making a simple VCF

[julieCabazon]

hi forum,
i'm trying to design a state-variable VCF with a much simpler layout than some of the examples i've come across. the main examples i've looked at are the electro-notes and ray wilson designs, which are related..but the former uses 3080s and the latter seems to use a lot of parts.

i guess the ideal would be a 13700-based design with a less sophisticated exponential generator..and maybe without all the op amps..

does anyone know of any such circuits? is it possible to use the 13700 buffers in place of the op amps?

cheers!

[steved]

I made a few of theses with 13700
still use a quad opamp but no problem .

http://electro-music.com/forum/topic-34426.html


I love the entire 'A collection of circuits by Nicolas' sticky thread

[Cynosure]

LM13700 datasheet has an example of one. Adjust the cap values to suit your needs. Change the feedback resistor with a pot for variable resonance.

If you need expo CV control then you will have to add that to the CV input.

[comrade_zero]

EFM 4621 Sem-style VCF: http://www.modular.fonik.de/files/EFMforum/orgEFMfiles/efm-4600-doc_01.pdf (p.15 of this pdf.) This is about as dead-simple as you can get for a state-variable filter with exponential frequency response. Use an lm13700. You may want to try some different cap values to taste.
Good luck, hope this helps.
c_z

[Cynosure]

Nice schematic! That is super simple. I would add some buffers and actively mix the CV inputs, but that is just me being picky. As is, that is about as simple as you can get.

Note - I think the thing that looks like a diode is the LM's buffer.

[gabbagabi]

Hi,

I had this one: http://electro-music.com/forum/post-426134.html#426134 on the Breadboard yesterday. may you find it usefull.

Cheers BB,
gabbagabi