[sdiy] HP from LP ?

[Pete Hartman]

Short answer is to subtract the LP output from the input.

More seriously, look at State Variable Filters, they produce HP, BP, and LP
from the same filter.

On Mon, Jul 31, 2017 at 1:10 PM, Michael Zacherl <sdiy-mz01 at blauwurf.info>
wrote:

> 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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