Descrete SEM VCF (VCF1 3521EFM)

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vladosh
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Descrete SEM VCF (VCF1 3521EFM)

Post by vladosh » Sun Apr 04, 2021 8:48 am

Has anyone built any of these descrete VCF's from EFM ,schematics are at fonitronik's site http://www.modular.fonik.de/Page37.html
just made a pcb layout for one of these - VCF1 3521 ,replaced the transistors with BCM847/857 ,this is very small parts count SEM type VCF using transistors instead of CA3080/LM13700 ,the pcb is suitable for 4U format
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ynynyyn.jpg
etetetetettte.jpg
CF 3521 Double Sided.JPG

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oldenjon
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Re: Descrete SEM VCF (VCF1 3521EFM)

Post by oldenjon » Sun Apr 04, 2021 11:31 am

Looks like a fun project. The discrete OTAs are basically the same ones in the Manhattan SVVCF and many people have gotten that working. IIRC that filter has a design flaw and is not actually state variable though. There's also a recent thread about a discrete OTA filter here in the DIY forum. Can't remember if it was state variable or 4 pole.
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emmaker
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Re: Descrete SEM VCF (VCF1 3521EFM)

Post by emmaker » Sun Apr 04, 2021 2:54 pm

The EFM stuff aren't the greatest circuits out there.

They are pretty basic and usually functional but not high end circuits.

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vladosh
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Re: Descrete SEM VCF (VCF1 3521EFM)

Post by vladosh » Sun Apr 04, 2021 3:51 pm

the first vcf i ever got working was a simple LM13700 SEM type VCF by EFM and i loved it ,i don't mind circuit being simple

Ayab
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Re: Descrete SEM VCF (VCF1 3521EFM)

Post by Ayab » Mon Apr 05, 2021 1:58 pm

Thank you vladosh great work. A discrete filter design looks good and am especially interested in HPF at the moment. Will build one of these.

My first attempt at a double sided was a failure but this looks more manageable and will hopefully get my confidence back.

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vladosh
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Re: Descrete SEM VCF (VCF1 3521EFM)

Post by vladosh » Mon Apr 05, 2021 4:04 pm

i posted a single layer layout at electro-music ,but it has quite a few jumpers if you don't mind ,however i have not built this yet i just made the layout

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Re: Descrete SEM VCF (VCF1 3521EFM)

Post by Ayab » Fri Apr 09, 2021 12:11 pm

Thank you so much that single sided over on E-M (great forum for diy) is even better for me. I will chop the top 1/4 off to do a eurorack sized sandwich. Looking forward to the famous discrete SEM filter sounds!

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vladosh
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Re: Descrete SEM VCF (VCF1 3521EFM)

Post by vladosh » Fri Apr 09, 2021 3:26 pm

good luck with it ,please share if it sounds good

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