[sdiy] Passive filters and impedances

[Richie Burnett]

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...

That will reduce the loading effect of each stage on the previous one, and help prevent the poles moving apart.

-Richie,

Sent from my Xperia SP on O2

---- Donald Tillman wrote ----

>
>> On Oct 31, 2015, at 10:07 AM, Richie Burnett <rburnett at richieburnett.co.uk> wrote:
>> 
>> In general we don't usually build filters like this because the lack of buffering causes loading effects that move the filter poles.
>
>That's how the Roland Diode Ladder filter works.
>
>And slight variations of simple RC ladders are used all over guitar amplifiers.  Like the "slope" control on the Marshall JCM 800 bass amp.  Or the weird tone controls in the Sound City amps.  The Gibson GA-40.  There are several other examples I'm not thinking of right now.
>
>  -- Don
>
>--
>Don Tillman
>Palo Alto, California
>don at till.com
>http://www.till.com
>
>
>
>
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