LM13700 Wet Resonance Filter

Cynosure · Posted: Fri Nov 11, 2011 12:14 am Post subject: LM13700 Wet Resonance Filter

Can anyone recommend a lowpass filter schematic to use with the LM13700 that has a very wet sounding resonance? I currently have the wasp filter on breadboard using this chip in place of the two 3080's. It sounds good, but I want that wet mushy sound I know you can get with the LM13700.

My circuit is running on +5/0/-5 - not sure if that makes a difference or not.

bod · Joined: Apr 28, 2009 Posts: 148 Location: Glasgow

fill a bucket with water, throw in your speakers, plug it all in, stand well back...

for extra wobble factor, try adding a little gelatine. Wink

(sorry)

what pot and resistor do you have in the resonance feedback loop?

Cynosure · Posted: Fri Nov 11, 2011 7:07 am Post subject:

I made this one:

http://electro-music.com/forum/phpbb-files/wasppercent20filterpercent20clone_2_165.pdf

I used a 50k pot instead of 47k for the resonance (and 50k for the cutoff too).

bod · Joined: Apr 28, 2009 Posts: 148 Location: Glasgow

you could try reducing R23 to increase the amount of resonance when the pot is maxed, but i'm not sure that would give you the effect youre looking for.

Cynosure · Posted: Fri Nov 11, 2011 8:28 am Post subject:

Thanks bod. It was determined in chat that I need to modulate it was an envelope to get the zap I'm looking for.

tjookum · Posted: Sun Nov 13, 2011 6:44 am Post subject:

I happen to have this circuit on my breadboard and changing R23 to 20k does add more resonance but it also makes the output drop a little.

comrade_zero · Posted: Wed Nov 16, 2011 11:09 pm Post subject:

Have you tried the filter from the MFOS soundlab? If bipolar power is o.k. then it is a really simple 13700 filter that sounds good. ericarcher.net has a 13700 filter adapted to run off a single 9v supply. Both of these are basically adaptations of the data sheet filter (state variable with resonance).
I've played with the WASP filter and it always seems a little "thin," if bipolar is an option you might want to try the MFOS...
Good luck, hope this helps.

Cynosure · Posted: Thu Nov 17, 2011 6:43 am Post subject:

Thanks for the info tjookum and comrade_zero.

I ended up going with a dual wasp, so I have twice the resonance when I need it. Also, I came up with a cmos controlled decay circuit that helps give the zap I was looking for at the beginning of the sound.

Dual supply is an option, so I will check out the mfos one as a modular option for another project, but I have ran out of room with this one.