CVA-7 CV Analyzer

Product Info

CVA-7 is a free rack extension for Reason, the music DAW produced by Propellerhead Software. This 2U utility lets you analyze a CV signal in various ways. It can also act as a CV Spider Splitter on steroids (converts the input signal into an inverse, unipolar or bipolar signal).

Main features

  • Analyze and interpret an incoming CV signal with graph, keyboard and numeric displays
  • Freeze time for detailed analysis
  • Easily convert an incoming signal into its inverse, unipolar or bipolar version (up to 4 outputs)
  • Use AUX OUT CVs for controlling other devices in a creative way

Front

CVA-7 (Front)

Folded Front

CVA-7 (Folded Front)

Back

CVA-7 (Back)

Features

CV Analyzer (graph)

CV Analyzer (graph)
  • The main LCD screen displays the CV signal live as a graph
  • Zoom in and out to see more details (from real time to 30s)
  • Freeze the display for detailed analysis by clicking directly in the scrollbar or on the screen itself
  • Use the LIVE VIEW toggle to resume or stop live view
  • Use the GRAPH toggle to turn the screen on or off
  • Use the COLOR button to switch between 5 different colors
When the raw CV value is outside the range defined by the SCALE knob, clipping is shown in red. It doesn't mean the signal itself is clipping, it just means that it extends beyond the graphics display's current height. Use the SCALE knob to bring the whole signal into view.
Graph Clipping

CV Analyzer (keyboard)

CV Analyzer (keyboard)
  • Interpret the incoming CV signal as a note or a gate
  • Use the   toggle to turn the keyboard on or off
These values show how the CV signal will be interpreted when sent to a NOTE or GATE input respectively

CV Analyzer (numeric)

CV Analyzer (numeric)
  • Display the incoming CV signal as an integer, a percentage or a raw value (accurate to 5 digits)
  • Keeps track of min and max value (with manual or automatic reset)
When zooming out, the CV value shows an average of the values displayed by a single dot on the screen. In order to get an accurate reading for a single CV value, make sure you are zoomed in completely (ZOOM knob all the way to the right).

CV OUT

  • CV IN is sent to 4 independent CV OUT sockets
  • Those sockets are independent on the state of the device (LIVE VIEW, ZOOM, SCALE, etc...)
  • Each socket can convert the input signal in the following fashion:
CV INCV OUT
Original PASSTHROUGH Passthrough Result
Original INVERSE Inverse Result
Original UNIPOLAR Unipolar Result
Original BIPOLAR Bipolar Result
Setting UNIPOLAR or BIPOLAR simply instructs the device to convert CV IN using the corresponding formula. The device does not detect whether the incoming signal is unipolar or bipolar in the first place. As a result, if CV IN is a bipolar signal and CV OUT is set to BIPOLAR the result will be a doubled/offsetted signal.
Bipolar Twice

AUX OUT

AUX OUT
  • 3 CVs sockets whose output match exactly the content of CV, MIN and MAX on the front of the device
  • Unlike CV OUT, the value of these sockets depend on the state of the LIVE VIEW, ZOOM, and SCALE controls
  • Coupled with automation, these sockets (CV in particular), allow for some interesting and creative results. In this short clip,AUX OUT on the top device is connected to CV IN on the bottom one.
AUX OUT in action

A few words about CV

As stated in the Reason operation manual, "CV signals are typically used to modulate parameter values and do not carry audio". Internally, a CV signal is represented by a floating point number which can range between -10000.0 and +10000.0. In practice, the vast majority of devices use the range between -1.0 and +1.0.

2 critical concepts to understand

  • When a device receives a CV value (a floating point number between -10000.0 and +10000.0) it needs to interpret it to give it meaning
  • The somewhat familiar representation of CV as an integer number between -127 and +127 is an interpretation of the [-1.0, +1.0] range: everything outside this range is simply clamped at the extreme values

How does CVA-7 interpret CV?

For numeric display (CV, MIN and MAX):
  • In RAW mode, there is no interpretation: the value is displayed as it is received (with a precision of 6 digits total), shows the full range ([-10000.0, +10000.0]) and as a result is the only accurate version of the signal
  • In % (percent) mode, the signal is first truncated to the [-1.0, +1.0] range, then scaled to an integer value in the [-100, +100] range
  • In INT (integer) mode, the signal is first truncated to the [-1.0, +1.0] range, then scaled to an integer value in the [-127, +127] range. This is the default mode, which corresponds to the most common CV use.

Confused?

Since INT is clamped and RAW isn't, you may encounter situations that seem confusing. For example, a RAW value of 64.0 will be represented by 127 in INT mode, because +1.0 and above (like 64.0) is represented by 127. The good news is that the vast majority of all CV signals are in the range [-1.0, +1.0].
RAW To INT Mapping
For keyboard display (including NOTE and GATE):
  • For the NOTE representation, the signal is truncated to the [0.0, +1.0] range and is interpreted as a midi note using a standard formula as defined by Propellerhead. As a result, it is expected that every device should interpret a note signal in the same fashion, hence resulting in the same pitch!
  • For the GATE representation, the signal is truncated to the [0.0, +1.0] range and scaled to an integer value in the [0, +127] range.
For graph display:
  • When the SCALE knob is all the way to the right (default) the signal is converted to a pixel in the range [-1.0, +1.0] and if it exceeds the range it is represented as a red clipping line.
  • Turning the SCALE knob adjusts the clipping range thus effectively allowing to show the full signal and get rid of the clipping lines

Automation & Mapping

Automation
  • Most parameters can be automated like any other control in Reason. In order to automate the red selection dot (Graph Select) or the scrollbar (Graph Scroll), you will need to add a track for the device and select the corresponding option in the automation menu as shown in the above screenshot
  • Most parameters can be remotely controlled like any other control in Reason. In order to remote map the red selection dot (Graph Select) or the scrollbar (Graph Scroll), you will need to use the top menu "Options/Remote Override Edit Mode" and select the appropriate arrow in the LCD screen

Tips & Tricks

Pausing several CVA-7 devices at the same time

It is quite common to analyze a CV signal both before and after it goes through some device (for instance, to check whether the device transform the signal the way you expect it to). The usual setup is to add a CVA-7 before the device, and another after the device.

In this case, it is most convenient to pause both instances of CVA-7 at the exact same time, to check one single value for example. Here is how you could do it:

  • Make sure all concerned devices are inside a Combinator
  • Open the Combinator's programmer, and for each CVA-7 instance, set one button to LIVE VIEW (you must choose the same Combinator's button for each CVA-7, for instance, if you choose to use Button 1, click on the first CVA-7 in the Programmer and set Button 1 to LIVE VIEW, click on the second CVA-7 and set Button 1 to LIVE VIEW as well)
Tip 1 Example
This same technique can be used for ZOOM, SCALE, and all other automatable controls (use the Combinator's rotaries for CVA-7's knobs). You can use Graph Select to control the red dot and Graph Scroll to control the position of the scrollbar.

Technical details

This section can be skipped and is of interest only if you care about some of the internal details of implementation.

Intepretation formulas

  • For RAW mode
    out = in;
  • For % mode
    temp1 = clamp(in, -1.0, +1.0);
    temp2 = sign(in) * ceil(((abs(temp1) * 101) - 1) / 2);
    out = clamp(temp2, -100, +100);
  • For INT mode
    temp1 = clamp(in, -1.0, +1.0);
    temp2 = sign(in) * ceil(((abs(temp1) * 128) - 1) / 2);
    out = clamp(temp2, -127, +127);
  • For NOTE
    out = floor(clamp(in * 127 + 0.1, 0, 127));
  • For GATE
    temp1 = clamp(in, 0, +1.0);
    temp2 = sign(in) * ceil(((abs(temp1) * 128) - 1) / 2);
    out = clamp(temp2, 0, +127);

CV OUT formulas

  • For PASSTHROUGH mode
    out = in;
  • For INVERSE mode
    out = -in;
  • For UNIPOLAR mode
    out = (in / 2.0) + 0.5;
  • For BIPOLAR mode
    out = (in * 2.0) - 1.0; // clamped to [-10000, 10000]

Thanks

  • A big thanks to Clayton Miller (Twitter @presteign) for the design and look & feel of the rack extension.
  • A big thanks to all the beta testers from the ReasonTalk forum who helped shape the final product. In particular I wanted to call out WongoTheSane, challism and Loque.

Release Notes

1.0.0 - 2016/11/30

  • First release.