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Thread: Audio DAC Accuracy [Tech]
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picon face BY : Brandon, Tom email (remove spam text)



I am looking at a project where I would like to synthesise various audio
waveforms. Looking at sine, square etc 20Hz-24kHz.etc. My question is in
regards to the accuracy of DAC needed. Now, typically Audio applications use
16+ bit at 44.1 and up. I have no problems with the sample rate, it has to
be at least double the highest  frequency of interest and close to double
will produce very low quality sine waves (e.g. CD audio, 20kHZ sine @
44.1kHz = ~2.2 samples\cycle) hence most audio converters use 8 to 16x
oversampling so you're looking at about 350kHz (44.1 @ 8x).

But what effect will bit depth have on the reproduction? Obviously it will
introduce larger step sizes and thus less smooth curves. If you're
reproducing complex signals I could see it effecting the
reproduction\capture of appropriate sines. Slight nonlinearities may not be
able to be filtered out as easily due to the complex source. But, Ig all
you're producing is single oscillators then what sort of accuracy would be
needed?

Also, for the same project I'd like to use 1 DAC to drive a few SHAs to do
mutlichannel. I've seen one SHA capable of >12bit (an Analog devices 16bit
SHA) based on DNL and this was only single channel. Does anyone know of a
multi channel SHA with a DNL suitable for 14+ bits ideally with settling
time to suit 1-2MHz. Also, I'm still looking for a DAC capable of 14+ bits @
>1MHz at a reasonable price.

Thanks,
Tom.

<F08121B734E0D311804300105A7890F7719F@psynt.psy.unsw.EDU.AU>

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