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.. ?
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.. ?
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
http://www.nanophon.com/audio/diagnose.pdf
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
the problem with testing is the requirement for superior test equipment performance over that of the tested system
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 ?
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 ?
Speaking of ... has anyone run any jitter tests on FireWire connected devices (ACD / DAC)? (Like this one: http://www.echoaudio.com/Products/FireWire/AudioFire4/index.php ?) 😕
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