Slew Rate Detector?

Is there a module that outputs a CV in proportion to the slope or slew rate of the input CV? i.e. A slew detector?

I can do it with a short delay and a subtractor but is there a single module that will do thismore conveniently?

Sounds like you need a mapper?

ShapeMaster in CV trigger mode can smoothly convert any input voltage to any output voltage you want.

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Not sure what you mean. You want to measure the angle of the CV signal in realtime? To achieve what goal?

Maybe you mean a slope detector that will not simply give true or false (high/low) but a positive or negative number indicating the angle in degrees or similar? Example of a regular slope detector below.

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If all else fails, there’s Formula?

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This discussion might be of interest, seems like you want a rate of change indicator, or first derivative.

They suggest you can accomplish this with a highpass filter, seems worth a try:


Elaborating on my assumption that you want to measure the angle of a CV signal…

I don’t know of a module that does this. So…as mentioned before you could use Frank Buss Formula (or Stochastic Telegraph BASICally) to do the math.

To calculate such an angle, you need at least 2 observations. Since we’re talking about comparing the amplitude of points in time to get either the absolute or relative difference or some ratio.

To get the difference in time you can either buffer the first observation or introduce a delay.

To create a delay you can just introduce a “detour” via an extra cable for the second observation. That would introduce a 1 sample delay.

There are several options to create some other number of samples delay. E.g.

BaconMusic SampleDelay

Another option is a general precision delay. E.g.

Sckitam WaveguideDelay

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Let’s say the answer is 22.3 degrees, what will you do with this information ?

Indeed…to what end? Aso assuming that our interpretation of the question is correct.

As an analyst I know it is pretty common for people to mix up means and ends, problem and solution. In many cases people focus on moving towards their perception of a specific solution, without or instead of actually first describing/defining the problem they want to solve. And consequently find out what the solution space is. And finally pick the solution that solves the problem best.


Knowledge without application has no value.

Your example of 22.3 degrees , for now, is in the same category as the (in)famous 42, in The Hitchhiker’s Guide to the Galaxy by Douglas Adams’s_Guide_to_the_Galaxy#Answer_to_the_Ultimate_Question_of_Life,_the_Universe,_and_Everything_(42)

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I think the OP wants to simply scale the slew rate / slope. In which case any scale module will work.

In any case, what if the slew rate is non-linear?

Scale as in quantize?


Without additional feedback from the OP about the “problem” to solve we can’t really get to any fitting “solution”.

Just my two cents…

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How I understand it is that he wants to “output a CV proportional to a slope or slew rate”, so it could just be that he means scaled or offset. Who knows?

But I enjoyed reading your solution to finding the angle of a slope.

Thanks everyone. Several interesting alternatives to explore.

My goal is to sample and hold a randomly fluctuating voltage, for example from Caudal but I want to sample it and trigger notes at closer intervals when it’s changing faster. So I need something like a CV based on the absolute value of the first derivative of the input. Does this make sense? know this will be infinite for a step signal but it’s OK to clip it to some finite value.

Frank Buss Formula looks promising.

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So can’t you just run the signal from Caudal through a VCA? If you set it to 10% it will scale a 0-10V signal to 0-1V or 1 octave. Or did you have something different in mind?

I want to sample and hold the signal so it’s steady while each note is playing, and with the notes coming faster when the signal is changing faster. I actually don’t know how it will sound or whether it will be pleasant. It’s just an experiment. :slight_smile:

How’s this ?

Actually using Quantum like that is what started me on this exploration.

Here is another variation using a different


Vary the clock rate into Flux, the Speed of Quantum and the Response to Slope Detector to adjust the note speed and density.

I like the result but am looking for more control and possibly non quantized notes.

Actually I’m still a VCV novice but find myself drawn into explorations like this…

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Maybe this?

When you connect a CV source (e.g. Caudal) to a high pass filter (or a DC filter), it will give you a signal that follows the accelleration of the source, like an envelope follower with damping. The amount of “damping” is controlled by the cutoff frequency of the highpass filter. More towards zero Hz, it will pass through more slow voltages, resulting in a longer decay of the envelope.

Connect this “highpassed envelope” to a fullwave rectifier and the rectified signal to a FM input of a square LFO/clock and use this as a gate/trigger for a S&H: The clock/samplerate of the S&H will now follow the CV source. The higher the FM signal, the faster the LFO will go. Play with the tuning of the base frequency of the LFO to adjust the result: the higher the sample rate, the more “smooth” the signal will be.

EDIT: I am not at my computer right now, so cannot show you an example patch, sorry :slight_smile:

In words the patch would be:

CV → HPF → RECT (fullwave) → LFO (FM) → S&H (clock)

Variables/fine tuning are in: Cutoff frequency HPF, Scaling of the HPF signal, Amount of FM to LFO, Base frequency (offset) of LFO

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here is a quick example. you can of course use any source :smiley:


Nice!! Very clever. Works great. Thanks!

I’ll see what patches I can make with this and share any interesting results.