# J and S Curves

Several of the DHE Modules apply a curved transfer function to produce their output. The transfer function comes in two shapes:

*Stage*
and
*Booster Stage*
can generate J-shaped envelope stages.
In addition,
*Booster Stage*
can generate S-shaped stages.

*Swave*
can apply a J- or S-shaped transfer function
to shape its input.

*Tapers*
can apply a J- or S-shaped taper
to the position of its *LEVEL* knob.

Each module has a knob that determines the sign (positive or negative) and magnitude of the curvature. Positive curvature creates a J or S shape. Negative curvature inverts the shape. Extreme curvature (positive or negative) creates a curve so sharp as to be nearly square.

Each transfer function (J or S, positive or negative)
is produced by
Dino Dini’s beautiful
**normalized tunable sigmoid function**.

## J Curves

### Positive J Curves

Rotating the *CURVE* knob
clockwise from the center
*pushes the steep part of the curve to the right.*

**Note:**
Extreme positive curvature
makes the curve almost
square at the end.

### Negative J Curves

Rotating the *CURVE* knob
counterclockwise from the center
*pushes the steep part of the curve to the left.*

— |

**Notes:**

- Each curve actually starts at the same voltage. But as the curvature becomes more negative, the rise is so fast that the Scope can’t display the initial value.
- With the knob fully counterclockwise, the rise is so fast that the Scope can’t show it at all. That’s why there’s no image.
- Extreme positive curvature makes the curve almost square at the start. Given that there’s no image, you’ll have to trust me about this. Or try it yourself.

## S Curves

### Positive S Curves

Rotating the *CURVE* knob
clockwise from the center
*steepens the middle of the S curve.*

**Note:**
Extreme positive curvature
makes the curve almost
square just before and after the middle.

### Negative S Curves

Rotating the *CURVE* knob
counterclockwise from the center
*flattens the middle of the S curve.*

**Notes:**

- Extreme negative curvature makes the curve almost square at both ends.
- Each curve actually starts at the same voltage. But as the curvature becomes more negative, the rise is so fast that the Scope can’t display the initial value.
- With the knob fully counterclockwise, the rise is so fast that the Scope can’t show the initial rise at all.