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Old 1st November 2006, 07:06 AM   #1
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Default Jitter blocking

Hi,
I'm planning to build a dac and I like to know how I can reduce the jitter. Now I know two different styles:

a) Using asynchronous sample rate converter (like AD1896)

b) Using spidf receiver and spidf transmitter:

http://www.akm.com/AppsNotes/Reclocker.htm

Which one would give better results in theory? What about the other jitter reducion techniques?
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Old 1st November 2006, 10:01 PM   #2
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dump USB and use 1394, connect directly to I2S = no detectible jitter.

See any 1394 DAC from these guys: http://m-audio.com and http://rolandus.com

( http://industrialcomponent.com/firew.../fws46603.html )
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Old 2nd November 2006, 09:01 AM   #3
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Quote:
Originally posted by FastEddy
dump USB and use 1394, connect directly to I2S = no detectible jitter.

See any 1394 DAC from these guys: http://m-audio.com and http://rolandus.com

( http://industrialcomponent.com/firew.../fws46603.html )

Whereas I2S has no data induced jiter as the clock is separate, the resulting jiter still depends on the clock quality.

Best is to have the clock at the DAC, and the source acting as a slave. I that case SPDIF also works well as interface

best

Guido
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Old 2nd November 2006, 10:38 AM   #4
el`Ol is offline el`Ol  Germany
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In my opinion adding random jitter is equivalent to blocking jitter, since it can cover regular jitter. The Nyquist frequency is especially sensitive to jitter, since it is phase-fixed (at least for acoustic music, electronic sound can be phase-fixed at any frequency). A method of adding random jitter more selectively to the Nyquist frequency would be the following:
*filter and upsample 32 times
*devide into blocks of 16 subsequent values
*use a random generator to select one of each block
*do 15th order interpolation
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Old 2nd November 2006, 05:14 PM   #5
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Guido Tent: " ... I2S has no data induced jitter as the clock is separate, the resulting jitter still depends on the clock quality. Best is to have the clock at the DAC, [with] the source acting as a slave [, slaved to the DAC clock]. In that case SPDIF also works well as interface best ..." (Pardon my editing above, a bad habit picked up techie geek white paper rewrites)

Mr. Tent has some other interesting thing to say on his web site about jitter, DACs & CD/DVD player quality: http://www.tentlabs.com/Products/cdupgrade/index.html ... http://www.tentlabs.com/Products/diycd/index.html ...

(One would hope that he will follow through soon with a "universal" DVD-A / SACD / DVD-V player or upgrade or possibly even a kit !! I would buy one in a New York minute ... do you take PayPal?)

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Old 3rd November 2006, 07:20 AM   #6
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Quote:
Originally posted by el`Ol
In my opinion adding random jitter is equivalent to blocking jitter, since it can cover regular jitter. The Nyquist frequency is especially sensitive to jitter, since it is phase-fixed (at least for acoustic music, electronic sound can be phase-fixed at any frequency). A method of adding random jitter more selectively to the Nyquist frequency would be the following:
*filter and upsample 32 times
*devide into blocks of 16 subsequent values
*use a random generator to select one of each block
*do 15th order interpolation

could you explain what is blocking jitter ?

best
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Old 3rd November 2006, 07:48 AM   #7
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Default Re: Jitter blocking

Quote:
Originally posted by macgyver
Hi,
I'm planning to build a dac and I like to know how I can reduce the jitter. Now I know two different styles:

a) Using asynchronous sample rate converter (like AD1896)

b) Using spidf receiver and spidf transmitter:

http://www.akm.com/AppsNotes/Reclocker.htm

Which one would give better results in theory? What about the other jitter reducion techniques?



Have I got something for you. Im an IC design engineer which has just happend to make a ASRC taht is 32bit accurate. Also, it has SPDIF I/O or even I2S/LJ/RJ I/O Any input format can be converted to output format too. If you want to know more, just let me know. By the way, the ASRC can "eat" 400ns of jitter and clean it up perfectly to the accuratacy of the output clock. (Which can be from a crystal or oscillar or something.


Dustin
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Old 3rd November 2006, 08:04 AM   #8
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Default Re: Re: Jitter blocking

Quote:
Originally posted by dusfor99





Have I got something for you. Im an IC design engineer which has just happend to make a ASRC taht is 32bit accurate. Also, it has SPDIF I/O or even I2S/LJ/RJ I/O Any input format can be converted to output format too. If you want to know more, just let me know. By the way, the ASRC can "eat" 400ns of jitter and clean it up perfectly to the accuratacy of the output clock. (Which can be from a crystal or oscillar or something.


Dustin
Tell some more What is that part, already in the markets?
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Old 3rd November 2006, 08:40 AM   #9
Nixie is offline Nixie  Canada
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Old 3rd November 2006, 09:08 AM   #10
el`Ol is offline el`Ol  Germany
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Quote:
Originally posted by Guido Tent



could you explain what is blocking jitter ?

best

With blocking jittter I mean having a recording/playback chain that has physically low jitter at any position in the chain. Random jitter at only one position can cover regular jitter no matter of whether it is before or after it.

Of course upsampling of min. factor 2 is essential, otherwise the Nyquist frequency is phase-fixed again.
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