[sdiy] Static ADC and DAC recommendations?

[Jim Patchell]

No Clocks and ADC are pretty much contradictory terms.  If you clock 
fast enough, the delay you get will be insignificant for use in a feed 
back loop.

If you do want a clockless converter, John Simonton wrote an article in 
a long past polyphony on how to do this with LM339's However while one 
LM339 will give you a 4 bit converter, the number of parts you will need 
really skyrockets for more bits. And even if you do make say an 8 bit 
converter, you are going to experience some rather nasty transients as 
the conveter trys to settle down and you are probably going to see some 
nasty banging around in the LSBs.

-Jim

On 1/17/2013 7:56 AM, cheater cheater wrote:
> Hi guys,
> I'm looking for a clock-less ADC which will output an 8-wire parallel
> bus of continuous signals. My initial thought was to implement a
> simple ADC with comparators, but I'm sure there has to be a chip like
> that as well. I have been unable to find anything like that, though.
>
> On the DAC front, the idea is to use an r2r DAC, and turn the parallel
> signal back to a normal analog signal. The DAC0800 is one option, but
> I'm sure there are others, so feel free to suggest anything.
>
> The idea here is to have a box which has an ADC the signal of which
> goes straight into a DAC. The two should work without a clock (so you
> can e.g. use it in feedback paths), and so that you can process the
> separate "bits" just like any other analog signal and see how the DAC
> racts to that. Additionally, being able to glitch out the ADC with
> too-fast signals is a plus.
>
> Perhaps being able to limit the current to the ADC section or even the
> various comparators, you could get things like cross-over distortion
> to become more prominent.
>
> It should be interesting to see how the signal degrades when the ADC's
> region of normal operation is exited - it shouldn't be aliasing
> anymore.
>
> Thanks
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