[sdiy] PWM or DAC better for audio out?

Noah Vawter nvawter at media.mit.edu
Thu Jun 2 20:26:48 CEST 2011


On Jun 2, 2011, at 1:36 PM, Veronica Merryfield wrote:

>
> On 2011-06-02, at 9:54 AM, Olivier Gillet wrote:
>
>> To get good resolutions, try sigma-delta modulation instead...
>
> My experience, albeit dealing with someone (pro synth maker) else's  
> output, has been that S-D DACs tend to be intrusively noisy.

Typically, what they do is move all the noise above the sampling rate.

So really, it's an e.g. 704 kHz (16x44.1kHz) DAC with lots of noise  
everywhere in the whole spectrum, except from 44kHz down...   in that  
area it's very precise.  It's precise because it has 16 cycles to  
create a signal that has an accumulated frequency spectrum identical  
to what you wrote to it.

So that noise could be very intrusive, but only to circuits  
"listening" to frequencies about 20kHz.  (there are RF issues, too,  
but that's getting off topic)





> Having said this, I am not sure of all the issues but wonder if they  
> are not over sampling enough or clocking it too slowly or have too  
> much variation in the clock of something.
>
> In one case, I know the DAC is a AK4382AVT.
>
>
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