[sdiy] simple 8k lowpass for ADC?

[Dan Snazelle]

thanks!



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----------------------------------------
> From: czvekan at gmail.com
> To: synth-diy at dropmix.xs4all.nl
> Subject: Re: [sdiy] simple 8k lowpass for ADC?
> Date: Mon, 20 Jul 2009 23:16:59 +0200
>
> Hi Dan,
>
> I prefer this little piece of software from Texas Instruments. You can
> download it for free . It runs under Windows or on a MAC in a
> VirtualBOX session.
>
> http://focus.ti.com/docs/toolsw/folders/print/filterpro.html
>
> hope this was useful to you.
>
> Csaba
>
> On Jul 20, 2009, at 8:15 PM, 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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