Serge Dual Slope Generator – Model 1240

The 1240 DSG is the ultimate patch-programmable control voltage generator. A Serge Slope Generator is a slew limited unity gain voltage follower whose positive and negative slew rates are voltage controllable. It has an extremely wide range covering sub-sonic to high audio rates. Trigger inputs and pulse / gate outputs extend the slewing functions for use as a voltage controlled (VC) LFO, envelope generator and a variable pulse delay mono-stable functions.

One VC responds roughly exponentially, and two additional VC inputs are routed to individual Rise and Fall slope attenuverters for maximum flexibility and convenience. This newly updated circuit now includes temperature compensation to help eliminate drifting. The linearity and accuracy of the slews allow them to be used for exacting applications such as portamento functions.

The 1240 has two identical slope generators (A & B) – each of which can be set to self-trigger (Loop), or even to trigger each other for some wild modulation and audio effects. It also has two auxiliary outputs which provide an output that is the greater of A & B (PEAK), and another that is the lesser of A & B (TROUGH). These are interesting and go far beyond normal summing / mixing.

Inputs (x2)

IN – Unity gain CV / Signal input
TRIG IN – Trigger or Gate begins Rise / Fall cycle
RISE / FALL CV INs – Controls rise & fall slopes, respectively. Attenuverted.
1V/OCT – Exponential CV input (limited accuracy)

Outputs

OUT+ (x2) – Tracks IN CV signal (Unipolar)
OUT+/- (x2) – Tracks IN CV signal (Bipolar)
FALL GATE (x2) – Goes high during fall phase
END GATE (x2) – Goes high at end of fall phase
PEAK – Outputs the greater of slopes A and B
TROUGH – Outputs the lesser of slopes A and B

Features

Among the many functions the 1240 DSG can perform are (x2):

VC Transient / Envelope Generator – simply started by trigger or gate at TRIG IN.
VC LFO – The rates are controlled by the Rise and Fall Rate knobs and inputs, and the slopes controlled from LOG thru Linear to Exponential.
VC Timing Pulse / Gate generator.
VC Portamento with separate controls for rise and fall rates, and slopes.
Envelope Follower (Detector) – The VC decay rate allows the response to be moved from positive to negative peak detection.
VC Pulse Delay (Monostable).
Sub-Harmonic Series Generator. A trapezoidal wave-shape is generated for sonorous, smooth sounds.
Audio Generator with variable symmetry and a range into kilohertz regions.
Non-Linear Low-Pass Filter. The VC slew limiting can progressively turn a sawtooth wave into a triangle and many variations between. Thus a slope generator can be used as a very interesting low-fidelity VCF.
VC Clock divider
VC Trigger/Gate width processor
AR, ASR Envelope Generator

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