The Slope module is a voltage controlled slew limiter and modulation source. The core idea behind this module comes form the classic Serge Dual Universal Slope Generator, which has in turn inspired many popular modules including the Makenoise Maths and and the Befaco Rampage. This is version 2 of my adaptation of the module; the original version is available here as circuit diagram. This version comes as a proper PCB and front panel set, featuring a single slope generator in an 8 hp eurorack module. At the modules' heart is a voltage controlled slew limiter, whose output is a copy of the input voltage except with any sharp steps replaced by smooth ramps, with a rate set by the front panel Rise and Fall controls as well as the corresponding control voltages. When used on pitch CV, the slew limiter creates a glide effect.
Additional logic circuitry turns the Slope into a versatile modulation source. By feeding a signal to the Gate, the module becomes a voltage controlled envelope generator, with the attack time set by Rise, an optional Sustain phase, and the decay time by Fall.
About the circuit
Internally several improvements were made to the circuit. The configuration of the slew limiter core has been changed from inverting to a non-inverting unity-gain amplifier. This ensures very accurate tracking (0.01% gain error) between the input and output voltage, so pitch control voltage can be processed by the unit without tuning errors. Accurate gain is further preserved by a high 1M input impedance to avoid loading down the voltage source, and a low-impedance output to drive the subsequent stage accurately.
The logic circuit has been improved to provide well-defined end-of rise (EOR) and end-of-cycle (EOC) gate outputs, which open up gate delay and pulse timing functions, as well as complex cycling when multiple modules are used together. The gate outputs are driven by push-pull comparators, so they can both source and sink current and will trigger nearly any module properly.
Finally all outputs have status LEDs to show what is going on visually; the main output LED is bicolor.