MS20 VCF Schematic

Hi everyone! So I was looking for the schematic of the MS20 HPF/LPF but I only found stripboard layout unfortunately. So if someone has a schematic version of it, it would be really sweet :slight_smile:
I also heard you can add a band pass filter but I didn’t find anything about it :confused:

Well if no one made it already I will do it myself and share it there for everyone :blush:

Was talking about this one:

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I am only aware of the strip board version of this particular design.

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Here is the original schem, so uses a CA3080 instead of a 13700

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It’s a simplified version of René Schmitz’s MS20 filter.
Just take the full schematics and trace over it with a highlighter what you find on the stripboard layout.
Everything else has been left out…
If there is something on the layout not on the schematics, you’re on your own… just add it to the schematics and see if it makes sense.
You can find the full schematics here :

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Well that’s what I was going to do :sweat_smile:
Thank you for the advice

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Oh yeah by the way I heard that the CA3080 and the LM13700 were different and needs some adaptions like few resistors and all… That’s why people sometimes have a very low volume at the output.

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The 3080 is less tolerant of higher input levels than its various successors are, generally starting to distort with input levels exceeding 100mv. That’s why 3080-based circuits attenuate the signal before the OTA and then attempt to restore level afterwards.

Bottom line: if a circuit is deliberately using a 3080 for its distortion characteristics, then subbing a 13600/700 or even a 3280 for it may not yield the same sonic result. But if the purpose is getting a clean signal from the OTA, then a 13x00 shouldn’t be an issue. It certainly hasn’t impeded Electro-Harmonix.

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Okay so I guess it’s okay for the filter circuit :sweat_smile:

I finally made it so if anyone wants it, there we go:

WARN: I didn’t test it yet so do it at your own risk

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Any differences here might be accidental, if the chip’s designer is to be believed (link):

At the time we were considering second sourcing the 3080 anyway.
Also at this very same time, the 16pin plastic dip package had just been developed.
So the development spec for the LM13600 was that it needed a schematic to train someone in IC layout. It needed to have 16 pins. And we were going to layout the 3080 anyway. The schematic part was easy. Just used the 3080 exactly.

Also, the LM13700 starts to distort way below 100 mV:

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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.

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cool, good work! :slight_smile:

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is that tested? Cheers

Rob

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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.

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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:

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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.

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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.

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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

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