 
|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
|
|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
76.25.70.1
In Reply to: RE: Jitter posted by Tubers on June 01, 2012 at 01:42:26
- - - If you cannot measure it, how do you know that you've reduced it, and how would you know if it was jitter in the first place that was causing your music to sound less than ideal?
Follow Ups:
IME there are no definitive ways to characterize jitter, becquse it has both qnd amplitude and spectrum component. The entire jitter spectrum must be examined, and even then the correlation to SQ has not been established.
So what you are saying is there are no clear definitions of what "jitter" actually is. Apparently jitter is a highly complex issue, or set of issues. One needs to examine all the facets of jitter, but even if one does that, there is no established correlation between jitter and sound quality.Wait, what?
All these audiophile vaporings and hyperventilating over jitter and no one has established a correlation between it and sound quality? Up above you ascribe all sorts of ills to jitter, but apparently none of them have been established as correlating to jitter? If there is no established correlation then how do you know jitter is causing the ills you complain of?
Edits: 06/04/12
As you know this Jitter Monster is as elusive as Big Foot.Nobody can get a good conclusive image of the Beast so they claim every turd in the forest belongs to it.
Dynobots Audio
Music is the Bridge between Heaven and Earth - 音楽は天国と地球のかけ橋
Edits: 06/05/12
I built a very inexpensive PLL circuit with the same high quality VCXO I used in my DAC. The input is attached to the clock to be measured, and the correction signal to the VCXO is bandpass filtered and then amplified, and I use the math and averaging functions on my storage scope for display. It's very sensitive, but not calibrated. I just use it as a "sniffer" type device and for comparison measurements. My main priority was getting visibility on very low amounts of data-correlated jitter, so I use it with a test CD, usually something with a worst case type signal for PCM induced jitter, such as the low level -90dB sine wave on most discs. This is the same type of method Stereophile and others used in the early days before switching to the analog sideband method. I believe there was even a construction article on a calibrated version in one of the DIY magazines way back then in the mid 90s. They all use the same general topology of extracting the correction signal, which will be mostly the jitter on the clock being measured.
Have you been able to 'see' the differences in jitter between say two different DACs under test? Were you able to make any correlation in the amount of jitter vs audio quality? How much jitter is necessary to definitively hear a difference?
I wonder if there's a way to deliberately increase or decrease jitter in real time while listening for changes in audio quality.
"I wonder if there's a way to deliberately increase or decrease jitter in real time while listening for changes in audio quality."
Now you're talking! Especially on the increase end of the knob...
I don't know if data correlated jitter is especially audible or merely a common problem. I need to re-read Dunn's paper, it's been many years. But as an approach to understanding systems, making things worse is more often than not an easier way to get a handle on what's going on than making them better. And it's a lot more accessible to us hobbyists since the only piece of exotic test equipment we need is already mounted to our necks.
Perhaps the sweetest thing about making things worse is that there is virtually no upper limit while at the other end we can only asymptotically approach perfection. Let's do it, let's make our stereos sound worse this very day!
And learn something...
Regards, Rick
..How do I deliberately and continuously increase jitter in real time while listening for changes? I like your idea of a 'jitter knob'. ;-)
So ya want MORE jitter do ya? Yea! How much can you take?
I suppose you could modulate the feed from the PLL to the oscillator, you could even filter it with the inverse of the PLL Fn to give you a direct dF/V even with the PLL fighting you at LF.
Might be fun to rig up a devilish digital dirt road. A cable that can slew rate limit the signal and run it through a comparator whose threshold you wily wiggle. The D^3 R, invented by Rick, not Al Gore...
Rick
So don't leave us hanging! Tell us more about this gadget of yours! How well does it work? What have you learned from it? Are there any links showing how to make one?
Inquiring Minds want to know!
Post a Followup:
| FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
||||||||||||||
This post is made possible by the generous support of people like you and our sponsors:
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2024, Audio Asylum, all rights reserved ]
