Go Back   Home > Forums > Source & Line > Digital Line Level

Digital Line Level DACs, Digital Crossovers, Equalizers, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Thread Tools Search this Thread
Old 4th August 2009, 06:05 PM   #1
percy is offline percy  United States
diyAudio Member
Join Date: Apr 2004
Location: MN
Default Jitter - converting ps to db ?

How can one convert periodic jitter value from ps to -db, or vice versa ? For example, how can one find what would be the level relative to 0dbfs(-db) of the spikes that flank the fundamental signal for a known time value (200ps, 500ps, etc..).
  Reply With Quote
Old 5th August 2009, 08:27 PM   #2
poynton is offline poynton  United Kingdom
diyAudio Member
poynton's Avatar
Join Date: Mar 2005
Location: A life on the ocean waves when I'm not at home in N. Wales (but I'm not Welsh so no sheep jokes!)
As I understand it, the values quoted for 'jitter' are completely independant of signal level and therefore stand on their own merit.

attempts at equating are meaningless.

If it ain't broke, break it !! Then fix it again. It's called DIY !
  Reply With Quote
Old 5th August 2009, 09:02 PM   #3
diyAudio Member
Join Date: Nov 2006
Very roughly and not accurate for the theory

44.1kHz = 22.67us
if I have average 200ps jitter, some signal output from DAC will come 100ps faster / or 100ps later.

it will distort signal voltage level at each sampling time.
the distortion ratio estimation will be 200ps / 22.67us = about 9.0e-6 = about -100dB.
  Reply With Quote
Old 5th August 2009, 09:38 PM   #4
percy is offline percy  United States
diyAudio Member
Join Date: Apr 2004
Location: MN
so you can only 'measure' the spectrum amplitude of jitter, you can't compute it ?
  Reply With Quote
Old 6th August 2009, 12:17 AM   #5
diyAudio Member
Join Date: Nov 2006
simply, if all of PCM data are 0x0000, then DAC output is always 0V,
nothing happen by jitter.
terrible jitter cause .... still 0V output.
  Reply With Quote
Old 6th August 2009, 11:12 AM   #6
oshifis is offline oshifis  Hungary
diyAudio Member
Join Date: Mar 2004
Location: Budapest, Hungary
... and if all of the PCM data is 0xFFFF then a jitter peak amplitude of 1/44100s divided by 2^16 causes +/-1 bit error.
  Reply With Quote
Old 6th August 2009, 11:27 AM   #7
dmills is offline dmills  United Kingdom
diyAudio Member
Join Date: Aug 2008
Not quite: for any steady (DC) level, jitter has no effect.

You can consider jitter to be phase modulation of the recorded signal, and as phase is the time integral of frequency you can apply the analysis that applies to FM modulation to the problem.

Basically it comes down to bessel functions, and can be computed but it is not trivial and a simple conversion to db is not possible.

Matlab and Octave are both useful for visualizing this sort of thing.

Regards, Dan.
  Reply With Quote
Old 6th August 2009, 12:10 PM   #8
jkeny is offline jkeny  Ireland
Join Date: Feb 2007
Location: Dublin
Here ya go http://www.jittertime.com/resources/pncalc.shtml
  Reply With Quote


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
How much jitter... A 8 Digital Source 46 17th February 2013 02:29 PM
generate jitter test signal and measurign jitter using AP2? BJAMR Digital Source 11 1st November 2010 02:07 PM
Jitter in DAC. ghee0 Digital Source 44 3rd June 2010 09:25 AM
Data Jitter Versus Electrical Jitter? 300_baud Digital Source 8 16th July 2004 07:59 PM

New To Site? Need Help?

All times are GMT. The time now is 07:31 AM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2