MS20 VCF Schematic

Tom “Electric Druid” Wiltshire has some thoughts on the LM13700 and distortion. There are optional linearization diodes but Tom opts to bypass them in his design and thus attenuates the input signal to 50-60mV pp in order to limit distortion to levels that sound good to him. You’d need to attenuate more if you don’t want the distortion characteristic to be a feature of your VCF.


cool, good work! :slight_smile:


is that tested? Cheers


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If this is tested / untested do mark the image accordingly. There are enough schematics around that are incomplete or contain mistakes etc.


I replied just below :slight_smile:

I don’t know since i didn’t test it yet, but it matches exactly with the Schmitbitz schematic. I took the time to check if every components were connected exactly the same way and I found 0 mistakes between the schematic and the stripboard. Then I just added the switch part! I will test it anyway soon for a project I will keep you posted :slight_smile:


Ok, then please mark it as ‘UNTESTED’ in the mean time. Search engines will not read this thread, they will just publish the picture with whatever status it has.


The schematic is “tested”. @lu.caas has checked that it matches the verified stripboard layout. You can’t really do anything more than that to “test” it.


I just modified the text, I’m sorry! I should have think about it

Yeah I know. Anyway I’ll tell you in the future if it works or not! I’ll let it as I verified for now


I tested it and IT WORKS !!


Just running through the schematic @lu.caas posted and getting a bit confused with the IC connections. When I look at say, the TL074, it appears to have the 4k7 resistor and 4.7nF cap connected on pin 14 per the stripboard layout. In the schematic they are connected to pin 1. Likewise, the stripboard layout shows the input jack connecting via a 10k resistor to pin 4 on the LM13700 whereas the schematic gives pin 13.

Am I looking at this right? I’m new to all of this so apologies if the answer is obvious :slight_smile:

The TL074 is symmetric, four identical op amps connected to pins 1–3, 5–7, 8–10, 12–14. I don’t know why the schematic shows a different assignment of op amps to functions but functionally it’s the same.

Likewise it looks like the two OTAs in the LM13700 are switched around but again the two are identical so it doesn’t matter.

For consistency with the stripboard just renumber the pins on the schematic:

  • TL074 pin n → pin (15–n) (except pins 4, 11)
  • LM13700 pin n → pin (17–n) (except pins 6, 11)

and I think it’ll be correct. (But someone should verify this.)

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how do the designs actually differ? where do we find the look mum no computer layouts?

LMNC layout is shown above

of course it is, i am grateful for that but do we have a library or folder or github or somewhere with collected layouts or something? and / or is there some additional explanation about this particular layout refering to where it comes from and why it is as it is? and / or how it works?

Ah of course, that makes perfect sense. Good to have it noted here for anyone going through it. Thanks for clarifying that :slight_smile:

You can find links here

amazing! such an abundance of resources <3 love that! but the MS-20 project is not featured there…