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Don't get why "Audiophile" USB Cable would improve sound quality - Page 44  

post #646 of 835


 

Quote:
Originally Posted by Prog Rock Man View Post

The evidence is certainly waited in favour of the argument that USB cables do not influence sound quality. There is only speculation as to how a USB cable could affect sound quality, which in a science forum is not good enough.



Hi Ian

 

There was a long thread in diyaudio by Joseph K, complete with measurements and scope pics, about the Hiface and the use of attenuators to reduce the reflections in the coax cable (which affected the sound).  One would think that since a digital signal is a digital signal, there would also be reflections in a usb cable.

 

Eric

 

Edit:  Even Jocko Homo from diyHIFI.org posted in one of the jkeny threads about the use of attenuators to clean up the digital signal in coaxial cables.


Edited by upstateguy - 8/2/11 at 7:42pm
post #647 of 835

Reflections exist, but where is the evidence of audibility?

post #648 of 835
Quote:
Originally Posted by Willakan View Post

Reflections exist, but where is the evidence of audibility?



Fortunately for everyone involved except the boutique cable manufacturers, nowhere.  There do need to be more professionally-done measurements done on this though...I wonder if nwavguy would be up to the job.

post #649 of 835
Quote:
Originally Posted by leeperry View Post


of course not, more like a clearer sound/soundstage...as in less jitter/THD.


Can you prove that?

 

post #650 of 835
maaan, I couldn't resist, so I emailed usb.org biggrin.gif
post #651 of 835

Originally Posted by Prog Rock Man View Post

Can you prove that?


Once you will have found and bought me the equipment to measure USB jitter, shure thang buddy!

post #652 of 835
Quote:
Originally Posted by leeperry View Post


Once you will have found and bought me the equipment to measure USB jitter, shure thang buddy!


don't they use THD+N and IMD as proxies for that?
post #653 of 835
Quote:
Originally Posted by Willakan View Post

Reflections exist, but where is the evidence of audibility?


Check out the diyaudio and diyHIFI threads for the scope shots.  The oscilloscope shots show that the hash is in the audio spectrum and that attenuators help clean it up.  I'm not an engineer, but I think they called it "padding" the line.

 

Check it out.

 

post #654 of 835
Quote:
Originally Posted by upstateguy View Post




Check out the diyaudio and diyHIFI threads for the scope shots.  The oscilloscope shots show that the hash is in the audio spectrum and that attenuators help clean it up.  I'm not an engineer, but I think they called it "padding" the line.

 

Check it out.

 



Fine, but but still does not mean it is audible, for that you need controlled listening tests

 

post #655 of 835

Bob Adams (Analog devices)   the youngest ever AES Fellow did a very good paper on jitter you can find a version of it in the back issues of The Audio Critic,

 

http://www.theaudiocritic.com/back_issues/The_Audio_Critic_21_r.pdf

 

he concluded that measuring jitter at the clock was almost always actually unnecessary as you can see it downstream in THD and IMD and if you read stereophile's measurements you will see that no device that has really bad jitter ever has good THD or IMD

Quote:
Originally Posted by svyr View Post



don't they use THD+N and IMD as proxies for that?


 

post #656 of 835

You can read coax cables reviews that claim different jitter measurements depending on which direction the cable was connected...why not USB again? Neither of those 2 protocols use ECC.

 


Edited by leeperry - 8/3/11 at 10:16am
post #657 of 835

Ironic, you finally get them to use measurements in reviews and they promptly go too far the other way and decide that if they can measure a difference, there has to be an audible difference.

EDIT: Also, the letters section of the Audio Inquirer provides conclusive proof that Mr.Fremer is a rather unpleasant person.


Edited by Willakan - 8/3/11 at 10:51am
post #658 of 835

 

Quote:
Originally Posted by nick_charles View Post

Bob Adams (Analog devices)   the youngest ever AES Fellow did a very good paper on jitter you can find a version of it in the back issues of The Audio Critic,

 

http://www.theaudiocritic.com/back_issues/The_Audio_Critic_21_r.pdf

 

he concluded that measuring jitter at the clock was almost always actually unnecessary as you can see it downstream in THD and IMD and if you read stereophile's measurements you will see that no device that has really bad jitter ever has good THD or IMD

 


 

Thanks for the article, it's indeed very interesting and clearly written. This goes right to my collection  wink.gif

 

It should be said however that some bits (not many) are kind of outdated; jitter today is most commonly measured by reviewers through the analog output and not by sticking an oscilloscope on the internal clock output pin.Jtest and all that. You still need fairly good equipment for that FFT analysis though. Prism and AP products don't come cheap...

post #659 of 835
Quote:
Originally Posted by 00940 View Post

You still need fairly good equipment for that FFT analysis though. Prism and AP products don't come cheap...


A while back I was following a jitter test thread on the UK discussion forum HDD audio. A chap posted (added) jitter samples ranging from 0 to 100ns. I ran these through Audacity and was able to correctly place them in ascending order of jitter magnitude just by doing a spectrum analysis and plugging the results into Excel
 

http://hddaudio.net/viewtopic.php?pid=775#p775

 

 

post #660 of 835

ok, but you already had the digitized samples. The ADC job is the hardest part, especially if we're trying to hunt small differences.

 

This said, no internet for me in the next days. I'll be back on the 23rd, hopefully with the copy of Paul Miller's USB cables measurements on hand.

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