[sdiy] Passive filters and impedances

[Mattias Rickardsson]

On 31 October 2015 at 23:09, Mattias Rickardsson <mr at analogue.org> wrote:
>> >
>> > ..., a good way to reduce the un-wanted interactions is to make the
>> > impedance of each RC filter stage about 10 times greater than the impedance
>> > of the preceding stage.
>
> When saying the impedance, do you mean the resistance?
>
> x10 for R, and x0.1 for C?
>
> Otherwise the filter will be some opposite of a brickwall filter... Japanese
> shōji paper wall filter perhaps. :-)

On 1 November 2015 at 19:05, Richie Burnett
<rburnett at richieburnett.co.uk> wrote:
>
> Yes, scale the impedances of the components by a factor of 10 for each successive stage...
>
> 1st stage: 1k with 100nF,
> 2nd stage: 10k with 10nF,
> 3rd stage: 100k with 1nF,
> etc...

Sorry, I had a brain drop accident and briefly forgot that the
impedance of a capacitor goes like 1/C. :o)

Anyway - has this impedance scaling technique ever been used to full
extent in any ladder filters, using different capacitor values for all
stages?

/mr