Ken Stones - CGS (Cat Girl Synth)
Synthesiser Module Kits

Now proudly supported through ELBY Designs

Sub Oscillator Use this twin sub-oscillator with one or two VCOs for fat sounding lead or harmonies, or with a VCO and an LFO for harmonic sequences, or as a pattern based sequencer
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Psycho LFO This is a bizarre little LFO that produces a wide range of pseudo random effects from random timed stepped, to smooth flowing
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DC Mixer

Mix synthesizer level audio signals or control voltages with this d.c. coupled mixer.
Joystick Controller using the CGS04
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Burst Generator A rhythm and timing accessory that generates a burst of gate or trigger pulses at various speeds. Used for washboard, maracas or similar rapid-burst percussive effects when connected to the appropriate sound generating device
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Voltage Controlled Divider Use this as a timing accessory for sequencers, or with a VCO for frequency trills like those of the old 8-bit computer games. Unilke other voltage controlled dividers, this one preserves the pulse width of the incoming signal.
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Pedal Board/Mini Keyboard A simple circuit that can be used to make a small monophonic 1 volt per octave keyboard, or pedalboard
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Gated Comparator This module can be used as a simple gate delay, a semi-random melody generator, a comparator, and a gate/clock controlled comparator. All in all, a very versatile module.
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Drum Simulator This module is the embodiment of the classic twin-T circuit in a form that is suitable for connection to modular synthesizers. It contains two separate drum sounds, each individually triggered, as well as something unique - adjustable harmonic content
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Chime Simulator This module contains a pair of two or three tone chimes that are suitable for connection to modular synthesizers. Each chime sound is created by modulating two or three square wave oscillators together, and applying an envelope to the result. Each chime is individually triggered.
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Super Psycho LFO This module is a much expanded version of the Psycho LFO, featuring six free-running oscillators, each variable between LFO and audio ranges, two of which can be switched to have triangular wave outputs. Each oscillator can be switched between low and high ranges, as well as off, and also has a rate LED, to allow visual determination of the frequency at which it is running. As per the original, there are also level and glide controls
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Master Divider The purpose of this module is to divide down a system master clock (e.g. a VCLFO) to drive an array of sequencers or other timed events. The different phase outputs are to allow for modules that may trigger from the falling edge of a wave, or to allow for deliberate lagging of an event. It would for example be possible to have two sequencers running from this unit, one at 1/8 of the frequency of the other, their outputs being mixed to give a sequence that changes fundamental pitch each eight notes.
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Gate to Trigger Converter This module contains a pair of two gate to trigger converters, allowing key-down gate signals, or those from gate sequencers etc. to be converted into a much narrower trigger signal as required by some percussive effects. These may come in handy when adapting various drum sound generators to synthesizer use
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Analog Logic Voltage Processor

This module is the analog implementation of some basic logic elements. Instead of dealing with binary inputs, the "logic" is applied to whatever voltages are present on the inputs. When the AND element is fed several voltages, the output will equal the the lowest input voltage. The NAND output will be the inversion around 0 volts of the AND output. When the OR element is fed several voltages, the output will equal the the highest input voltage. The NOR output will be the inversion around 0 volts of the OR output. Apparently the AND and OR functions are the same thing as "peak" and "trough" on old Serge synthesizers, though they are implemented somewhat differently.
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Sequential Switch A basic switching/sequencing module with many uses.
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Wave Multiplier The idea for this project came from the fabled middle section of the Serge wave multipliers. It could equally be described as a wave folder or a timbre modulator.
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Band Pass Filter A utility bandpass filter for creating artifical instrument resonant cavities etc.
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Digital Noise This module is a very standard pseudo-random digital noise source with a few enhancements. Instead of running a fixed high frequency clock, a VCO is used instead, allowing for unusual sweeps, and for reducing the speed right down to a series of random pulses. The internal linear VCO can also be bypassed so an external source such as a 1V/oct VCO or LFO can be substituted. It has pink and white noise outputs, and two separate (unique) digital outputs for use in triggering other circuits.
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Infinite Melody Maker The name of this module is a play on its function. Put simply, it generates a series of semi-random or themed stepped control voltages, or if you prefer, white and pink control voltages. The pink function is probably better known as 1/f.
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Matrix Mixer -Euro Version The matrix mixer is a four input, multiple output bipolar or unipolar DC coupled mixer, for mixing control voltages or audio signals. In cases where you require several different mixes from a common set of signals, this module is ideal.
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Steiner Synthacon Filter This module is a "tribute" module, based on the awesome Steiner-Parker Synthacon VCF. Those who know me will know I'm not a big VCF fan. Nonetheless, this VCF really appeals to me. Its sound is quite unlike the Moog ladder, and has a lot of character.
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Pulse Divider This module consists of several parts, a pulse divider with integer divisions between 2 and 8, and several logic elements. The divider is used to generate interrelated pulses for use in creating poly-rhythms, and unusual sequences or as a sub-oscillator/sub harmonic generator.

As well as the pulse divider, there are also four boolean logic elements, two inverters an OR gate and an AND gate for the processing of gate and trigger signals

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CV Cluster The C.V. cluster is an unusual kind of mixer. It takes two input voltages - a base control voltage, and a modulating control voltage, and creates the sum and differences of them, as well as a range of voltage in between.
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Sawtooth Pitch Shifter The Saw Pitch Shifter is an experimental combination of op-amp summers and comparators with surprising results, ranging from complex wave shaping to pitch shifting of saw tooth waves.
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Quad Logic Gate The Quad Logic Gate is a very simple module that can be built in one of five flavors : XOR, OR, AND, NOR and NAND. It is a simple way to gain additional control of gate and trigger pulses within a system. It can also be used for some simple signal multiplying. The XOR is well known as a square wave "ring modulator", though interesing effects can also be generated using the other configurations. Each gate has an inbuilt LED to indicate the status of the outputof that gate.
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Modulo Magic A CV and signal processor based on the mathematical modulo principle. Makes a great wave multipler too!
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Diatonic Converter The Diatonic Converter is an adapter for projects such as the Infinite Melody and Gated Comparator, constricting their outputs to the notes of a major or minor diatonic scale instead of the chromatic scale. A single control line selects between major and minor. It can also be used as a stand-alone module when driven from other systhesizer gate events.
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Cascade Mixer The Cascade Mixer is an experimental mixer that can be built in one of several ways - a unity gain cascaded mixer, a binary weighted (or scaled) mixer, or as a staircase generator when coupled with a binary counter.
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Cynare Drum Simulator The Cynare drum simulator is the third in the series of CGS drum simulators. It generates a single drum sound that can be adjusted to sound like a cymbal, hi-hat, snare drum, electronic drum, or numerous other percussive sounds. It is a complete dedicated synthesizer in its own right, including six oscillators, a noise source, a mixer, an envelope generator, a VCF and a VCA.
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VCO This VCO started out life as a replacement for the original VCOs in my '73 Serge, so it replicates a lot of the functionality of that module. Of course there have been numerous enhancements to the design as well, making it right at home in a 1 volt per octave synthesizer.
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Twin Wasp Filter A dual version of the popular CMOS based Wasp VCF, featuring adjustable distortion.
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Weighted Random Switch The weighted random switch is another module for introducing unpredictability into synthesizers. The original requirement was for a circuit that would, upon receiving a clock signal, randomly direct a single input to one of four outputs, but with a twist. Four knobs or control voltages could be used to sway the likelihood of one or more outputs being selected over the others.
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XOR/NXOR Logic This board is an add-on for the Pulse Divider and Boolean Logic module, adding XOR and XNOR funtionality. It can also be used to compare two analog signals, either positive or negative in value.
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Analog Switch Matrix The Analog Switch Matrix is a complex router, allowing one input to be switched between four outputs, or vice versa, or even to route one signal through one of four external effects (e.g. wave multipliers, filters etc.). It can also be used as four independent analog switches.

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Gate Converter The purpose of the Gate Converter is to turn standard positive gate signals into negative to postitive going gate signal. This is particularly handy when interfacing to other manufacturer's modules that require a zero crossing singal to operate. It can also be used to convert assorted LFO or VCO signals to square or rectangular waves, to extract some form of gate signal from an envelope and so on.
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Bi-N-Tic Filter This is a strange mixture of a VCO and a switched capacitor filter based on the filter presented by Jan Hall in Electronotes. If you are after something different, this fits the bill. After all, how many filters have a sync input?
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Utility LFO The Utility LFO is a dual manually controlled LFO offering a number of standard and combined outputs for general low frequency work, such as filter and phaser sweeps, clocking sequencers and so on.
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8-Step Sequencer Serge style programmer/sequencer.
The Programmer/Sequencer is a Serge inpired multi-stage sequencer. Unlike most sequencers, this one makes no use of binary counters. Rather, it uses a set of individual stages, each one directly accessible.
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Stompbox Adaptor This is an external input amplifier with extra provisions so that it can also be used as an effects pedal interface. There are three identical amplifiers on the board.
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Slope Detector The slope detector is an event-driven gate/trigger generating device. It monitors a control voltage, and triggers one of three "gate" output dependent on what the control voltage is doing.
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VCA Voltage Controlled Amplifier, suitable for both audio and control voltage modulation.
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Tube VCA Tube based Voltage Controlled Amplifier / timbral gate. While this module basically operates as a VCA, it does add a degree of distortion to the signal. How much distortion depends on how hard it is driven. Add feedback and it begins to oscillate, syncing to the incoming signal to some extent. All this while running on a standard synthesizer power supply, with no extra heater supply required.
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Active Real Ring Modulator The Real Ring modulator now has buffered inputs and outputs, and a pre-amp stuitable for guitar use
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MOTM Distribution Board MOTM compatible power distribution bus board
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Utility Envelope Generator This is a basic envelope generator of the ADSR variety
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Dual Voltage Processor This module is a variation on the standard two-inverting-stage op-amp DC Mixer. It has provision for an offset pot, four DC mixer inputs, processor style inputs, with both inverting and non-invering outputs, though the inverting output cannot be used with the processor function.
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Gate Sequencer A sequencer designed for controlling pulsed or gated events, for rhythm and percussion.
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PCB Mounting Rail These mounting rails are a convenient way of mounting CGS PCBs behind a Serge style panel
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Trunk Lines/Multiples These boards can be used as cascadable multiples, to create trunk lines between different cabinets, or assuming you have something else that uses the same termination, for expansion/breakout. It uses 16 way ribbon, like used in Euro power, every second wire connected to ground to form a shield between the signal wires. You can mount one of these in each cabinet of a large system, and hook them up from behind with the ribbon. If you hook just two in different cabinets together, you have 8 trunk lines between them, reducing the need for long patch cables. If you place one in each of several cabinets, and run a common ribbon between them, then you have an inter-cabinet bus. If you mount them side by side, and use a common ribbon between them, you have a multiple. As a bonus, the board is designed to work with banana jacks as well, so your bus/trunk lines can go between different types of synths (mini jacks and bananas).
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Pot Mounting Rail This PCB is designed to help mounting and wiring pots or LEDs to panels. It uses the 1 inch horizontal spacing standard of Serge panels, and provides mounting for 16 pots or LEDs.
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Digital Reverb This is a basic reverb module constructed around the Belton BTDR-2H Reverb Module. From a single input, two channels of raw reverb are generated. Mix outputs are also provided, allowing the input/reverb mix to be controlled via a panel pot. An additional feedback function is provided for emphasizing the effect, or even for generating screaming feedback
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Quad Comparator and Memory Cell This module is the combination of a quad comparator "voting system" and memory cell (flip-flop). It can be built in many ways to suit the builder's needs. For example, if the memory cell functions are not required, they can be omitted. Alternatively, the panel presence of the comparators can be greatly reduced if the memory cell is the primary interest.
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Matrix Mixer The matrix mixer is a multiple input, four output bipolar or unipolar DC coupled mixer, for mixing control voltages or audio signals. In cases where you require several different mixes from a common set of signals, this module is ideal. This variant of the matrix mixer is designed for use behind Serge 4U panels.
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LED Driver Board This is a tiny ancillary board that contains a single transistorized LED driver for monitoring synthesizer module outputs.
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Real Ring Modulator This is a pre-assembled classic diode ring modulator for when a four quadrant multiplier simply won't do.
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Low Pass Gate
This module is a variation on the Classic Buchla Low Pass Gate module developed by Peter Grenader and released here as his gift to the Serge DIY community.
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Breadboard/Prototyping Board A 6" x 2" pcb ideal for prototyping your own designs or custom building a module
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CGS SERGE Modules Licensed Serge design

Adaptations of several classic Serge modules.
These designs have been done with the permission and collaboration of Serge Tcherepnin himself.

All designs are produced under license from Serge.

Voltage Controlled Slope
Developed from the Serge DUSG, this is a general purpose version of the VCS made popular by Bananalogue.
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1973 Envelope Generator
This is an adaptation of the original Serge Envelope Generator from the early "R" series PCBs.
This is NOT an ADSR style generator, and can be used as an LFO.
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1973 VCF
This is an adaptation of the original Serge VCF from the early "R" series PCBs.
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Ring Modulator This module is a variation on the 1973 Classic Serge R6 Ring Modulator.
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Negative Slew
This is the Serge Negative Slew which was part of the original line of modules. Ultimately this would go on to be replaced by the Dual Universal Slope Generator. It can be used as a falling sawtooth LFO, VCO, or as the name suggests, a lag/slew for falling voltages. Rising voltages are passed unhindered.
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Positive Slew
This is the Serge Positive Slew which was part of the original line of modules. Ultimately this would go on to be replaced by the Dual Universal Slope Generator. It can be used as a rising sawtooth LFO, VCO, a simple envelope generator or as the name suggests, a lag/slew for rising voltages. Falling voltages are passed unhindered.
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Peak And Trough
This module is a variation on the 1973 Classic Serge Peak and Trough module. It is much like the Analog Logic Voltage processor, though a little less precise. It is presented here for those who want to build themselves a classic Serge.
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Triple Wave Shaper
This module is a variation on the 1973 Classic Serge Triple Wave Shaper. This design started off as a wave shaper for the original Serge VCO, and has persisted as an available module since that time.
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Touch Responsive Keyboard
This module is a variation of the Touch Responsive Keyboard published in the January/February 1977 issue of Synapse magazine.
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Programmer Sequencer
This is a redesigned circuit board for the CGS59 Programmer/Sequencer. Unlike that version, this one has no panel-format specific PCBs. The column boards have been replaced with boards that contain 8 stages. These can be used to drive pots or switches in any panel configuration you wish.
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Triple Bi-Directional Router
The Triple Bi-Directional Router is a group of three switches each of which can route one input to either of two outputs, or either of two inputs to one output according to a pulse or control voltage level. It can also be assembled to sequentially route one input to one of four outputs, or one of four inputs to one output.
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Phaser and Audio Mixers
This module is a variation on the classic Serge Phaser module. On the PCB are also two AC coupled audio mixers.
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Smooth And Stepped Generator
The Serge Smooth and Stepped Function Generator (SSG) is s a complex multi-functional module to provide various slew and sample functions.
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Triple Comparator
The TRIPLE COMPARATOR consists of three independent functions which are useful in the production of square waves and variable pulse waves. The Comparator reference level can be a time-varying control voltage, a complex audio signal, or a fixed preset voltage. Additionally, the comparators are useful for level detection and for logic decisions based on amplitude. The module also contains a single, non-adjustable, Schmitt trigger
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Noise Source
The Serge noise module can be built in several ways. In it's simplest form, it contains three basic outputs, White noise, Pink noise, and a random voltage suitable for use with Sample and Hold modules. An optional Sample and Hold circuit is included on the PCB. Alternatively, the basic version may be coupled with the CGS92 Serge Smooth and Stepped Generator to make the Random Voltage Generator module.
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Dual Channel Stereo Mixer
This module is a variation of the Serge Dual Channel Stereo Mixer, built using the CGS101 Quad VCA and the CGS101 Equal Power Panner drivers.
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Equal Power Panner
Serge Equal Power Panner driver.
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Voltage Controlled Gain Cell
This is an adaptation of the original gain cell used in many of Serge's later designs.
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Voltage Controlled Resonance Filter
The VARIABLE Q VCF (VCFQ) is an excellent general-purpose VCF offering simultaneous low-pass, high-pass, band-pass and notch (band-reject) outputs. The resonance (Q) of this filter is dynamically variable by manual or voltage control.
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Wave Multipliers
This is an adaptation of the original Serge VCM containing three distinct sections for the addition of harmonics to a signal.
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Dual Universal Slope Generator
This is an adaptation of the original Serge DUSG, on which the CGS75 Voltage Controlled Slope is based.
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Extended ADSR
This is an adaptation of the original Serge Extended ADSR (voltage controlled).
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Resonant Equalizer
The RESONANT EQUALIZER (EQ) is a unique ten-band filter designed specifically for electronic sound synthesis and processing. Except for the top and bottom frequency bands, all other bands are spaced at an interval of a major seventh. This non-standard spacing avoids the very common effect of an accentuated resonance in one key, as will be the effect from graphic equalizers with octave or third-octave spacing between bands. Spacing by octaves will reinforce a regular overtone structure for one musical key, thereby producing regularly spaced formants accenting a particular tonality. The Resonant Equalizer's band spacing are much more interesting, producing formant peaks and valleys that are similar to those in acoustic instument sounds.
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Best of CGS

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Copyright 2000. All rights reserved.     Revised: June 5, 2017