Revenge of the Combinator
Pages: 1, 2, 3, 4

CV Basics, Reason-Style

Many of Reason’s devices have CV outputs on their back panels. (The term “control voltage” is not strictly accurate: True control voltages are found only on analog synthesizers. But that’s what Propellerhead calls Reason’s control signals, so we’ll use their term.) Among the sound-producing modules, only the NN-XT sampler lacks CV outputs. They’re also found on the Matrix Pattern Sequencer, the vocoder, the MClass Compressor, and the Scream distortion effect. Even more Reason devices have CV inputs, usually associated with trimpots (small input level knobs) so that the amount of response to the CV signal can be scaled up or down.

Here’s the back side of the Combinator module on page 1. You can see the four CV inputs and their associated trimpots at left, labeled Rotary 1–4.

CV signal values in Reason can range from –127 to 127. Some of the CV outputs, such as the SubTractor envelopes, are unidirectional (meaning they go from 0 up to 127), while others, such as the SubTractor LFO, are bidirectional (they go from –127 to 127). The Mälstrom modulator outputs can be either uni- or bidirectional, depending on the waveform selected. The trimpots by the CV input jacks reduce the range of an incoming CV, and the Spider CV Merger & Splitter can invert a CV.

Most Reason parameters can be set between 0 and 127. When driven by one or more CVs whose combined total drops below zero, they will “peg” at zero. Conversely, if sent two or more CVs (for instance, using a Spider to merge two signals) that goes higher than 127, the parameter will peg at 127.

To understand CV range a little better, try this experiment:

1. Create a Combinator and create a SubTractor inside it.
2. Connect the SubTractor’s rear-panel LFO 1 output to the Combinator’s rotary 1 CV input:
   
   
   
   
   
3. Reduce the LFO 1 rate to about 16 and select the rising sawtooth waveform for the LFO:
   
   
   
   
   
4. Open the Combinator programmer, select the SubTractor in the device list, and assign rotary 1 to Amp Env Attack in the target column:
   
   
   
   
   

At this point, you’ll see the amp envelope attack slider on the SubTractor rise slowly and smoothly from the bottom of its travel to the top, then snap back to the bottom and start over. Note, however, that the CV coming from the LFO is being affected by three settings—the Rotary 1 rear-panel input trim (which is set to 64 by default), the front-panel setting of the Rotary 1 knob (also 64 by default), and the min/max range defined in the programmer (0–127 by default).

Turn the Rotary 1 front-panel knob down to 0. Now the slider will spend half of its time pegged in the minimum position, rise to the center of its slot, and then snap back to the bottom. This is because half of the time the LFO’s output is below zero. When Rotary 1 is set to 127, the slider does the opposite: It starts in the middle, rises to the top, and then pegs there for a while.

Move Rotary 1 back to 64 and turn the rear-panel trim up to 127. Now the slider pegs briefly at both the top and the bottom. This is because a trim setting of 64 is equivalent to multiplying the input value by 0.5. When the trim is at 64, the ±127 range of the LFO is compressed to ±64. The value of the front-panel Rotary knob is then added to this, causing the CV signal to take on a range of 0–127 (the same as the range of the slider). Try some other experiments with these settings to learn how CV signals are processed.