For decades, the voltage controlled slew limiter has been a staple of modular synthesisers. With its extreme versatility, it can be used to slew control voltages (CVs), create envelopes, as a low-frequency or audio oscillator and much more.

Today, Contour 1 brings a fresh approach to this classic circuit. It delivers much improved performance and control by incorporating modern design techniques.

At its most basic, a slew limiter slows down the rate of voltage change in a signal. On Contour 1, the rising and falling rates can be individually set using sliders and CV modulation.

The gate and trigger inputs allow the module to be used as a function generator: create snappy attack-release (AR) and attack-decay (AD) envelopes, with slope times ranging from 500 µs to 30 seconds. The dedicated gate input makes it easy to generate +10 V envelopes from any signal source. Using the large tactile push button, AD envelopes can be manually triggered. A trigger will also reset the output voltage.

When set to loop mode, Contour 1 will continually re-trigger itself. In this mode, it fulfils the role of a variable-shape low-frequency oscillator (LFO) or temperature-stable voltage controlled oscillator (VCO) in the audio range.

Both the rising and falling slopes can be individually bent, from concave through linear to convex. While doing so, the deviation in slope time, and thus oscillation frequency, is kept to a minimum. Since the bend parameters are separately voltage controllable, boundless modulation possibilities present themselves.

Explore anything from shape-shifting envelopes to rich VCO timbres: Contour 1 will make you re-think what a slew limiter can do.