 

No. The number of bits for a high frequency or low frequency are the same (1s and 0s) for any given segment of time. 

post #333 of 783

I bought the Transparent USB cable to cover all my bases. I never did a real comparison. It was an inexpensive tweak. I also like the styling and build quality. I love their stuff so I figured why not for $95.

post #334 of 783
Quote:
Originally Posted by BlackstoneJD View Post

I bought the Transparent USB cable to cover all my bases. I never did a real comparison. It was an inexpensive tweak. I also like the styling and build quality. I love their stuff so I figured why not for $95.
Not as much as some, but way too much for what it is supposed to do.
post #335 of 783
Quote:
Originally Posted by drez View Post

 

I'm not sure but I think HiFace describe the transfer mode they use as bulk mode, although I'm not sure how this applies specifically and it probably varies depending on the driver in question.  This is an interesting question though as it does throw into question a lot of the assumptions regarding how USB cables might affect jitter in USB audio.  I can say that my personal non-controlled experience with the battery modified HiFace I was using that USB cabling (especially length with very short cables eg <10cm) did still affect the sound for better or worse, and that was completely powered from battery, and presumably doesn't care much about the timing of incoming data as it uses batch mode with some sort of hardware buffer.  It would be interesting to find out how many samples are sent in each USB transfer packet, but I have my doubts that the driver designers will be willing to disclose this information.  Are there any open source USB audio driver projects??biggrin.gif.  Knowing what I know now though, maybe too short cabling may have made signal reflections worse but I guess it is hard to say without testing.

The USB transfer modes are not proprietary and can be downloaded through the USB forum web site. The drivers are chip specific and are usually provided by the chip vendor for free. 

 

 For cable, as long as the cable are compliant, they should work just fine. Bit error cause the audio to have a pop corn like sound. It sounds like a lot of static. The poor quality you hear on your cell is caused by bit error (the phone will try to compensate for it). If you hear a lot of static then you have a transmission issue. You will not lose bass or treble because of bit error.

post #336 of 783
Quote:
Originally Posted by AKG240mkII View Post

I say it's YOU throwing in 'an interesting question' ..

 

Either the '0' and '1's are there .. Or they are not .

IF the 'cable' complies with standards and has no mechanical defects it will transfer all the 0 and 1's .

If not, the receiving end will know .

(There is a slight possibility of ground-loop issues in some cases, this could easily be audible)

 

It's not alchemy, it's computer-'science' .

 

Welcome to Head-Fi - I see you have taken the obligatory 1's and 0's pamphlet to heart.  Now  that I have grasped this I have been able to fully resolve a theory of quantum gravity and at the same time solved world hunger.biggrin.gif  Seriously sorry just I have heard that argument about a million times and don't find it cute anymorefrown.gif

 

In fact what I was saying is that some of the assumptions about how timing variations from the computer or cable may be far from what is happening given what dvw was saying about the clock frequency of USB it may not be possible for USB to send individual samples over USB and is instead probably sending a certain number of samples at a time in bulk mode.  My guess is that asynchronous just makes it easier for the USB audio device to manage the buffer.

 

Most decent USB transports now include galvanic isolation, but otherwise if you are running a desktop PC you could just use the same earth for your DAC and the computer.  If you are running a laptop then galvanic isolation might be necessary as the laptop uses a floating ground.  I don't think this is directly related to most USB cable sound difference claims.

 

Under normal circumstances I don't think USB transports drop packets as long as they have well designed drivers and a large enough buffer on the computer side.  Most of what I have been discussing is trying to figure out what is causing some of the observable differences between computer hardware and software that I have and continue to observe derive from given that there is little scientific explanation beyond simply writing off these observations as invalid or flawed/unreliable.  I personally find it highly unlikely that suggestion and cognitive bias is responsible for repeated and independent observations of variations between hardware and software including cables, playback software etc.  Unfortunately philosophical and financial factors have generally thwarted attempts to make progress in establishing a scientific understanding of computer based music transports.

 

For USB cables I think the influence may be how little they can add noise and jitter to the digital signal pair, power and ground connections.  Why do I think this might affect audio quality - mostly because USB was not designed to handle real-time multimedia interfaces like Firewire, PCI etc.  This may be a tenuous argument but if you look at the Firewire and USB standards they are very different in both hardware and software.  USB audio now uses asynchronous transfer but I am not sure that this magically fixes the limitations of using USB for audio in the same way that buffers do not magically fix any timing variations that originate upstream no matter what the manufacturers claim.  

 

As to why software might make a difference the most convincing arguments I have heard are from the makers of Puremusic for Mac and JPlay for PC - they claim that by using different driver level changes they can achieve more consistent latency, and that this, even with asynchronous transports, can lead to better sound quality.  Who knows, maybe the latency is not directly having an influence but instead it is affecting electrical noise and voltage stability of the USB connection, nobody has really shown a causal link between any of these factors and sound quality.  From my own observations though these factors can be heard with most equipment quite easily.  If you cant hear a difference or don't believe me that's fine, maybe your gear has better jitter immunity or something but for me it is worthwhile to pursue these things as I do hear differences, and I would suggest that they are at least worth investigating if not investing inwink.gif

post #337 of 783
Welcome to Sound Science. Just saying you can hear it and coming up with a complicated explanation of what you think you might be hearing don't cut the mustard here.

Have you done controlled testing to verify what you think you hear?
How much noise and jitter? Have you measured it?
What is the threshold of audibility for this kind of noise and jitter?

And the bonus question... What does this noise and jitter sound like?
Edited by bigshot - 8/28/12 at 9:54pm
post #338 of 783

You can read a great deal from industry experts who have done the measurements and tests here:

 

http://www.head-fi.org/t/493152/low-jitter-usb-dan-lavry-michael-goodman-adaptive-asynchronous

 

Short answer is, USB Audio is a streaming protocol where timing (and thus waveform quality) matters a great deal, unlike the digital transmissions inside a computer.  However newer electronics that buffer the stream (are asynchronous) or otherwise reduce the jitter significantly before conversion make USB quality mostly a non-issue.

 

There is one member here who has the $100k of equipment necessary to test down the femtosecond level of jitter, as well as other things whom, if asked kindly, might consent to doing some measurements, so that instead of arguing based on beliefs, you can argue over your beliefs in the relevance of some measurements instead. tongue.gif

post #339 of 783

Oh yeah, latency.

I forgot about that one redface.gif

post #340 of 783
Quote:
Originally Posted by bigshot View Post

Welcome to Sound Science. Just saying you can hear it and coming up with a complicated explanation of what you think you might be hearing don't cut the mustard here.
Have you done controlled testing to verify what you think you hear?
How much noise and jitter? Have you measured it?
What is the threshold of audibility for this kind of noise and jitter?
And the bonus question... What does this noise and jitter sound like?

 

Haha touchebiggrin.gif

 

Controlled testing with USB cabling would require a second person willing to humor my interests which is not something I can arrange easily at present.  I may be able to do so in the future but this would be rather a kind (or unkind) gesture toward sound science.  Contrary to popular belief I am not here to prove anything, and doing so would in my opinion be a disservice as some people with some systems simply do not hear some of these changes (software and differences in transports).

I am not making any specific claims about jitter.  playback software developers such as XXHighEnd and CPlay have attempted to measure the jitter performance of their respective projects but given the history of this thread I would not attempt to offer this as evidence of better performance.  Again it would be a theory to explain what I claim to hear between different softwares, and again these variations are easy for anyone to verify of their own accord and I would encourage them to do so.

I have no clue as to the specific threshold of audibility of noise and jitter in an SPDIF transport, if one were to measure the level of electrical noise on the SPDIF output of the Audiophilleo 2 and compare this to the new battery powered version I would offer this as a possible demonstration.  Again I have not blind tested the difference between these (I have done a sighted comparison switching between the two at a recent meet but did not have time to compare blind) but if anyone is interested I would encourage them to compare between the two at their own leisure.

I do not know what jitter sounds like, and further I am not sure what aspects of the differences I am hearing is attributed to jitter or not.  This kind of study is beyond the resources and knowledge I have at my disposal.

 

If I were to return to a conversation we had a while ago - I do not consider my casual observations to be evidence upon which other people should make decisions, but for my own decision making I consider them to be adequate as even if the differences are imagined, they are real to me.

post #341 of 783
Quote:
Originally Posted by Currawong View Post

You can read a great deal from industry experts who have done the measurements and tests here:

 

http://www.head-fi.org/t/493152/low-jitter-usb-dan-lavry-michael-goodman-adaptive-asynchronous

 

Short answer is, USB Audio is a streaming protocol where timing (and thus waveform quality) matters a great deal, unlike the digital transmissions inside a computer.  However newer electronics that buffer the stream (are asynchronous) or otherwise reduce the jitter significantly before conversion make USB quality mostly a non-issue.

 

It is also ABUNDANTLY clear, that the difference of a USB cable cannot affect just the bass, or just the treble energy, or any such claims.

 

And as regards jitter or latency and such, as far as I know, all streaming USB protocols (adaptive, sync, or async) have electronics in place which deal with jitter and other timing issues *before* the D/A Conversion - the only place that it would even possibly matter. 


Edited by liamstrain - 8/28/12 at 11:23pm
post #342 of 783
Quote:
Originally Posted by liamstrain View Post

 

It is also ABUNDANTLY clear, that the difference of a USB cable cannot affect just the bass, or just the treble energy, or any such claims.

 

And as regards jitter or latency and such, as far as I know, all streaming USB protocols (adaptive, sync, or async) have electronics in place which deal with jitter and other timing issues *before* the D/A Conversion - the only place that it would even possibly matter. 

 

That is if we are assuming the cable can only have an effect through jitter, which is probably true if the SPDIF output is galvanically isolated and run from an independant power supply.

 

In my casual, sighted experience I have heard a USB controller contribute artifical bass bloom and heft, as well as changes is processor scheduling, different HiFace drivers could all effect the degree of bass and lower midrange bloom, of course none of these are USB cables so I have probably digressed but these are easier elements to isolate as they have definite functions that can be identified.

 

Not that it matters really but I think much of what is considered to be the sound of jitter is rubbish and being mistaken with other influences (maybe electrical noise, or just even just more accurate reproduction etc.)  This interview with Igor Levin tends to suggest that the relationship between jitter and sound signature is not so straightforward:

 

post #343 of 783
Quote:
Originally Posted by liamstrain View Post

Quote:
Originally Posted by Currawong View Post

You can read a great deal from industry experts who have done the measurements and tests here:

 

http://www.head-fi.org/t/493152/low-jitter-usb-dan-lavry-michael-goodman-adaptive-asynchronous

 

Short answer is, USB Audio is a streaming protocol where timing (and thus waveform quality) matters a great deal, unlike the digital transmissions inside a computer.  However newer electronics that buffer the stream (are asynchronous) or otherwise reduce the jitter significantly before conversion make USB quality mostly a non-issue.

 

It is also ABUNDANTLY clear, that the difference of a USB cable cannot affect just the bass, or just the treble energy, or any such claims.

 

And as regards jitter or latency and such, as far as I know, all streaming USB protocols (adaptive, sync, or async) have electronics in place which deal with jitter and other timing issues *before* the D/A Conversion - the only place that it would even possibly matter. 

 

What is lacking here in these discussions are specifics. I've seen this posted, in effect, numerous times, but no discussion or specifics about individual DACs and their capabilities. I also posted those links so that people who are interested in genuinely learning, not just arguing, might do some research. Beyond that, I'm not making any specific argument, just trying to direct the discussion to something beyond the regular arguments which don't benefit anyone.smile.gif

 

As I asked, is anyone interested in some actual measurements and experiments or only interested in arguing what they believe is correct?

post #344 of 783
Quote:
Originally Posted by Currawong View Post

As I asked, is anyone interested in some actual measurements and experiments or only interested in arguing what they believe is correct?

 

I would be interested to see actual measurements. Both timing issues/jitter and the usual run of frequency response comparisons would be interesting to see. 

post #345 of 783
Lots of specifics in the first post of this thread....

http://www.head-fi.org/t/486598/testing-audiophile-claims-and-myths

This really is the most useful post in Sound Science. It really should be pinned at the top of the forum. Maybe you could do that for us, Currawong.
New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: Sound Science
This thread is locked  

Gear mentioned in this thread:

Head-Fi.org › Forums › Equipment Forums › Sound Science › USB cable and Sound Quality