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 Forum index » Clavia Nord Modular » NM Classic (NM1 or G1)
Newbie Question:nonlinear controllers
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Tusker



Joined: Feb 03, 2005
Posts: 110
Location: Texas

PostPosted: Wed Feb 09, 2005 1:23 pm    Post subject: Newbie Question:nonlinear controllers Reply with quote  Mark this post and the followings unread

I'm trying to figure out how create non-linear controllers for some patches. For example:

Let's say we have three oscillators tuned to different harmonics.

As a controller is applied (say modulation) I'd like the first oscillator to to decline sharply at about 1 third of the travel and the 2nd harmonic to increase sharply. As the controller moves about 2/3rd of it's travel, Id like the 2nd harmonic to decline sharply and the 3rd harmonic to increase sharply.

Is there a way for me to do this kind of non-linearity with the controllers? Thinking back to my forgotten algebra, I think they are simply -ve quadratic equations with varying constants. Any advice?

Thanks,

Jerry
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Blue Hell
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Joined: Apr 03, 2004
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PostPosted: Wed Feb 09, 2005 1:32 pm    Post subject: Reply with quote  Mark this post and the followings unread

It might be easier to construct something with envelopes and logic delays to make one envelope trigger after the other. Maybe use multi-stage envelopes.

Or even with sequencer modules (with some smoothing applied over the outputs), sequencers are not very expensive on the NM Classic.

Jan.
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Kassen
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Joined: Jul 06, 2004
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PostPosted: Wed Feb 09, 2005 2:57 pm    Post subject: Reply with quote  Mark this post and the followings unread

Wave shaping.

Seriously. The first and most obvious thing is to create custom velocity curves by aplying a overdrive to your velocity signal but this same principle can be aplied to more complex questions like yours too.

You start with the first parameter and figure out what the curve looks like if you map you modulation signal to that. Then you use amps, waveshapers and the like to build this curve. You may need to add in some compare values and logic modules if there are especially complex curves involved like you apear to need but the basics remain the same. If this is hard then the combination of a saw wave as input and a scope may help but most of the time it can be done by ear. In your case you need two or three of those constructions which will output to different modules and that simply take the same input (modulation wheel in your case).

You dont specify wether a realy smooth curve is important to you but if it isn´t then perhaps defining three or four states and crossfading between those controled by some controler might do and this might be much cheaper and faster.

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Kassen
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davep



Joined: Jul 05, 2004
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PostPosted: Wed Feb 09, 2005 11:04 pm    Post subject: Reply with quote  Mark this post and the followings unread

The audio Shaper module is great for creating nonlinear control signal curves. Also, the seldom-used Kybd Vel Scaler module. You can also use the clipper module combined with an amp module to make a control signal reach the "end" level faster at one destination relative to another destination.

If you want to do more unusual things to your control signals, try the wavewrapper or even a resonant filter set to a very low cutoff frequency with high resonance.

When setting up this type of circuit, it can be helpful to substitute a simple Constant module knob for the control signal so you can easily hear how the signal is acting as you turn the knob.

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Tusker



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PostPosted: Thu Feb 10, 2005 5:16 am    Post subject: Reply with quote  Mark this post and the followings unread

That's fantastic, guys. Thank you. Lots of options to try. When you mentioned waveshaping and filters, I was going duh. It's perfect. A standard waveshaper will get me 99% of the way there and the rest will be playing with the intercepts and constants. Good idea about using a constant signal to test the arrangement. Thanks.

There is one idea I'm thinking of putting in the G2 wish list, and that is a tracking generator. A tracking generator is a map (in the Oberheim Matrix 12 for example) which takes a control signal and plots it against a user defined response curve on a cartesian grid. Why would this be helpful?

The G1 and G2 have rectifiers and shapers, but it would be very cumbersome to develop a full complement of graphical shapes in this manner. A math module (algebra based) would be easier, but it won't work for certain curves (and certain users). I can think of two interface choices for this module. One would be the ability to actually draw a graph and have the G2 memorize it. Drawing tools (curves, straight lines, triangle waves, square waves) would make it easier. Yet another interface, is to have the ability to insert shaping components into a pre-existing x=y graph. Components similar to shelving eq, parametric eqs, etc, would be placeable anywhere on the graph. These objects would morph the graphs from an x=y starting point, to the shape desired by the user.

The outcome is a very generalized shaping tool for all kinds of signals. Should I post this idea? (Newbie nervousness.)

Thx,

Jerry
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Blue Hell
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PostPosted: Thu Feb 10, 2005 6:12 am    Post subject: Reply with quote  Mark this post and the followings unread

Tusker wrote:

The outcome is a very generalized shaping tool for all kinds of signals. Should I post this idea? (Newbie nervousness.)


Yes please do, note that a comparable idea - lookup tables - was discussed in a keyboard scaling related thread in the wish list, the graphical user interface you suggest would make it more "general purpose" Ithough.

Jan.
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Kassen
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PostPosted: Thu Feb 10, 2005 6:45 am    Post subject: Reply with quote  Mark this post and the followings unread

Tusker wrote:
There is one idea I'm thinking of putting in the G2 wish list, and that is a tracking generator. A tracking generator is a map (in the Oberheim Matrix 12 for example) which takes a control signal and plots it against a user defined response curve on a cartesian grid.


Good thinking.

I hope, I´ve been thinking the same :¬)

You shouldn´t be nervous about posting ideas. I think you are very much on the right track with your thoughts here and with questions like this nobody will think less of you. Sure others asked them before, sure many of them already made up answers but I don´t think anybody has yet come up with *THE* answer so your attempt is as valid as any.

Parameter mapping is a realy profound question and IMHO one of the largest and most important questions in electronic music at the moment.

The very worst that could happen is that you made a little reasoning mistake somewhere and that somebody will point that out, saving you time and effort. Please, please, relax, you are amongst friends.

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Kassen
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egw



Joined: Feb 01, 2003
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PostPosted: Thu Feb 10, 2005 8:05 am    Post subject: Reply with quote  Mark this post and the followings unread

I think you could make a tracking generator out of the control sequencer.
With some math to normalize the input signal.
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jamos



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PostPosted: Thu Feb 10, 2005 8:20 am    Post subject: Reply with quote  Mark this post and the followings unread

(irrelevant comment, deleted)
Last edited by jamos on Thu Feb 10, 2005 9:41 am; edited 1 time in total
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Kassen
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PostPosted: Thu Feb 10, 2005 8:48 am    Post subject: Reply with quote  Mark this post and the followings unread

egw wrote:
I think you could make a tracking generator out of the control sequencer.
With some math to normalize the input signal.


On the Classic? for the G2 I fully agree but looking at the board I do think this is a question about the classic which complicates matters considderably.

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davep



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PostPosted: Thu Feb 10, 2005 2:35 pm    Post subject: Reply with quote  Mark this post and the followings unread

Tusker wrote:


There is one idea I'm thinking of putting in the G2 wish list, and that is a tracking generator. A tracking generator is a map (in the Oberheim Matrix 12 for example) which takes a control signal and plots it against a user defined response curve on a cartesian grid.


Check it out - You can use the G2 X-MUX module as a tracking generator. If you connect a set of Constant modules to the eight inputs, and set them to multiples of 16 (#1=0, #2=16, #3=32, #4=48, etc.) the MUX output will equal the control input. Now when you start messin' with the levels of the Constant modules, you get the tracking generator. Works exactly the same as the Oberheim module except is has eight positions instead of only four. And you get the added feature of the variable crossfade control, which allows you to get a quantized effect if you don't crossfade. Cool, huh?

And we're getting off the original topic here, but just FYI you can also use the X-MUX as a lo-fi complex audio waveshaper by substituting an audio input for the control input.....

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Dave Peck
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Tusker



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PostPosted: Thu Feb 10, 2005 10:11 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hey, that's great. Didn't pick that up on my scan of the G2 modules. It does look like the G2 sequencer will do these kind of things (linear multi-segments) in a way that the G1 can't.

Thanks,

Jerry
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cebec



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PostPosted: Fri Feb 11, 2005 1:42 pm    Post subject: Reply with quote  Mark this post and the followings unread

Dave, can you post an example of both of these when you have a chance, please?
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davep



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PostPosted: Sat Feb 12, 2005 2:33 pm    Post subject: Reply with quote  Mark this post and the followings unread

cebec wrote:
Dave, can you post an example of both of these when you have a chance, please?


I'm posting examples of using the X-Mux as a tracking generator and as a lo-fi waveshaper over in the new "G2 Building Blocks" subforum. Enjoy!

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