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Dale Emery edited this page Mar 23, 2018 · 33 revisions

NOTE: This wiki describes version 0.5.0 of DHE Modules. For information about the latest version, see https://dhemery.github.io/DHE-Modules/.

Stage is a chainable, single-stage envelope generator with shape control.

See:

Stage User Interface

Knobs

  • LEVEL sets the ending voltage for the envelope segment. The range is 0 to 10 volts.

  • SHAPE sets the shape of the segment. See Technical Details: The Shape Knob.

    The center position produces a linear stage.

    Clockwise and counterclockwise positions produce stages with curved shapes.

    Turning the knob clockwise decreases the initial slope of the envelope stage, yielding a shape similar to an exponential decay curve. Turning the knob counterclockwise increases the initial slope of the envelope stage, yielding a shape similar to a logarithmic decay curve.

    If that seems backward to you, think of the knob as pushing the steep part of the curve left or right.

    At extreme positions, the initial slope is very, very shallow (clockwise) or very, very steep (counterclockwise).

    See some example shapes below.

  • DURATION sets the duration of the envelope segment. The range is 0.001 to 10 seconds, with a duration of approximately 1 second at the center position.

Input Ports

  • DEFER (gate): When the DEFER gate is high, Stage defers to its input by emitting the voltage at the IN port, regardless of other settings.

  • TRIG (trigger): A TRIG pulse starts the segment, beginning with the current IN port voltage.

  • IN (voltage): An incoming envelope signal.

    As of v0.5.0 beta 4, Stage does not limit the IN signal in any way. If you send in four million volts, Stage will send out four million volts. (And yet the parrot will not VOOM.)

Output Ports

  • ACTIVE (gate): Indicates that this Stage is either generating an unfinished envelope segment or deferring to its input.

  • EOC (trigger): Emits a short 10 volt pulse each time this Stage completes a segment.

  • OUT (voltage): The envelope signal produced by this Stage.

Technical Details: The Shape Knob

Stage applies this normalized, tunable sigmoid curve function to shape its envelope stages:

Sigmoid Curve

where x is the current phase of an underlying sawtooth oscillator, and k is the curvature, determined (in a non-linear way) by the SHAPE knob.

In particular, Stage applies the upper right quadrant of the sigmoid curve, which I discovered on the delightful and useful Desmos.com graphing calculator.

Example Shapes

Turning the SHAPE knob moderately clockwise produces a moderately shallow initial slope:

CW Rising CW Falling

Turning the SHAPE knob moderately counterclockwise produces a moderately steep initial slope:

CCW Rising CCW Falling

Turning the SHAPE knob extremely clockwise produces an extremely shallow initial slope:

Extreme CW Rising Extreme CW Falling

Turning the SHAPE knob extremely counterclockwise produces an extremely steep initial slope:

Extreme CCW Rising Extreme CCW Falling

Note that even these "extreme" curves are not at the very ends of the knob's rotation. At the very ends of the rotation, the slope at either the start or the end of the stage is so steep that I can't get a screenshot of it. The scope can't display it properly. You can see a little of the difficulty in the bottom right image. The actual peak is at 10 volts, like the highest value in all of these images, but the scope shows it peaking at approximately 8 volts.

Technical Details: States and Events

At any time, Stage can be one of four states, each defined by what it emits at its OUT port.

  • HOLDING: Emits a fixed voltage, called the hold voltage.
  • GENERATING: Generates and emits an envelope according by the DURATION, LEVEL, and CURVE knobs.
  • LEVELING: Emits the voltage of the LEVEL knob.
  • DEFERRING: Emits the voltage of the IN port. That is, Stage defers to its input.

When Stage starts, it sets its hold voltage to 0.0 volts and begins HOLDING.

Holding

When HOLDING:

  • Stage emits its current hold voltage.
  • All knobs are ignored.
  • The IN port is ignored.
  • If the TRIG port is triggered, Stage begins GENERATING, starting an envelope at the current IN voltage.
  • If the DEFER gate goes high, Stage begins DEFERRING.

Generating

When GENERATING:

  • Stage emits an envelope that approaches the voltage set by the LEVEL knob, along a shape set by the SHAPE knob, over a duration set by the DURATION knob.
  • Changes at the DURATION, SHAPE, and LEVEL knobs affect the envelope as it progresses.
  • If the envelope reaches its end, Stage emits a pulse at its EOC (End of Cycle) port and begins LEVELING.
  • If the TRIG port is triggered, Stage restarts the envelope at the current IN voltage and continues GENERATING.
  • If the DEFER gate goes high, Stage terminates the envelope and begins DEFERRING. No EOC pulse is emitted.

Leveling

When LEVELING:

  • Stage emits the value of the LEVEL knob.
  • If the TRIG port is triggered, Stage begins GENERATING, starting an envelope at the current IN voltage.
  • If the DEFER gate goes high, Stage begins DEFERRING.

Deferring

When DEFERRING:

  • Stage emits the voltage at its IN port.
  • The TRIG port is ignored.
  • All knobs are ignored.
  • If the DEFER gate goes low, Stage sets its hold voltage to the current IN port voltage and begins HOLDING.
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