[sdiy] TomG's 9v diode ladder VCF

[tomg@efm]

Try this version....You could say I made it for Ben but everybody
should enjoy this one...it's dead simple!
http://groups.yahoo.com/group/EFM_Synth/files/cookbook/vcf6se-sd.gif

Untested 2x2" DIY layout....but confidence is high! Somebody do it up
real quick so Ben will know it works.....
http://groups.yahoo.com/group/EFM_Synth/files/cookbook/vcf6se-pc.gif

It's 2 ics 12 diodes and 1 dual-npn (or matched 3904s) 16 resistors
and 3 caps.....good luck..

Tom




> OK I'll do the hacks!  I tested it with random selected
> 1N4148 diodes.
>
> I too prefer the Transistor Ladder... but the diode ladder is
> nice too. I've heard that the differences are mainly to be found
> in advanced mathematics that hurts my head...
>
> In simple terms (as I understand it...) The Transistor ladder
> sections are better separated... the diode sections load each other
> more due to the lack of gain in the diodes. So the 24db filter starts to
> look more like 18db or so at some ladder currents.
>
> One place to get some matching is the capacitors... I'm using 2% in
> both filters.
>
> Anyone know about the difference between the original MiniMoog ladder
> (with the 150 ohm bias resistors) and the newer model (with the 1K
> bias resistors ???)
>
> H^) harry
>
>
> >From: DCMagnuson at aol.com
> >To: Plutonique9 at symbiocom.com, synth-diy at node12b53.a2000.nl
> >Subject: Re: [sdiy] TomG's 9v diode ladder VCF
> >Date: Thu, 12 Apr 2001 11:22:43 EDT
> >
> >In a message dated 4/12/01 10:51:00 AM Eastern Daylight Time,
> >paia2720 at hotmail.com writes:
> >
> > > You might want to consider a chip like the MAD1108 which has 8 diodes
> > >  in it. Diode PAIRS need to be matched... not the diodes in one "leg"
> > >
> > >  TomG's pc board for the diode ladder filter is not layed out this
way.
> >I'm
> > >  gonna hack it to be "improved" one day... but it works OK without
> > >  any matching as well...
> >
> >I have one of Tom G's VCF-6's, and I used no diode matching at all (I
used
> >1N914's) .  The filter sounds good to my ears, but I don't have a matched
> >VCF
> >to compare it to.
> >
> >That said, I still prefer the sound of my 3046-based transistor ladder
VCF.
> >Does anyone know if the lack of diode matching could be the reason?  IE:
> >what
> >will the effects be because I did not match my diodes?
> >
> >Dave Magnuson
>
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