[sdiy] Butterworth design

[Csaba Zvekan]

Sorry,

It's true it's probably off topic. But then again maybe not .I am  
trying to get some DCO's with a dsPIC and a PCM1753. That one requires  
that filter design. I guess I could use the two resistors in series.  
But my question is more if it is even relevant to the sound? Is it  
critical?

Csaba


On Jun 17, 2008, at 3:46 PM, Dave Magnuson wrote:

> Hi Csaba,
>
> This is an off-list reply
>
> Why not use a series combination?   4K7 + 560R gets you really close  
> (5260 ohm)
>
> Dave
>
> ----- Original Message ----- From: "Csaba Zvekan" <czvekan at gmail.com>
> To: <Synth-diy at dropmix.xs4all.nl>
> Sent: Tuesday, June 17, 2008 9:24 AM
> Subject: [sdiy] Butterworth design
>
>
>> Hi group,
>>
>> I am gonna have to design a Butterworth 2nd Order Low Pass Filter  
>> for  the Audio Output after a 24-bit Burr&Brown DAC PCM1753.
>> Now my little software for filter design from Texas Instrument is  
>> is suggesting a 5.23K resistor. If my cutoff frequency is supposed  
>> to be 24.1 kHz -60dB. Of course I don't have that value handy.
>> My question is if I'd use a 5K6 1% resistor it filters something  
>> like 22.5 kHz almost 2k off .
>> Is that very critical to the sound & distortion? Or are these just  
>> standard values /recommendation that have somewhat of a toleranc.
>> I mean the frequency is not even audible up in that range. Or am I  
>> loosing valuable high end frequencies with it.But still, I  
>> understand  it causes some digital noise from the ∆∑-DAC that  
>> needs filtering.  Does it have to be exact the frequency 24.1kHz?
>>
>> Csaba
>>
>>
>>
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>