Putting a pot in the filter’s input helped alot!
It’s sounding way better than it did before, but I’m still noticing some weirdness. When the resonance is high, and I fiddle with the vco pitch, the sound will begin to jump (not really sure how else to describe it). Is the filter supposed to do this?
Not supposed to do that, but it sounds funky 
I guess you could say it’s a happy accident 
One of my favorite weird glitch sounds was a magic knob on a Jen monosynth. Magic until I noticed the pot was dirty and could use an earth.
With the pot clean, the virtuoso glitch was gone forever. With the Ground attached it never again screamed a gritty solo and the phatt bass became just phhht.
If you like the behavior it was played for and got.
That’s a bummer about your Jen synth. Your story swayed me to keep the filter how it is quirks and all! I think I’ll just build a second one that’s more reliable, and use this one when I need some extra grit.
I’m truly touched that my comments saved the only filter of it’s kind. Bravo for making another filter.
The correct number of unique filters in any modular is a function of
(nF. Req = nF. Got +1)
Are you sure that’s an MS20 filter and not an APC?
An APC?? What’s that?
A simple 555 oscillator known as the Atari Punk Console.
Hi I’m having a stranger problem yet, to start just connecting the output to the mixer and generates me a signal as triangular, the input in does not recognize the signal sent from my vco is as if I did not insert anything, instead by connecting it to the CV begins to generate sound cutting frequencies and excitation at resonance, I do not know if I should connect all jack inputs to GND in fact the in if I connected it to gnd but I still have the same problem no signal input.
Hello and welcome in the forum 
Yes all the jacks must be connected to GND. It is a missing on Sam’s schem.
If this is the simple version that you made
Hi fredik, I had this issue when the CV input went too low. I swapped the TL074 for an LM324 and it works great now. Thanks!
Just build one of the ms20 filter on strip board but I ve also order few mount ago to Sam shop one kosmo filter … I have a issue is the led which blink because I don’t put them in the right way gonna do this tomorrow because it’s late in France…. I gonna come back to ask you how to fix my filter 
…
I got a issue I didn’t get any sound coming out from my filter I fix the led problem but one is it is stay light up don’t know if it normal I wait for u answer if u know what to do I think it’s a little fix
The leds should shine only when the resonance and the cut off are increased. The pots at zero, they should not light up.
Check maybe the connection of your leds, they must be connected in opposite polarity
You’re supposed to use the same type of LED in both directions in the feedback loop, otherwise your filter will behave weirdly (depending on type, blue LEDs may have a much higher forward voltage than green LEDs, i.e. they need more signal before they light up). On the other hand, this asymmetry may result in a sound you like, so not saying that what you have now is all wrong…
Hi all.
I’m having some problems with the LMNC filter.
I’m trying to debug the issue.
With the power off and chips removed.
I have a resistance of 4.7k between pins 6 and 11 of the LM13700.
And 4.7k between pins 4 and 11 of the TL074.
I’m also getting the same 4.7k resistance between +12v input and -12v inputs.
And 100K between +12v and ground.
And 100K between -12v and ground.
I’m convinced everything is wired correctly.
When I power it up the lm13700 pops!
I’ve built the circuit twice and have blown 6 LM13700 so far.
Does anyone have a list of readings I should be getting between the pins of the IC’s?
I’m very frustrated.
I can post pictures later of that helps.
Thanks
Did you read this?
If the circuit is built correctly the control current to the LM13700, which is the main suspect if one blows, should be safe. You need to verify the 10k resistors. Measuring resistances in circuit is rarely useful, but you can at least verify the color codes are correct.
Other than that:
And yes photos (top and bottom) would help.
Yea I did read that post.
I’m building the simple VCF not the performance one.
I’ll get some photos posted tonight.
Thank you.
If you mean this one
it is more or less the same schematic, just on stripboard instead of PCB. And this
may be helpful.
