# Simple Ms20 vcf problem

**URL:** <https://lookmumnocomputer.discourse.group/t/simple-ms20-vcf-problem/4737>\
**Category:** KOSMO MODULES\
**Created:** [March 5, 2022, 2:42pm UTC](https://lookmumnocomputer.discourse.group/t/simple-ms20-vcf-problem/4737 "2022-03-05T14:42:56Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![Pat.bayle](https://avatars.discourse-cdn.com/v4/letter/p/9dc877/32.png) [@Pat.bayle](https://lookmumnocomputer.discourse.group/u/Pat.bayle)\
**Post date:** [March 5, 2022, 2:42pm UTC](https://lookmumnocomputer.discourse.group/t/simple-ms20-vcf-problem/4737/1 "2022-03-05T14:42:57Z")

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So ive just finished building the simple MS20 filter but stupidly wired the +12 and -12v the wrong way and blown the tl074.

Ive swapped both the tl074 and lm13700 but im still not getting anything out of it.

Is there any other components that may have blown also?

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**Author:** ![analogoutput](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/analogoutput/32/29663_2.png) [@analogoutput](https://lookmumnocomputer.discourse.group/u/analogoutput)\
**Post date:** [March 5, 2022, 4:06pm UTC](https://lookmumnocomputer.discourse.group/t/simple-ms20-vcf-problem/4737/2 "2022-03-05T16:06:55Z")

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Possibly the transistors, especially the one closest to the 4.7k resistor on Sam’s stripboard layout. If you put 10R resistors in series on your power rails, check those too.

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**Author:** ![Pat.bayle](https://avatars.discourse-cdn.com/v4/letter/p/9dc877/32.png) [@Pat.bayle](https://lookmumnocomputer.discourse.group/u/Pat.bayle)\
**Post date:** [March 5, 2022, 4:43pm UTC](https://lookmumnocomputer.discourse.group/t/simple-ms20-vcf-problem/4737/3 "2022-03-05T16:43:45Z")

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It works! Turns out i got the wires wrong on the output jack as well. I really shouldnt do these projects with a hangover Haha

What is strange though when i put a square wave oscillator into it. It seems to clip out when the resonance is only slightly turned up.

Is the square wave just too loud for it?

Ramp and triangle work fine.

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<div class="post-metadata">

**Author:** ![analogoutput](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/analogoutput/32/29663_2.png) [@analogoutput](https://lookmumnocomputer.discourse.group/u/analogoutput)\
**Post date:** [March 5, 2022, 6:15pm UTC](https://lookmumnocomputer.discourse.group/t/simple-ms20-vcf-problem/4737/4 "2022-03-05T18:15:14Z")

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> [@Pat.bayle](#):
>
> Is the square wave just too loud for it?

Possibly. This kind of filter sometimes benefits from attenuating the input.

[Especially if it’s the LMNC VCO, or any 3340 based VCO that doesn’t rescale the outputs; then the different waveforms have different amplitudes, and the square wave is the biggest one.]

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**Author:** ![Dud](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/dud/32/610_2.png) [@Dud](https://lookmumnocomputer.discourse.group/u/Dud)\
**Post date:** [March 5, 2022, 11:07pm UTC](https://lookmumnocomputer.discourse.group/t/simple-ms20-vcf-problem/4737/5 "2022-03-05T23:07:22Z")

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Yes adding an attenuator pot on the input works well and also allows you to be able to adjust the “drive” in some way the power of the resonance on the output rendering