Designing a diode ladder filter from scratch

hi people,
here’s the latest episode in my filter design series. this time, we’re building a three pole diode ladder filter (though it could be debated if that is indeed the right name … ah semantics). it has nice smooth resonance and is very stable (unlike some other diode-based implementations)! let me know if you have any questions & thanks for watching!

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whey hey Moritz! niceeee.

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Watched this morning! Loving the series!

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Really thank you for sharing this !

I post it also in the thread with the others one :wink:

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Have you a complet schematic for this filter please ?
I often take screenshots but it would be easier :slightly_smiling_face:

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@moritzklein thank you a lot for your great work sharing, this is very helpfull for all the diyer community! I LOVE your tutorials, better serie than Netflix !!
I advise everyone to support him on his patreon page, nice surprises await you !!

Im studing your diode ladder filter version, and it look nice!!

Recently, I have build a 9v version of an diode ladder filter by Tom Gamble which looks pretty much like this one, but with multiple cv and audio inputs !! I like it so ! (I suppose it can be working with 12v too)
Here the schematic:

Source:
http://synthdiy.fonitronik.de/index.php/efm-files

I want to build a other version with a Q cv control (resonance), it look very usefull ! (take a look of VCF-6C by EFM)

My build:

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@moritzklein I have to ask about your “shifts” module. Honestly I don’t even care what it does I just want that LED rainfall :rofl:

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Nice video as always! Makes me wish i didnt sell my korg poly-800 years ago though!

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unfortunately i can’t really draw it by hand (doesn’t really fit on one page). but here’s a complete simulation on falstad: https://tinyurl.com/y7eftwyz

also, here’s how you would mod it to get a resonant bandpass: https://tinyurl.com/y95z6k4m

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mine feels like it’s on its last leg unfortunately – LFO starts modulating things randomly and spontaneously, headphone output has loud ground noise… sad!

it’s basically just 10 4-bit shift registers chained together. i then selected three LEDs where i attached basic gate-to-trigger converters. so the idea is that you can send in bits (either manually via a pushbutton or through an external input) and have those circulate through the registers. every time a bit passes a gate-to-trigger converter it fires. so something like a sample & hold for rhythm! you can also choose if you want it to loop and from where (after the first 4, 8, 12, 16 … bits).

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great looking panel! is that wood?

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Thank you, yes it’s recovery wood, I use a lot of old drawer bottoms or cases of strawberries from the market to build my Hobo synth muaha

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hello m’leader, how’s it hanging?

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Thanks, i made a copy, invert it and re write the value

is it good ?

EDIT : deleted a bad version’s schematic

almost perfect – there is one 22k resistor in there that should be a 33k! also i noticed that for some reason the resonance sounds nicer with a 100k/27k combination instead of the 10k/2k7 in the resonance op amp’s feedback path!

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Thx, ah yes i correted it. (and delete the older one in my previous post)
like this ?

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spot on, looks great!

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I’ve just made a stripboard layout of it

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looks good. proper decoupling & dealt with the unused op amp too! great work!

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