Re: [AH] HPF from LPF (was Re: [AH] system 100 versus 100m)

From Jonathon Stevens
Sent Wed, Nov 9th 2005, 23:11

Cool idea. But with most filter designs there's a certain amount of phase 
shifting so I wonder if with some filter designs you may end up with more of 
a notch filter effect?  Or at least depending on what filters you do this 
with you may get closer or farther from the target.

Do any modular synth companies sell an All-Pass filter module?  You could 
use this to continuously vary the phase of a signal, or...?


>From: David Evans <redacted@example.com>
>To: Mike Kent <redacted@example.com>
>CC: synth ollie <redacted@example.com>,        Analogue Heaven AH 
><redacted@example.com>
>Subject: Re: [AH] HPF from LPF  (was Re: [AH] system 100 versus 100m)
>Date: Wed, 9 Nov 2005 13:57:39 -0500
>
>On Wed, Nov 09, 2005 at 10:46:30AM -0800, Mike Kent wrote:
> > If you send a signal into a low pass filter and then mix it back with 
>the
> > original signal with reverse polarity, you can emulate a High Pass 
>Filter.
> >
>
>...
>
> > It works in theory but I've never actually tried it.
>
>   This is an idiom in Synthi programming.  I used to do it all the time on
>my A and it worked fairly well.  Fiddling with the levels is required,
>though.
>
>--
>David Evans
>Faculty of Computer Science                     redacted@example.com
>Dalhousie University, Halifax, Canada  http://bbcr.uwaterloo.ca/~dfevans/