[sdiy] Capacitors in Moog ladder filter

[Tim Heffield]

Hello Yves,

Thanks for the information.  I think I will stick to using the 0.022uF
(22nF) as well.  I was just wondering if there were other things to be aware
of.  By the way I breadboarded the Steiner filter last night and was very
impressed with it's performance.

Regards,

Tim

-----Original Message-----
From: Yves Usson [mailto:yves.usson at imag.fr]
Sent: Monday, April 26, 2004 3:31 AM
To: Tim Heffield
Subject: Re: [sdiy] Capacitors in Moog ladder filter


Hi

you are right ! The value of the ladder caps is responsible for the
frequency range. Personally I use 22nF caps for my ladder filters,
this gives an evenly distributed range (10Hz up to 22 000Hz).
If you use 100nF caps as in EFM designs you will lower the range toward
the bass
and the upper limit won't go higher than 8 000 Hz. As a matter of fact
Moog used 100nF in his Taurus Bass Synth.
As far as I am concerned I used 22nF caps for the VCF1 of the EFM
Wildcat and
for the VCF2F.

Cheers



> I have a question about the four caps in the Moog ladder filter.
> Looking
> through all my old documents and on the web I see values that range
> from
> 0.022uF to 0.1uF for the the four caps that create the poles.  It
> seems to
> me that this would just raise or lower the resonant freq for a given
> CV.
> Does anyone know if there is more to it than this?  I noticed that the
> Mini-Moog filter started out with 0.068uF and someone changed it to
> 0.027uF...was the cutoff frequency to low?  EFM seems to use 0.1uF on
> all of
> his filters.
>
> Tim
>
>
-------------------------------------------------------------
Yves Usson

Lab. TIMC UMR5525 CNRS
Institut d'Ingéniérie et de l'Information de Santé (IN3S)
Faculté de Médecine
Domaine de la Merci
38706 La Tronche cedex

email : yves.usson at imag.fr, yves.usson at ujf-grenoble.fr

tel.  (+33) (0)456 520 074
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