[sdiy] Oberheim Xpander Multimode VCF Question

[Adam Schabtach]

There's also this project/PCB:
http://m.bareille.free.fr/modular1/vcf_multimode/extrapole.htm

However, am I mis-remembering, or wasn't there a thread about this sort of
multimode VCF re-configuration a couple of years back, and wasn't it stated
that the levels of each filter stage have to be so precisely established
that even 1% resistors aren't adequate, and that it was speculated that
Oberheim must have hand-matched resistors to build the Xpander filter?

--Adam

> -----Original Message-----
> From: synth-diy-bounces at dropmix.xs4all.nl 
> [mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of Jay 
> Schwichtenberg
> Sent: Friday, March 12, 2010 9:14 AM
> To: synth-diy at dropmix.xs4all.nl
> Subject: Re: [sdiy] Oberheim Xpander Multimode VCF Question
> 
> I think a lot but don't actually get a lot done. But here is 
> what I thought would make an interesting filter experiment.
> 
> Buy one of Tim's (Magic Smoke) Mankato filters and some extra 
> SSM2164s. You have the filter taps coming off the board so 
> take those and run them into a quad 2164 VCA and fold that 
> back into the filter like the OBie filter does.
> Add some static pots and VC input to control the VCAs. Could 
> be interesting.
> 
> Jay S.
> 
> > -----Original Message-----
> > From: synth-diy-bounces at dropmix.xs4all.nl
> > [mailto:synth-diy-bounces at dropmix.xs4all.nl]On Behalf Of Magnus 
> > Danielson
> > Sent: Friday, March 12, 2010 1:23 AM
> > To: karl dalen
> > Cc: synth-diy at dropmix.xs4all.nl
> > Subject: Re: [sdiy] Oberheim Xpander Multimode VCF Question
> >
> >
> > karl dalen wrote:
> > > Or simply take five trim pots one for each tap and trim 
> until your 
> > > ears declares a nice swoosh sound.
> > > Sometimes what looks neat on paper dont sound to interesting.
> >
> > Certainly... but he asked for a 4-pole all-pass.
> >
> > What makes a good sound is an entirely different matter.
> >
> > Also, I assume that the output of that all-pass would be mixed with 
> > the input for the null-cancelling effect of a phaser.
> >
> > The nice thing about the Xpander filter is that it allows 
> easy access 
> > to a number of unusual combinations that very easily can be 
> accessed 
> > and chosen among to find what fits a particular sound best.
> >
> > The rigid-ness of low-pass/high-pass and possibly band-pass is not 
> > necesserilly what is musically most usefull or meaningfull.
> >
> > Cheers,
> > Magnus
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> 
> 
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