Gbjerke
1000+ Head-Fier
- Joined
- Feb 5, 2009
- Posts
- 1,005
- Likes
- 10
Well if you have to train your ears to hear jitter, why would you do so? Just to spend money on removing it afterwards?
Originally Posted by Gbjerke /img/forum/go_quote.gif Well if you have to train your ears to hear jitter, why would you do so? |
Originally Posted by jcx /img/forum/go_quote.gif I believe he lost track of the context - 250 nS jitter is only ~1% of the 44.1 sample time - which is where this jitter # applies - not at SPDIF bit edges the only limit on digital domain jitter is that all the bits arrive in sequence and can be correctly assembled into the original value for the DAC every ~22uS further, jitter spectrum is important to understanding effects - 250 nS rms jitter with a 20KHz bandwidth limit will not corrupt > 1 MHz self clocked serial data |
Originally Posted by Dan Lavry /img/forum/go_quote.gif Well, something is way off here. You can find credible double blind listening tests where people could hear far bellow 1 nsec jitter. There is some good material out there, and I would start by looking at papers by Hawksford and Jullian Dunn. Don't you think that tt is remarkable to have such a huge differences in findings? Regards Dan Lavry |
Originally Posted by oldson /img/forum/go_quote.gif "Nobody is disputing the objective damaging effects of jitter , the big question is how bad does it have to be before we can actually hear it. " thats what i looked on this thread for. wished i hadn't now. all this is waaay above my head! |
Originally Posted by nick_charles /img/forum/go_quote.gif ...Nobody is disputing the objective damaging effects of jitter , the big question is how bad does it have to be before we can actually hear it. |
Originally Posted by Dan Lavry /img/forum/go_quote.gif I need to spend less time on the web, but given that you have been looking for a “jitter number” for a long time, let me suggest again to review Hawksford paper, and also Adams paper. http://www.essex.ac.uk/csee/research...e%20flawed.pdf I do not have a link for Adams paper but I believe you can find it. |
There is much to be read in that articles. Much of what Hawksford and Dunn did and talked about does have to do with keeping the jitter "below the threshold of audibility", not some made up figures but pretty well known levels for what real people can hear. As always, follow the references at the end of the paper… |
And I also highly recommend reading “Clock Jitter, DA Converters, and Sample –Rate Conversion” by Robert Adams published at the Audio Critic (or better yet, for any AES members, look for print # 3712). Bob Adams is an exceptionally brilliant engineer, highly respected by the engineering community! |
If nothing else, you may gain some understanding WHY there is no single number for jitter audibility. In Adams paper, he explains why a 1 bit 64fs (such as DSD) is vastly more susceptible to jitter then say a multi-bit sigma delta with a switched cap output stage. You will see that a resistor based R-2R DA has a different sensitivity to jitter… Add to that the facts that the type of jitter plays a role, and the frequency content for each type also plays a role. You can not have a meaningful single number for jitter audibility. There are too many variables, from jitter type and content to circuit architecture. In my view, the folks that do come up with papers, listening tests or comments ending with a single universal jitter number, are in fact showing much lack of depth regarding the subject of jitter. Regards Dan Lavry |
Originally Posted by b0dhi Incorrect. The correct conclusion is that it isn't detectable by conscious comparison by untrained listeners. "Audibility" is a seperate issue. Also, they had a mouse interface. They don't mention any keyboard control, which is strange considering how important it is to be able to perform the test with eyes closed. They also used a 100ms crossfade when the user wanted to switch samples. Also, the test only addresses frequency or amplitude domain effects of jitter. Time domain effects are not explored with their digital simulation method. The utility of this study is limited. |
Originally Posted by ert FTA "A total of 23 audio professionals or semi-professionals participated as the listeners. They were audio engineers, audio critics, sound engineers, and musicians." What is your definition of "untrained listener"? Also, I'm not sure that your distinction between "audibility" and "detectable" has any practical implication. An interesting study. They seem to discuss some more details of the simulation wrt actual observed hardware jitter in other papers. |
Originally Posted by AdamWysokinski Oh, is it? How can you determine sonic qualities of something that is not detectable by the hearing system? |
Originally Posted by nick_charles There are several different types of jitter, random jitter as in the paper you cite is indeed far less audible, Benjamin and Gannon used correlated jitter in their 1998 study and found the thresholds to be from about 20ns in music but getting as high as 300ns in some cases. Correlated jitter creates distortion sidebands while random jitter raises the noise floor. |
Originally Posted by leeperry well, I said "IMO"...I don't quite have the same kind of equipment the XXhighend coder has to measure jitter...I merely use my two ears to judge on that. |
Originally Posted by b0dhi If the test depends on conscious comparison and detection, it is a skill. It is therefore required to train the listeners if the result is to be extrapolated as "audibility" and not just conscious comparative detection skill. Audio-pros, musicians and audiophiles are not people trained in detecting jitter-caused distortion. Being slightly more likely to be able to do so than the general population due to one's profession/hobby is hardly "trained". |
Originally Posted by Dan Lavry Well, something is way off here. You can find credible double blind listening tests where people could hear far bellow 1 nsec jitter. There is some good material out there, and I would start by looking at papers by Hawksford and Jullian Dunn. Don't you think that tt is remarkable to have such a huge differences in findings? |
Originally Posted by punkaroo /img/forum/go_quote.gif Maybe my ears need a cleaning, but I've done a listening test using an iBasso D10, and hooked it up via USB and optical. I could not tell a difference in SQ using either or. I was shocked to say the least. I was really expecting optical to be on top, but nope! |
Originally Posted by SB /img/forum/go_quote.gif 20ns is still 20,000ps which is much higher then the current jitter measurements. |
Originally Posted by nick_charles /img/forum/go_quote.gif There is one device that gets to over 11ns. I guess we cannot say jitter is definitively always inaudible without more testing but all the controlled listening tests with whatever methodological issues they may have to date do point in the same direction... i.e the don't worry about it direction. |
Originally Posted by SB /img/forum/go_quote.gif What component is that? |
Originally Posted by nick_charles /img/forum/go_quote.gif The McIntosh Music Server. |