[sdiy] Multi-Input filters

[John Loffink]

Adding to your list;
24 dB rolloff, Butterworth highpass and lowpass
Wavemakers 822 Integrated Processing System (part of Wavemaker 4
synthesizer)
PWM/switched capacitor filters

John Loffink
jloffink at austin.rr.com 

> -----Original Message-----
> From: owner-synth-diy at dropmix.xs4all.nl [mailto:owner-synth-
> diy at dropmix.xs4all.nl] On Behalf Of Grant Richter
> Sent: Monday, February 10, 2003 3:00 PM
> To: Theo; Osamu (Sam) HOSHUYAMA; Tim Ressel
> Cc: Synth-Diy
> Subject: Re: [sdiy] Multi-Input filters
> 
> I have been working on the BIG filter chart. That is, take each filter
> topology and cross it with each transconductor type.
> 
> Lots of mistakes here, please correct!
> 
> For example:
> 
> Typology: 24 dB Rolloff (mostly Butterworth lowpass)
> Transconductor
> 
> Transistor: Moog 904A & later
> Diode: EMS Synthi
> 
> OTAs
> 3080: Star Synare
> 13700: Wiard Omni
> 3280: Patchell
> Discrete: Jurgens 20xx
> Hybrid: Arp 4072?
> 
> CMOS VCR: ?
> 
> Opto-coupler: Wiard "Boogie" filter (shipping in March)
> 
> Typology: State Variable
> Transconductor
> 
> Transistor: ?
> Diode: ?
> 
> OTAs
> 3080: Aries 3xx
> 13700: Evenfall Mini-Modular
> 3280: Patchell
> Discrete: ?
> Hybrid: ?
> 
> CMOS VCR: ?
> 
> Opto-coupler: Wiard "Don't Bother" filter
> 
> Typology: Sallen-Key
> Transconductor
> 
> Transistor: ?
> Diode: Steiner-Parker
> 
> OTAs
> 3080: ?
> 13700: Korg MS-20
> 3280: Patchell
> Discrete: ?
> Hybrid: ?
> 
> CMOS VCR: ?
> 
> Opto-coupler: Buchla & Wiard Borg
> 
> Only one example is listed for each type, please add more info if you
have
> it. Each blank spot is a potential new filter design.
> 
> Since I like the sound of Vactrols I have been building each topology
from
> them as in the Borg and Boogie designs. A Vactrol State Variable or
Biquad
> sounds just as plain vanilla as any other SV implementation (IMHO).
> 
> I have noticed the topology is far more important to the
characteristic
> sound of a filter than the actual transconductor.