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Nikon1975 22nd August 2010 10:26 AM

spdif signal generator
Dear All,

Just curious: what do you use to test DACs and other digital sources ? Do you have something like an spdif signal generator ? I understand that a PC can be used, but I am wondering if the frequency limitations that the software signal generators have depend on the sound card. Do you think it is possible to generate a 50 kHz signal with the PC using the spdif out, or some interface like the hiface ?



kipman725 22nd August 2010 10:49 AM

yep as long as the sample rate is set high enough on the PC, IE 192Khz for >48Khz. However why would 50Khz be on interest? you can't hear it.

Nikon1975 22nd August 2010 11:49 PM

50 khz was just a number to say "something above the audio range" , I was curious to see what is the pass band of the DAC chip. Any software recommendation ? for MAC would be optimal, but windows is fine as well.

What is difficult then to check with such a setup is the phase of the signal, as I cannot see how I can have a common time base between the input and the output.


jcx 23rd August 2010 02:18 AM

PC soundcard record/capture can have significant latency - single digit ms is considered acceptable, more annoys musicians trying to add/layer tracks

hitting a defined in/out relative phase at 50KHz is simply beyond current technology PC audio - if you need such resolution you need to include markers in your source file and determine phase with respect to them in the recorded output

for most soundcards the skew between channels should be very small and stable, recording analog stimulus signal and tested device output to different soundcard ADC channels is another solution to acquiring precise phase information

I have used Ltspice to create complicated .wav at higher sample rate/resolutions and used Audacity open source sound editor to play/record on a pci soundcard- but haven't tried to determine or make measurements that would rely on the latencey

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