[sdiy] Osamau Hoshoyama's single-ended diode ladder VCF

[HOSHUYAMA]

Anthony,

Actually, my single-ended diode ladder can be considered as a 4-pole 
variant of Steiner VCF.  It's not so complicated.

   http://www5b.biglobe.ne.jp/~houshu/synth/Vcf0111.gif

3n3F will be OK.  I used 5n6F just because I had a bag of capacitors 
with the value.  In the original Steiner filter, 2n2F's are used. 
Matching of the corresponding capacitors will bring less CV 
bleedthrough.  I'm sorry to say I have no idea on oil
capacitors.

Buffer (recovering) amp will be the biggest issue with the VCF.
Signal level at the center of the diode string is very small.
I struggled and managed to obtain smooth resonance by using two opamps
with a little strange equalization.  However, I can't guarantee the 
values of the components are appropriate for you.  If you adopt 4-pole 
Sallen-Key structure, design of signal level will be much easier.

Anyway, thanks a lot for your interest on my schematics.
I hope you understand my explanation in broken English.

Best regards,

Sam Hoshuyama
Saitama, JAPAN

anthony wrote:
> This has looked like a good filter to build to me for a while. I was wondering if anyone has had any luck with it. I have a huge batched of diodes matched to 10uV so I'm set there.
> But I've heard that it's good to have fairly matched capacitors in ladder filters as well. I only enough of 1 kind. They are marked 3n3F (which is less than in the schematic but still a good value for a filter I think). I don't know the make and from the construction they look like paper in oil caps. 
> 
> Has anyone ever used MKP RFI filter caps in a synth app?
> 
>