Is there a quick way to know cv range for an input?


I am pretty new. So a couple of noob questions.

Sometimes it’s quite hard to find out what is the accepted range for a particular input. For example, what is the input range for the wavetable position cv for this VCV Library - Erica Synths Black WaveTable VCO? There seem to be no manual. Or what’s the range for modulating various parameters on this one VCV Library - Valley Plateau?

So, is there a way to find a particular input modulation range within VCV rack itself?

And one more related question. Once I know that range what is the best way to adjust LFO output range to cover it? For example, how to convert -5V - +5V lfo output to -0V - + 8V on the LEVEL cv input for Plaits?

If there’s no manual, then trial and error really :). A scope can help a lot to see what is going on. As can Stoermelder’s uMap module (CV to midi converter) which actually moves the knobs physically based on the incoming CV so you can more easily see what effect the CV is having.

A scaling and offset utility like Bogaudio Offset, And again a scope will help you find the right scaling and offset to apply.

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A scope can help a lot to see what is going on.

Wait, how can I use scope to measure accepted input range?

As can Stoermelder’s uMap module (CV to midi converter)

I’ve heard about that one. But it doesn’t seem to exists for VCV rack 2. At least it’s not showing up in the search results VCV Library Any alternatives?

You can’t - but in a trial and error scenario it can help you see what CV is being sent to the input, and what the corresponding effect on the output is. So just try it and see. You can’t break anything :slight_smile:

It’s not in the v2 library yet and there’s no alternative. But you can download a beta build for your platform from here - just drop the .vcvplugin file into your plugins folder and restart rack.

Ye, that’s what I’m doing. But it’s a bit hard to get it by ear if my modulation goes through all of the wavetable positions with BlackWaveTableVCO or maybe it’s from 20% to 80%.

I will, thanks.

That module is a clone of hardware, and there is a two page manual for that

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That’s where the scope can help - put both the CV and the output of the VCO into the scope. If the waveform from the VCO stops changing even though the CV still is, it probably means you have maxed out the CV range. Dial back (or offset) the CV until it starts changing again.


In this case it might help. But it was just an example. It’s not that easy to judge by the scope if modulation does its thing at full range with the Plateau reverb for example. And as far as I understand CV modulation doesn’t have to line up with the corresponding knob - sometimes you can modulate more (or less) with the CV input than with the knob. I was hoping that some kind of general interface for querying those ranges exists.

it doesn’t unfortunately. So you have to rely on your eyes (the scope) and your ears (what sounds good).

This is sadly my main concern with VCV and it’s modules. There are a few modules, that have the accepted input voltage and it’s interaction with the knob value in their manual, but not many. BOGaudio is a very good starting point, they are a really great collection of modules to dive deeper into VCV and the manual is actually usable.

Just as a heads up, to know what to look for:

  • Value needs a bipolar modulation (-xV to +xV) and the value set on the knob corresponds to 0V on the input and modulates to whatever the range interpretation on the modulation input is (mostly +/- 5V).
  • Value needs a bipolar modulation (-xV to +xV) and the value set on the knob is ignored.
  • Value needs a unipolar modulation (0V to xV) and the value set on the knob is 0V and modulates from there further up (mostly 0-10V, but there are modules that interprets a step as 1V or even weirder - try figuring out the switching points of a ML Sequential Switch for example)
  • Value needs a unipolar modulation (0V to xV) and the value set on the knob is ignored (submarine for example).

A good way to figure something out is as already mentioned the scope and 8Vert. Here I am testing a crossover from submarine, where one input is -10V and the other +10V - then I apply a voltage (-4V in the example) on the modulation input and check for the result on the scope. This results in +/- 5V, when set to bipolar.

It’s true that -5…5 vs 0…10 is always going to be a problem, but ignoring the knob just seems kind of dumb, isn’t it? Or am I missing something.

It seems like the world is slowly moving to attenuverters for most CV inputs. Even Fundamental has them now!

With attenuverters it think it’s pretty much

final value = knob + suitableTaperFunction(attenuverter -1 to 1) * CV-input;

Seems weird to turn off the know when a CV is patched.

I actually really like it that way, when there is no attenuator on a bipolar input, because you just have to get your modulation input right and don’t have to care about the knob too. Worst case inputs for me are attenuverted bipolar inputs, where you always have to check if you are not clipping on one side and have to decide if you want to really use a bipolar signal or set the knob to zero and hope that a unipolar 0-10V input will get you the full range…

I’ve always kinda wished knobs would animate natively. It would have been so helpful when starting out.

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There was an easy to use module in 1.1.6

Perhaps it will be ported to 2.x

Rack 2.0 · Issue #83 · Miserlou/RJModules · GitHub

RJModules/Range.cpp at 2dfb636a60ad151b3cbe636eed7a3fc2883cae65 · Miserlou/RJModules · GitHub

Adding: Completely forgot about this module

VCV Library - Count Modula Voltage Scaler

Some modules, like the mind meld, and maybe the frozen wasteland, show where the final cv is with a ring inside the knob. Good feature.


Yes, super handy. Even something like that built in would be fantastic. Any visualisation is good.

Only some of my modules ignore the knob when you connect a CV. but I have tried to ensure that the light on a knob is always extinguished if its being ignored. The XF cross faders ignore the knob, because either the full range of the knob makes sense, OR the full range of the CV makes sense for a cross fader. But uses cases for mixing the two on a crossfader are pretty rare.

(should have been a reply to thread not to you David… :smiley: )
in many of my module
I have dual displays
the RED one representing the main knob, and draggable positional

  • the cv input + the vca (attenuverter) for the cv input
    and a secondary display, representing the COMPUTED and UTILIZED internally values

(example metaAArdavark, BitShifter, ClockabelDelay, and the faboulous RAEL ! :smiley: I love it <3 )