[granodemostasa]

Okay, so everywhere people talk about jitter, they want to avoid it, there are cables, transports, and dacs that claim things about it. there are clocks and discussions and arguments and every such thing. what does it sound like, why do you want to avoid it and how does it happen?

not sure if this should go here or some other place so i posted it here.
Edit: okay, this has nothing to do with the above but i thought i should post it here instead of posting anywhere else:
http://shop.v-moda.com/pc-14-2-remix-metal-class.aspx
These are nice looking earbuds

 

[Ferbose]

Jitter comes in different types.
They can occur at different frequencies.
Some are signal dependent and some are not.

Normally jitter causes treble harshness, though the jitter may be in the midrange.
Also, it can reduce ambience or subtle details.

 

[NotJeffBuckley]

Jitter doesn't sound like much. Even entry level equipment reduces jitter to negligability. People cite vague improvements but if you observe you'll notice a lack of coherence to different folks' impressions of the same phenomenon.

Edit: Jitter is the loss or introduction of bits in inappropriate places, resulting from inconsistant clocking among different components in the signal chain. All such devices utilize jitter correction methods, some more robust (and often unnecessarily more so) than others.

 

[applebook]

For your reading pleasure, http://www.stereophile.com/reference...ter/index.html

Jitter introduces distortion that while can't really be idenitified at all times, the noise obscures or completely kills details (esp. subtle details) that is on the original recording. Cheap sources that you'd find at bestbuy will sound decent, but a good DAC/ source with high jitter rejection and solid circuit design will reveal micro-details that you've never heard before, particularly in the mid-range, where most of the "action" happens. Bass should go deeper, and highs should reach much higher without disortion...

...but this is all dependent on the original source material. An undynamic and undetailed CD is never going to sound brilliant with any source, period --thus the main reason why most pop recordings are garbage (because they're usually fed into a garbage bin).

 

[Lsportline43]

So what is at fault for jitter? The DAC? Or is it the digital source itself?

The reason why I am asking is because I heard someone say that the optical digital signal of the iRiver H120 has a lot of jitter.

Also can some clear up what comes before the DAC? I know the digital source feeds the DAC and the DAC feeds the amp... but what is it that reads the digital data? Are there difference in quality of digital readers?

 

[Carl]

Jitter sounds like wrong. How's that for an English sentence.

The stuff doesn't have a defining sound colouration that you can put your finger on, it just makes the music harsh and unnatural, and sound less like it is live.


The stuff affects the music because delta-sigma DACs work on a high-speed swiching principle (imagine a guy toggling a switch that has only two choices; "up" and "down", really, really fast, trying to recreate a sine wave), and any timing errors confuse the hell out of them (making them go up and down at the wrong times, and thus unable to make the sine wave properly). Analogue music, like from vinyl and cassettes, is always a perfect wave, but CD players, MP3 players, and their ilk can't quite reach that goal in reality. At the very least they can keep jitter to a minimum so that they get very, very close to the goal.

There are other kinds of DACs that don't use the high speed switching principle (namely sign-magnitude DACs and PWM converters) that work on slower, but more accurate, techniques, and are thus not affected by jitter as much. However, they aren't used as much as they (in my opinion) should be.

 

[Ferbose]

Quote:

Originally Posted by NotJeffBuckley Edit: Jitter is the loss or introduction of bits in inappropriate places, resulting from inconsistant clocking among different components in the signal chain. All such devices utilize jitter correction methods, some more robust (and often unnecessarily more so) than others.

Jitter has nothing to do with bits. It is analog in nature. Jitter is the clock inaccuracy in A/D or D/A conversion. Jitter exists because there is no perfect clock and can get progressively worse as clock signal is transmitted in the system, or by interference. Of course there are methods to correct for jitter but complete elimination is impossible.

 

[Ferbose]

Quote:

Originally Posted by Carl Analogue music, like from vinyl and cassettes, is always a perfect wave

Not really. There is really no way to spin a vinyl disc at an absolutely constant speed. I think the disortion due to spin speed variation is called wow and flutter, which are quite audible.

 

[Carl]

Quote:

Originally Posted by Ferbose Not really. There is really no way to spin a vinyl disc at an absolutely constant speed. I think the disortion due to spin speed variation is called wow and flutter, which are quite audible.

You're right. The analogue domain has wow and flutter.

Wow and flutter has quite a different (but equally hard to describe) effect on the sonic signature from jitter.

 

[UezeU]

I can just see high-end components integrating atomic clocks soon, they're pretty accurate.

 

[Carl]

Quote:

Originally Posted by UezeU I can just see high-end components integrating atomic clocks soon, they're pretty accurate.

The best way to reduce jitter is to genlock the components together, use a low-jitter interface like I2S, and use the most downstream device as the master.

The reason why all external transport-DAC combos don't come that way is that they wouldn't be able to charge mega-bucks for esoteric psuedo-science clocking technques for SPDIF outputs that way.

 

[Ferbose]

Quote:

Originally Posted by UezeU I can just see high-end components integrating atomic clocks soon, they're pretty accurate.

JVC uses atomic clock to drive A/D converter in their XRCD mastering.
If JVC would release the hi-rez master of XRCD, it should sound amazing.

Now rubidium atomic clock is coming to home audio:
http://www.teac.com/esoteric/NewEsoteric/G-0s_G-0.html

However, the new Zanden DAC rejected rubidium clock because the designer dislikes the sound. It uses some kind of double-ovened crystal IC, I think.

 

[Ferbose]

Quote:

Originally Posted by Carl The best way to reduce jitter is to genlock the components together, use a low-jitter interface like I2S, and use the most downstream device as the master.

I second that.
However consumer audio is designed around I2S, and it won't be for a long time to come.

 

[JJ15k]

yeah, it won t because of what carl said, if they did they wouldn t be able to advertise "jitter reduction " as a feature.

 

[Ferbose]

Quote:

Originally Posted by JJ15k yeah, it won t because of what carl said, if they did they wouldn t be able to advertise "jitter reduction " as a feature.

More like because in consumer audio market compatibility is a big issue.
And because audiophiles like exotic solutions rather than sensible ones.