Red Control (or CV-1)

Quantizer (used with TKB) (QTKB)
The QUANTIZER (QUAN) provides a simple means to turn any control voltage into voltage steps corresponding to well tuned (equal-tempered) tones of the musical scale. It is scaled to 1 volt per octave. Thus, a zero to +5 volt envelope at the Quantizer's input produces a staircase of voltages corresponding to a chromatic scale spanning five octaves.

If patched to the 1 volt per octave input of an oscillator tuned to “E”, a gradual slope of 1 volt applied to the input of the Quantizer will produce the following steps of the musical scales:

E-F-F#-G-G#-A-A#-B-C-C#-D-D#-E
(normal chromatic scale)

If the 1/6 Scale Select is HIGH, then the scale produced will be:

E-F#-G#-A#-C-D-E
(whole-tone scale)

If the 1/3 Scale select is HIGH, then the scale produced will be:

E-G#-C-E
(scale of major third steps)

If both the 1/6 and 1/3 inputs are high, the scale will be:

E-F-G#-A-C-C#-E
(alternating half-step/minor third step)

Since the Scale Select inputs can be activated very quickly, the Quantizer can produce a very wide variety of tonal effects, quickly moving between four different types of musical scales (chromatic, whole-tone, the augmented triad, and a six-step major-minor scale often heard in certain oriental [sic] musics).

The basic Quantizer features seven or eight channels, depending on the model. Available as a “stand-alone” module, the Quantizer has seven channels and takes up two inches of panel space. Other models are available, however, with some of the channels “hard-wired” to provide quantized outputs for other Serge modules such as the various Sequencer Programmers and the Touch Keyboard... Accuracy of the Quantizer is 3 cents maximum deviation from the ideal equal-tempered semi-tone over a five octave range (i.e. just about the limits of pitch sensitivity of the human ear). Response time for all channels is about 8 milliseconds.

Dual Analog Shift Register w/ input attenuator pot (2ASR)
The ANALOG SHIFT REGISTER (ASR) is a sequential sample and hold module for producing arabesque-like forms in musical space (see diagram). Whenever pulsed, the previously held voltage is sent down the line to three consecutive outputs to produce the electrical equivalent of a canonic musical structure. A pulse output permits linking two or more Analog Shift Registers together to form longer patterns. The DUAL ANALOG SHIFT REGISTER (2ASR) is available for high-density systems.

Dual Transient Generator (DTG)
The DUAL TRANSIENT GENERATOR (DTG) provides two independent outputs with voltage controllable rise and fall times. This module is identical to the Dual Universal Slope Generator except that it does not have all of the front panel features. This module is a useful, space-effective unit to be used for many of the same functions as the Dual Universal Slope Generator. Common uses of the Dual Transient Generator are for simple “AR”-type envelope generation, as a dual voltage-controlled low frequency oscillator, or as a voltage-controlled clock (especially suitable for clocking the Touch Keyboard Sequencer or any of the Sequencer Programmers). These functions can be patched with the Dual Universal Slope Generator, but since many of the features are left unused in these patches, the Dual Transient Generator provides the same function while using less front Panel space.

Random Source (RS)
[The RANDOM VOLTAGE GENERATOR (RVG) produces random voltages which vary smoothly or in a step-wise manner. Random timing pulses are also available. Rate of change of all outputs is voltage controllable over a wide range.] The RANDOM SOURCE (RS) allies a Noise source with a Random Voltage Generator in one single module.

Smooth / Stepped Generator (SSG)
The SMOOTH & STEPPED FUNCTION GENERATOR (SSG) is a complex multi-functional module to provide various slew and sample functions.

• The Smooth section will place a positive and negative slew (glide) on a changing input voltage for lag effects, voltage controlled portamento, and non-linear, low frequency filtering. With the CYCLE jack patched to the input, the unit will oscillate yielding a voltage controlled triangle wave LFO. A high level into the HOLD input will hold the current output level, whether the unit is oscillating or processing an external control voltage. This is identical to a track-and-hold function. 
• The Stepped function can be used as a sample-and-hold with voltage controlled slew rate limiting. Slew rate limiting limits the size of the step at the output. For example, with a random voltage input and the step size set to a small value, the output is a random voltage that varies only slightly from step to step, gradually covering the entire range of the input voltage. No large changes in the output will be allowed. With the Cycle jack patched to the input and a trigger applied to the Sample input, complex staircase waveforms are generated. 
• The COUPLER is an internal comparator comparing the Smooth and the Stepped outputs. This is useful for generating complex control voltages and for patching a random voltage generator. In fact, the Random Voltage Generator module is a Smooth & Stepped Generator internally patched to function exclusively as such. If random voltages are often used, a Random Voltage Generator is a more space-efficient module; but if seldom used, the Smooth & Stepped Generator can be patched when needed (and can be used for other functions when not used as a random voltage generator). Note that a Noise Source is needed for use of the Smooth & Stepped Generator as a random voltage generator. 

Control Voltage Processor (PRO)
Control modules are essential and they can be categorized as two types:

1. Programmable controls which can happen automatically according to other voltage controls and to manual settings. 
2. Controllers which are used as performance devices. 

The automatic controls can be as simple as a low frequency oscillator to produce vibrato or slowly moving cyclic changes, or can be very complex. The Touch Activated Keyboard Sequencer, all of the Sequencing Programmers, and the Pitch and Envelope Follower provide powerful performance interfaces between the performer and the instrument(s), and many others can be used. Pressure controllers, joysticks, foot-pedals, electronic keyboards, and other sophisticated controllers such as light sensors computers and microprocessors are easily connected to the Serge system.

Control voltage processors add another dimension to patches in the analog synthesizer. The Smooth and Stepped Function Generator, the Dual Universal Slope Generator, the Dual Comparator, the Analog Shift Register, the Active Processor, and the Quantizer further extend the hierarchy of sound synthesis and control, and along with some of our specialized audio processors, these sophisticated modules enable synthesis of the highest order.

Dual Universal Slope Generator (DSG)
The DUAL UNIVERSAL SLOPE Generator (DSG) is the ultimate patch-programmable control voltage generator in the Serge system. At least one (DSG) is recommended for almost every Serge system. and in most cases, a number of these are desirable. People familiar with our previous series of “slewing” modules know about the importance of this kind of function in a large patchable synthesizer system. For those unfamiliar, it is advised that the various applications as outlined here and in the Serge Owner's Manual are studied. The uses of this module are numerous, some duplicating functions found on other synthesizers, some totally unique to the Serge system. Most systems require a number of control voltage generators to control the various signal processors and modifiers. Sources of trigger, pulses (clocks), control voltage processors (portamento's), regular repeating voltages (LFO's) are standard synthesizer requirements. The Dual Slope Generator is the main module providing these functions in the Serge system.

The Universal Slope Generators are unity gain voltage followers with voltage controllable slopes. The range of control is exponential, extremely wide, and the Rise and Fall times can be controlled independently. The range of the Slope Generator is from sub-sonic to high audio frequency. Trigger inputs and trigger outputs allows each section of this dual module to function as a transient (envelope) generator, pulse delay, or in a “cycling mode” (to produce an LFO or clock). Since the Rise and Fall times are voltage controllable, this adds another dimension to the above functions. Two VC inputs are available, one is calibrated at 1 volt per octave (within about 3%), and the other is fully adjustable in the negative and positive direction. This VC input can control either the positive slope (rise), negative slope (fall), or both. The linearity and accuracy of the slewing amplifiers allows them to be used in the most exacting applications, such as processing the output of a keyboard or sequencer to produce portamento functions. Note that this portamento function has a separate rate control for rising notes and falling notes... An interesting portamento effect. Among the functions which one Slope Generator can be patch-programmed to perform are the following:

• VC Transient Envelope Generator. The envelope is simply started with a trigger, or may be used with a gate input to obtain a steady-state sustain level on the envelope. This envelope will repeat if the END trigger output is connected to the TRIG IN input. 
• VC LFO. Patched as mentioned above, a wide-range, low-cost, space-efficient Low Frequency Oscillator can be patched when needed. The Slope Generator is often used as an LFO since it is more cost effective than a regular oscillator switched to a low frequency range. it has a built-in LED to show its current output level, and it has a synchronized trigger output. The waveform can be set from saw to triangle, and the rising ramp can be voltage controlled independently of the falling ramp. 
• VC Portamento device. The accuracy of these devices makes this portamento function useful with keyboards and for generating control voltages of arbitrary shapes and times with computer control. Analog control of slopes allows the computer to do less “number crunching”, and frees the processor from time-consuming routines that are more easily handled in this low-cost multifunctional hardware. 
• Envelope Follower (Detector). The decay rate is voltage controllable with the unique function that under voltage control, the response may be moved from positive peak detection to negative peak detection. 
• VC Pulse Delay (Monostable). When the unit is triggered, it will produce an envelope set by its Rise and Fall knobs (and VC's) and then the END pulse will go high. This may be used to trigger another Slope Generator, ADSR, or advance a sequencer. 
• Sub-Harmonic Series Generator (Divider). If a series of triggers are applied to the TRIG IN jack that are faster than the total rise plus fall time, then the unit will divide the incoming triggers by a whole number. This allows the user to program synchronized rhythmic relationships (such as 2 against 3, 13 against 11, and so on). If the Slope Generators are set to audio frequencies, and the incoming triggers are in the audio range, then the output will be the sub-harmonic series. This is similar to the “hard sync” sound found in other synthesizers (and is the main reason that it is not included on Serge VCO’s). 
• Audio Oscillator. The range reaches 4000 Hz, and the waveform has variable symmetry (saw to triangle). 
• Non-Linear Audio Processor. The slew limiting is voltage controllable, so a sawtooth wave input will progressively be transformed into a triangle wave. This aspect allows the unit to be used as a low-fidelity VCF! 

Extended ADSR (ADSR)
The EXTENDED ADSR (ADSR) is a complex envelope generator using the four segment envelope normally encountered in keyboard synthesizers. This ADSR, however, is designed with extra features such as voltage control of each section, an initial voltage controllable delay time, switchable slopes, and a master voltage control. Each segment may be manually set and voltage controlled, so the module may be used with or without keyboards as a versatile, programmable control voltage generator. In addition to the normal Attack, Decay, Sustain, and Release segments, an Initial Delay time is included. This allows multiple envelopes to be initiated from a single trigger or gate, delayed with respect to one another. Ramps for the Attack and Release segments can be switched to either linear or exponential slopes with the three-position switch. In the left [i.e. top] position, the Attack will have an exponential slope. In the middle position, both the Attack and Release will have an exponential slope, and in the right [i.e. bottom] position, all will have linear slopes. A master 1V/OCT control will control all slope times to allow such effects as decreasing the entire envelope time as the pitch of an associated oscillator increases. This phenomenon is typical of many acoustic instrument envelopes.