# The Xycloid Module

Xycloid traces a fixed point on the edge a circle rolling along the inside or outside of another circle.

The resulting two-dimensional shape generates a pair of complex, evolving, pulsing LFO signals.

See:

# Controls

• SPEED: The throb cycle frequency.

• RATIO: The number of wobble cycles per throb cycle.

Note: With the IN / OUT switch in the center position, the RATIO knob determines both the rate and direction in which the wobble angle advances. Clockwise rotation advances the wobble angle in the same direction as the throb angle. Counterclockwise rotation advances the wobble angle in the opposite direction.

• FREE / LOCK: Determines whether to round the RATIO value to the nearest integer.

LOCK rounds the RATIO value to the nearest integer, causing Xycloid’s pattern of accents to repeat on every throb cycle.

FREE allows non-integer RATIO values, which lets the accents vary from one throb cycle to the next.

• DEPTH: The dominance of the wobble cycle in the output signals.

• IN / OUT: Determines the direction in which the wobble angle advances compared to the throb angle.

IN advances the wobble angle in the same direction as the throb angle. This produces “inward” nodes when the X and Y signals are plotted on an X/Y graph.

OUT advances the wobble angle in the opposite direction from the throb angle. This produces “outward” nodes when the X and Y signals are plotted on an X/Y graph.

With this switch in the center position the RATIO knob determines the direction in which the wobble angle advances.

• PHASE: Offsets the phase of the wobble angle.

This has the effect of shifting the accents produced when the wobble and throb cycles peak.

# Ports

• X OUT and Y OUT: The output signals.

The polarity switch (UNI / BI) selects the voltage range of the associated output signal. 0 to 10V (UNI) or -5 to 5V (BI).

The GAIN knob applies gain (from 0 to 2) to the signal.

Xycloid selects the range before applying the gain.

• CV: A control voltage signal to modulate the associated parameter. Some CV signals have attenuverters.

# Using Xycloid

• Adjust the SPEED knob to control the frequency of the throb cycle, and therefore the frequency of the overall pattern.
• Adjust the RATIO knob to control the number of wobble cycles within each throb cycle.
• Adjust the DEPTH knob to control whether the throb cycle, the wobble cycle, or neither cycle dominates the overall pattern
• Adjust the PHASE knob to shift the position of the wobbles within the throb cycle, which determines where the accents fall within each throb.
• FIXED mode produces a whole number of wobbles for each throb. As a result, the pattern of accents repeats exactly from one throb cycle to the next.
• FREE mode allows the pattern of wobbles to drift over time. This can create yet another, longer cycle in the pattern of accents.
• For extra chaos, modulate Xycloid’s controls.
• For extra, extra chaos, use Xycloid’s outputs to modulate its own controls.

Xycloid’s X and Y outputs are always similar, but never identical to each other. You can use relationship to create interesting interactions between parameters:

• Modulate two closely related parameters.
• Modulate two parameters that have nothing to do with each other.
• Modulate the same parameter on different modules.

# Plotting Xycloid

When plotted on a two-dimensional graph, Xycloid’s X and Y signals produce a visually pleasing shape, which can be either a hypotrochoid or an epitrochoid.

To view the shape that Xycloid produces, connect its X and Y outputs to a Scope’s X and Y inputs. Set the scope to X x Y mode. Note that the scope’s X/Y mode can also be interesting.