[sdiy] Craig Anderton's Multiple Identity Filter

[Andrew Simper]

Hi David,

As far as I remember the Oberheim Matrix only had a fixed 4 pole
cascade type low pass filter, did you mean the Oberheim Xpander? If so
then yes this is the easier way to generate different responses by
taking weighted sums of the output of each stage, but you don't get
the "correct" responeses, you get sags above the cutoff in the band
pass and high pass modes, and amplitude attenuation below cutoff with
changing resonance in all modes, which kind of sounds like changing
the cutoff upwards with increasing resonance in band pass and high
pass modes, but the resonant peak stays put.

Cheers,

Andrew

On 27 October 2016 at 03:23, David G Dixon <dixon at mail.ubc.ca> wrote:
> I've got a filter design called the "Polaris" that gives nearly 30 different
> useful filter modes in a much simpler say than the MIF, and doesn't need a
> Curtis chip to do it.  Intellijel sells it for $229.  If you want to check
> it out, go here: https://intellijel.com/eurorack-modules/polaris/  It's
> based on a Roland-esque cascaded-stage four-pole filter, and takes
> inspiration from Grant Richter's old Oberheim Matrix multimode filter
> design, but it goes a fair bit further than that.  The mode switching is
> done with a microcontroller generating a 17-bit code which controls five
> analog switches, which I still don't know how to do, so I don't have a
> handmade version of it yet.
>
>> -----Original Message-----
>> From: Synth-diy [mailto:synth-diy-bounces at dropmix.xs4all.nl]
>> On Behalf Of KA4HJH
>> Sent: Wednesday, October 26, 2016 8:55 AM
>> To: sdiy
>> Subject: Re: [sdiy] Craig Anderton's Multiple Identity Filter
>>
>> > On Oct 26, 2016, at 4:37 AM, Andrew Simper <andy at cytomic.com> wrote:
>> >
>> > From what I can see with Craig Anderton's filter it won't actually
>> > give the "correct" responses for all the different filter
>> types unless
>> > there is a way to switch the polarity of the resonance, and
>> also where
>> > the resonance is added. Am I missing something? Sorry if
>> I've posted
>> > all this stuff before.
>>
>> This is one of the reasons I reposted the link. I remember
>> some discussion about this and wondered how Craig's design compared.
>>
>>
>> > On Oct 26, 2016, at 12:30 AM, Doug Terrebonne
>> <dougt55 at yahoo.com> wrote:
>> >
>> > The MIF article has been on synthdiy.com for a long time -
>> > http://www.synthdiy.com/files/2002/MIF.pdf
>>
>> I didn't even know it was there.
>>
>>
>> > On Oct 26, 2016, at 5:43 AM, Roman Sowa <modular at go2.pl> wrote:
>> >
>> > Why use predatory file hosting sites while there are sites
>> like synthdiy.com or synth.net, which AFAIK are managed by
>> this list members.
>>
>> I completely forgot they existed but then this is the first
>> time I've received a complaint about Mediafire.
>>
>>
>> > On Oct 26, 2016, at 5:43 AM, Roman Sowa <modular at go2.pl> wrote:
>> >
>> > Why use predatory file hosting sites while there are sites
>> like synthdiy.com or synth.net, which AFAIK are managed by
>> this list members.
>> >
>> > If anyone's interested I can also host any doc files (no
>> audio/video/warez or any pirated stuff) at regular downolad
>> links, no ads, no download buttons or popups.
>>
>>
>> Good to know. I may take you up on it.
>>
>>
>> Terry Bowman, KA4HJH
>> "The Mac Doctor"
>>
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