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Morphing filter antiquities
MUFF WIGGLER Forum Index -> Eurorack Modules  
Author Morphing filter antiquities
Dcramer
Long before the Emu Digital morphing filter was released into Euroland, Dieter Doepfer concocted analog design:
The A-107 Morphing Type Filter is said to be based on the Obie Expander filter set, also used in the A-106-6

The A-107 version is much slicker in that it allows you to chain together a sequence of filter types made up of its over 30 different filter shapes, you can control the morph time between sequence steps (this is voltage controllable) and either step through the sequence or CV through it.
Voltage controlled resonance and a built in VCA round out the package.

It should be painfully obvious to all who know Me that I purchased it because it looks so cool love

I didn't find much info online and there aren't much demos either.

Some complained that they disliked the basic timbre of the filter as well.
I'd wanted to do an audio demo of all the filter types but as soon as I started patching I was caught up in a lurvely huge washy drone.

The filter can run very clean, making it perfect for filtering chordal oscilations.

If you want to hear it's character, I posted a very long track made up of a crossfading mixture of "every fackin Oscs in da house" all patched through the A-107 as it slowly morphs thru almost all of its filter types:

https://www.muffwiggler.com/forum/viewtopic.php?t=189654

This is fun! This is fun! This is fun!
sauflesautres
Maybe it's old but i still want one and a A-113.

Oberheim ? Do you mean Rossum (Emu) ?

Can the morph can happen without any external modulation ? Or does the filter need lfos or clock pulses to morph ?
Dcramer
Yes, Rossum (I couldn't remember the sp! d'oh! )
You can manually morph it by simply choosing another filter with the morph time set high but for auto morphing you need to have a minimum 2 step sequence.
I experimented with just that and you can get very subtle, almost Additive sounding, filter envelopes by morphing from one shape to another (or several) all triggered by a note start. thumbs up
sauflesautres
I've taken a listen to the audio you posted but haven't taken the time to listen carefully enough yet.

Some more noob questions about the A-107. I've read the manual but i'm unsure if i understand correctly...

So if one programs a 4 step filter chain in the A-107, you can set the morph time and it will morph from each step to the other without any external lfo or clock ?

When i first got into eurorack i didn't realize how Doepfer has cool designs. The A-107 definitely seems unique and useful.
Dcramer
Yeah there's tons of threads up here about amazing Doepfer designs.
A cool thing that you'll notice about Doepfer is that he designs several modules to be used together to experiment with a previous electronic circuit or instrument design. Like his Trautonium modules or vocoder modules.

Yup, the A-107 lets you set a morph time and that's the amount of time it takes to move from one filter shape to the next one in sequence.
But the morphing time can also be voltage controlled so if you wanted to speed up or slow down the external sequence clock, you can alter the morph time to ensure that your completing the morph fast enough.
I think there's something like 36 filter shapes woah and a sequence can have 32 steps, so one sequence can use almost all the shapes.

Which is exactly what takes place in the piece I posted; I believe it cycles through 32 filter shapes twice with a morph time of almost a minute! MY ASS IS BLEEDING
Dr. Sketch-n-Etch
I originally had similar ambitions for the Polaris, but it didn't come to pass.
L.C.O.
Dr. Sketch-n-Etch wrote:
I originally had similar ambitions for the Polaris, but it didn't come to pass.


So kind of a low pass situation, you are saying?

But seriously: I like Polaris quite a bit, but imagining morph function in it is exciting.

Also: note to self: gotta play with long morph times in Rossum filter.
sauflesautres
Dcramer wrote:
Yeah there's tons of threads up here about amazing Doepfer designs.
A cool thing that you'll notice about Doepfer is that he designs several modules to be used together to experiment with a previous electronic circuit or instrument design. Like his Trautonium modules or vocoder modules.

Yup, the A-107 lets you set a morph time and that's the amount of time it takes to move from one filter shape to the next one in sequence.
But the morphing time can also be voltage controlled so if you wanted to speed up or slow down the external sequence clock, you can alter the morph time to ensure that your completing the morph fast enough.
I think there's something like 36 filter shapes woah and a sequence can have 32 steps, so one sequence can use almost all the shapes.

Which is exactly what takes place in the piece I posted; I believe it cycles through 32 filter shapes twice with a morph time of almost a minute! MY ASS IS BLEEDING

Thanks for all the explanations DCramer! Really interesting.

Whenever i see a thread about Doepfer popping up, i try to read it. And since buying a few Doepfer modules recently, i was amazed at the quality of them... Those Trautonium modules are fascinating, especially the A-113 which i seem to love the sound of online demos.

Do you happen to know if the A-107 sound is similar to the A-106-6 (Xpander filter) ?

Here's something i quite liked with an A-113 and A-107 : http://www.youtube.com/watch?v=vt_TxMLAH8w
Dcramer
Dr. Sketch-n-Etch wrote:
I originally had similar ambitions for the Polaris, but it didn't come to pass.

woah waah
sauflesautres
Dr. Sketch-n-Etch wrote:
I originally had similar ambitions for the Polaris, but it didn't come to pass.


This would have been amazing but it would have probably put the Polaris in my "one day i'll get one" list instead of being the 2nd filter i bought since price and hp would probably be much higher.

Still one of my all-time favorite filters.
Dcramer
Yup, Polaris sounds awesome, I may need a second for stereo!
Imagine the Polaris with a CV in that simply crossfaded across all the filter types! woah
Don't despair tho, the quick elegant way to patch it up is with a MI Frames:
Split your signal to four different filters, patch those four to the Frames I put, patch the Frames mix out to your vca. Then simply setup the crossfaded keyframes and one incoming CV will perform your crossfade! w00t
tuj
Ja, I got a 107. All the Doepfer haters can step off. Dieter's designs are simple, sometimes more cost-effective than I'd like (thinking quality of op-amps) but his designs are very good and he does some thing that no one else does. Is there another theremin module out there?

Anyway, yeah the 107 is a beast of a filter. The resonance is quite strong, and the combo BP/notch filters you won't really find in analogue-land like Dieter's.

Then you have clocking it, which is also brilliant.
natureclubcassettes
Dcramer wrote:
Yup, Polaris sounds awesome, I may need a second for stereo!
Imagine the Polaris with a CV in that simply crossfaded across all the filter types! woah
Don't despair tho, the quick elegant way to patch it up is with a MI Frames:
Split your signal to four different filters, patch those four to the Frames I put, patch the Frames mix out to your vca. Then simply setup the crossfaded keyframes and one incoming CV will perform your crossfade! w00t


Wow, thanks for the epic track posted in your link. It almost reminds me of using a slow LFO to scan a polyphonic drone on the AX-60, which has a super weird filter response curve.

I'm not sure using 4 filters in a patch for a single voice is necessarily elegant, though. At most I've had 3 at a time (A-108, A-124 and MMG). Only use the MMG currently, and I'd bet there's a lot of others out there without a bunch of filters in their racks due to Mutable modules. This could also (sort-of) be accomplished with something like a FXDf sent to Linix with a Quadra sending envelopes. I know it lacks the cool CV control for each filter type, though...

hmm... maybe MMG with frequency being cv'd into FXDf and then so on.... with tons of delay and stereo action after
Dcramer
Certainly, there's all kinds of cool variations and ways to get this without having to buy a wall full of modules! This is fun!

I've got lots of filters, so when I did the track, my heart ached as I dearly wanted to patch the entire thing through the Lurvly Korgasmatron set to highpass. Guinness ftw! Guinness ftw!

Would've been a killer sonic addition, but I stuck to my plan of just featuring the A-107.

Yes Sauf! The A-106-6 should sound like the A-107, which simply has more shapes available. thumbs up
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