Jitter test signal - 11025+229.6875hz. How to ?

percy · 23rd April 2007, 07:37 PM

Ok so I dont have any fancy equipment to measure jitter.
All I have is a soundcard that I could use with a free spectrum analysis tool like Visual Analyser or rmaa or something to see how the spectrum looks like.

I came across this test signal which is nothing but 11025Hz sine wave toggled by a 229.6875 square wave. But I am not quite sure how to use it.

Spectrum analysis of the wav file shows a 11025hz signal flanked by sidebands at +/-229.6875 and then every 3rd order of 229.6875hz.

If I play this signal on the PC via loopback or record it from an external source (play from a CD player after burning it to a CDDA disc). I am not sure What should I look for in the recorded waveform ? Idential spectrum ? or only the 11025hz signal ? or.. ?

Bernhard · 24th April 2007, 11:03 AM

Quote:

Originally posted by percy

I came across this test signal which is nothing but 11025Hz sine wave toggled by a 229.6875 square wave. But I am not quite sure how to use it.

Me too.

ojg · 24th April 2007, 11:34 AM

The J-test signal was invented (I believe) by Julian Dunn. Read about it here, and how you can analyze the result to calculate the jitter in ps from the spectrum.

http://www.nanophon.com/audio/diagnose.pdf

jcx · 24th April 2007, 03:13 PM

I wouldn't expect loopback testing to be that useful, the best cards would use the same xtal for adc and dac, rendering jitter invisible as it would be common to both

the problem with testing is the requirement for superior test equipment performance over that of the tested system

percy · 24th April 2007, 10:35 PM

ok first let me get this straight -
The j-test signal would only helpful for evaluating the "interface" or "data" jitter. It won't really help give an idea about the clock jitter. Is that correct ?

FastEddy · 25th April 2007, 12:13 AM

Speaking of ... has anyone run any jitter tests on FireWire connected devices (ACD / DAC)? (Like this one: http://www.echoaudio.com/Products/Fi...ire4/index.php ?)

23rd April 2007, 07:37 PM	#1
percy diyAudio Member Join Date: Apr 2004 Location: MN	Jitter test signal - 11025+229.6875hz. How to ? Ok so I dont have any fancy equipment to measure jitter. All I have is a soundcard that I could use with a free spectrum analysis tool like Visual Analyser or rmaa or something to see how the spectrum looks like. I came across this test signal which is nothing but 11025Hz sine wave toggled by a 229.6875 square wave. But I am not quite sure how to use it. Spectrum analysis of the wav file shows a 11025hz signal flanked by sidebands at +/-229.6875 and then every 3rd order of 229.6875hz. If I play this signal on the PC via loopback or record it from an external source (play from a CD player after burning it to a CDDA disc). I am not sure What should I look for in the recorded waveform ? Idential spectrum ? or only the 11025hz signal ? or.. ?

25th April 2007, 12:13 AM	#6
FastEddy diyAudio Member Join Date: Jun 2006 Location: North Californie	Speaking of ... has anyone run any jitter tests on FireWire connected devices (ACD / DAC)? (Like this one: http://www.echoaudio.com/Products/Fi...ire4/index.php ?) __________________ Over compression is a problem with modern CD recordings

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24th April 2007, 11:34 AM	#3
ojg diyAudio Member Join Date: May 2003 Location: Norway	The J-test signal was invented (I believe) by Julian Dunn. Read about it here, and how you can analyze the result to calculate the jitter in ps from the spectrum. http://www.nanophon.com/audio/diagnose.pdf

24th April 2007, 03:13 PM	#4
jcx diyAudio Member Join Date: Feb 2003 Location: ..	I wouldn't expect loopback testing to be that useful, the best cards would use the same xtal for adc and dac, rendering jitter invisible as it would be common to both the problem with testing is the requirement for superior test equipment performance over that of the tested system

24th April 2007, 10:35 PM	#5
percy diyAudio Member Join Date: Apr 2004 Location: MN	ok first let me get this straight - The j-test signal would only helpful for evaluating the "interface" or "data" jitter. It won't really help give an idea about the clock jitter. Is that correct ?

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