KVR Audio

Richard_Synapse · Post by **Richard_Synapse** » Tue May 08, 2012 9:59 am

Does anyone know of analog synths employing a bandpass/bandstop/highpass filter design which is not state-variable? (it seems rather few analog synths have a multimode filter to begin with)

Richard

antto · Post by **antto** » Tue May 08, 2012 10:20 am

moog multimode ladder, i *think* it's not SVF

Richard_Synapse · Post by **Richard_Synapse** » Tue May 08, 2012 10:45 am

Used where? I don't know of any Moog synth with a multimode filter.

Richard

jupiter8 · Post by **jupiter8** » Tue May 08, 2012 12:08 pm

Not entierly sure what a SVF really is but how about the Oberheim Matrix 12/XPander ? Don't think they're SVF.

Ichad.c · Post by **Ichad.c** » Tue May 08, 2012 12:44 pm

The Korg35 as used in the MS10 and MS20 are Sallen-Key types and not SV filters.

Google:

A Study of the Korg
MS10 & MS20 Filters
Timothy E. Stinchcombe

Regards
Andrew

Richard_Synapse · Post by **Richard_Synapse** » Tue May 08, 2012 2:30 pm

True, thanks- never looked at the Korg filters in detail.

Btw the reason I ask is that it doesn't seem to be straightforward to transform a nonlinear filter design (e.g. the Moog ladder) to bandpass, notch or highpass.

Richard

Ichad.c · Post by **Ichad.c** » Tue May 08, 2012 2:45 pm

Have you looked at what I call "mystran's Biquad to SV Filter"? (he didn't give it a name,yet). It's mentioned on some filter related thread here at KVR. Could do any response that a biquad can - same formulas + conversion. But with better stability and is also delayless I think.

Andrew

mystran · Post by **mystran** » Tue May 08, 2012 3:38 pm

Richard_Synapse wrote:Does anyone know of analog synths employing a bandpass/bandstop/highpass filter design which is not state-variable? (it seems rather few analog synths have a multimode filter to begin with)

Richard

Korg MS filters and Xpander modes (summing outputs from the individual stages of a 4-pole/3-pole cascade) come to mind first. The latter is explained in the service manual (or in a tutorial thread I wrote here years back, which I can't seem to find right now).

mystran · Post by **mystran** » Tue May 08, 2012 3:50 pm

Ichad.c wrote:Have you looked at what I call "mystran's Biquad to SV Filter"? (he didn't give it a name,yet). It's mentioned on some filter related thread here at KVR. Could do any response that a biquad can - same formulas + conversion. But with better stability and is also delayless I think.

First of all, he asked specifically about analog synths and not SVF.

Ignoring those two points, I'm not sure which one you refer to, but if it's the one I wrote about a while ago, I've recently come to believe that you would be better served with this one which is just "delayless" discretization of SVF using TDF2 integrators.

However, I strongly believe it makes sense to keep this thread on the topic of analog synth filters not based on SVF.

whyterabbyt · Post by **whyterabbyt** » Tue May 08, 2012 4:01 pm

What about the Steiner-Parker Synthacon's filter? No notch filter, but has BP, LP and HP inputs, not outputs.

http://en.wikipedia.org/wiki/Steiner-Parker_Synthacon

http://www.cgs.synth.net/modules/cgs35_syntha_vcf.html

mystran · Post by **mystran** » Tue May 08, 2012 4:12 pm

Searching for non-usual filters I just found this: http://www.korganalogue.net/korgother/D ... ervice.pdf

Based on a quick look it's a 4-pole OTA cascade where the resonance feedback goes to the "ground side" of the 1st and 3rd capacitor.. it's got a switch for LP (that routes input to first stage as usual) or BP that routes the input to the resonance path so it probably qualifies as a multi-mode. No idea how it sounds.

Ichad.c · Post by **Ichad.c** » Tue May 08, 2012 4:51 pm

whyterabbyt wrote:What about the Steiner-Parker Synthacon's filter? No notch filter, but has BP, LP and HP inputs, not outputs.

http://en.wikipedia.org/wiki/Steiner-Parker_Synthacon

http://www.cgs.synth.net/modules/cgs35_syntha_vcf.html

That sounds like a fun filter!

Richard_Synapse · Post by **Richard_Synapse** » Tue May 08, 2012 5:18 pm

Wow, very interesting! Never heard of those synths before. I listened to some clips on the net, both filters sound very promising. They didn't specifically show off the bandpass/highpass though, so it's hard to tell anything in that regard.

Richard

brick · Post by **brick** » Tue May 08, 2012 5:24 pm

whyterabbyt wrote:What about the Steiner-Parker Synthacon's filter? No notch filter, but has BP, LP and HP inputs, not outputs.

http://en.wikipedia.org/wiki/Steiner-Parker_Synthacon

http://www.cgs.synth.net/modules/cgs35_syntha_vcf.html

The most awesome sounding filter , those original units are so rare . Never quite heard any of the Synthacon filter clones hit the spot . Love to hear it done right in software.....

@Richard , check out the Dual Wasp filter :

mystran · Post by **mystran** » Tue May 08, 2012 5:30 pm

brick wrote: @Richard , check out the Dual Wasp filter :

That's a SVF.. though granted it's an unusual implementation.

Analog BP/BS/HP filters (not SVF)