[sdiy] simple 8k lowpass for ADC?

[Tom Wiltshire]

You could try one of these too - same thing really, but less mucking  
about:

http://www.ecelab.com/circuit-butterworth-lp.htm

T.

On 20 Jul 2009, at 19:15, Dan Snazelle wrote:

>
> i am putting audio ( a full track with vocals)  through an 8bit  
> converter. it sounds fine until the vocals get close to  
> sibilance...this
> seems to overload the converter and make the sibilance far far  
> worse to the point of almost white noise.
>
> now when i simply put an eq on the track in Logic FIRST i dont have  
> this issue.
>
> so i would love to build a simple filter into the circuit but dont  
> know what kind to use.
>
> in Logic I am using a roll off which kills everything above 8-10 k  
> (not a very steep curve)
>
>
> with this on there is no issue with the ADC0820 based  
> circuit....and i am NOT overloading the ADC
> as far as levels or voltage go. so this must be an aliasing issue  
> as the problem only arises when
> i sweep the sample rate toward lower clock rates.
>
>
> SO....i tried using simple RC filters but they are not really  
> working out too well.
>
>
> anyone have any advice on the kind of filters they use on an ADC?
>
> or maybe a homebrew switched cap filter i could clock off the clock?
>
> thanks
>
> (keep in mind this is meant to sound dirty anyway...just not crappy)
>
>
>
>
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