[sdiy] HP from LP ?

[Julian Schmidt]

Have a look at this paper on page 64, Multimode Ladder Filter
https://www.native-instruments.com/fileadmin/ni_media/downloads/pdf/VAFilterDesign_1.1.1.pdf

You can mix the different poles with a simple opamp mixer.
input -4 * Pole1 + 6 * Pole 2 -4 * Pole 3 + Pole 4 will yield a funky 
looking HP filter

julian


Am 31.07.2017 um 20:10 schrieb Michael Zacherl:
> Hi,
> I discussed that briefly in one of the last SDIY meetings,
> did some experiments but never came to a sound conclusion:
>
> Is there a ‘cheap’ way of turning a low pass filter into a high pass?
>
> How’s that possibly approached?
> Just something like subtracting the LP’s output from its input signal?
> If so, what about resonance?
>
> My point about doing that cheaply is the (upcoming) release of two synths with Moog ladder filter featuring a switchable high pass mode.
> To my knowledge, there was no resonating HP filter from Moog so far in any synth.
> Until now.
> Since both synths (Moog Mother-32 and Behringer Model D) are on the budget side in terms of money I’d rather expect a simple solution compared to a, say, DSI Pro-2 with two fully featured filters in it.
>
> Any hints?
> Thanks, Michael.
>
>
> --
> http://mz.klingt.org
>
>
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