CGS Modules you can build

• CGSLD LED driver
  
  This is a tiny ancillary board that contains a single transistorized LED driver for monitoring synthesizer module outputs.

• CGSRR Real Ring Modulator
  
  This is a pre-assembled classic diode ring modulator for when a four quadrant multiplier simply won't do.

• CGSRRM Real Ring Modem
  
  Someting to try out with your Real Ring Modulators. Two are required.

• Adapter Banana to 3.5mm adapter plug
  Are your Serge and your Euro rack modules not talking? Try this.

• CGS01 Sub-oscillator/harmonic sequencer
  
  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.

• CGS02 Wavetable for VCOs
  Feed this module with a high frequency from a VCO or DCO for a range of selectable waveforms/tones. ROMs are available that contain 4 or 8 banks of eight waveforms per bank.

• CGS03 Psycho LFO
  
  This is a bizarre little LFO that produces a wide range of pseudo random effects from random timed stepped, to smooth flowing. One of my most popular modules.

• CGS04 D.C. Mixer
  
  Mix synthesizer level audio signals or control voltages with this d.c. coupled mixer.

• CGS04 Joystick controller
  
  This module uses a pair of D.C. mixers with a two-axis joystick to control various synthesizer funtions.

• CGS05 Parallel port adapter Mk II
  
  For use with the DCO, D/A converter and Keyboard sacanning sub-modules.

• CGS06 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.

• CGS07 Gate Sequencer (new version)
  
  An expandable sequencer designed for controlling pulsed or gated events, for rhythm and percussion.

• CGS08 V8 Engine Simulator
  
  A V8 engine sound simulator for revving up your music. A sound-effect module.

• CGS09 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.

• CGS10 Pedal board/Mini Keyboard
  
  A simple circuit that can be used to make a small monophonic 1 volt per octave keyboard, or pedalboard.

• CGS11 D/A Converter
  
  This board was really developed for my own use, to allow my 486 based sequencer to connect to various VCOs etc. It has twelve bit resolution.

• CGS12 Display Adapter
  This board was developed to go with the Wavetable project, allowing easy displaying of the bank and wave numbers.

• CGS13 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.

• CGS14 +/- 15 Volt Power Supply
  
  A simple PSU for use with modules that don't require a more expensive alternative. This is suitable for the gate sequencer, burst generator, V-8 simulator and a number of other CGS projects.

• CGS18 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.

• CGS19 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.

• CGS20 Digitally Controlled Oscillator
  
  This board was really developed for my own use, to allow my 486 based sequencer to drive wavetables etc. It has sixteen bit resolution.

• CGS21 Super Psycho Modulation source.
  
  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.

• CGS22 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.

• CGS23 C.V. Mega Mixer
  
  This module is an enhanced version of the D.C. mixer designed for both audio and CV mixing. It has both non-inverting (adding) and inverting (subtracting) inputs, as well as a master level control. It also features two inverting outputs, one that is offset by the master level control, and the other which has independent offset and center inputs.

• CGS24 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.

• CGS25 Keyboard Scanner sub-module
  
  This board was really developed for my own use, to allow my 486 based sequencer to connect to various keyboards.

• CGS26 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.

• CGS27 Tube VCA and wave folder
  
  This circuit board was designed to allow for easier assembly of 7 pin tube based synthesizer circuits. Going on the number of requests I have had for a tube module that runs on +/- 15 volts, the first project I present using this board is exactly that. It is a simple VCA that doubles as a wave folder/distortion unit. There are no dangers in connection this to solid state modules due to the voltages in use, and the fact that this is really a voltage controlled attenuator, and not an amplifier. There is about 50% signal level loss.

• CGS28 Sequential Switch
  
  A basic switching/sequencing module with many uses.

• CGS29 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.

• CGS30 Bandpass Filter
  
  A utility bandpass filter for creating artifical instrument resonant cavities etc.

• CGS31 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.

• CGS32 Infinite Melody
  
  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.

• CGS33EUR Matrix Mixer
  
  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.

• CGS33 Matrix Mixer
  Discontinued.
  The matrix mixer is a five input, five 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.

• CGS34 Analog Shift Register
  
  Here it is at last - the much requested ASR.
  It is three stages in length, duplicating the functionality of the Serge ASR, but doing it in a very different way. It is great for producing "arabesque-like" sequences, trills etc., when used with VCOs. Of course it's use is not limited to VCOs only.

• CGS35 Steiner Voltage Controlled HP, LP & BP 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.

• CGS35EURO Steiner Voltage Controlled HP, LP & BP Filter
  
  Like the above, this module is a "tribute" module, based on the awesome Steiner-Parker Synthacon VCF. Some circuit improvements such as input level controls and expanded response have been made, as well as a new set of PCBs designed for use in Euro and Frac rack formats.

• CGS36 Pulse Divider and Boolean Logic
  
  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.

• CGS37 C.V. 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.

• CGS38 Saw Pitch Shifter/Wave Multiplier
  
  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.

• CGS39 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.

• CGS40 Modulo Magic
  
  A CV and signal processor based on the mathematical modulo principle. Makes a great wave multipler too!

• CGS41 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.

• CGS42 Gate Sequencer CV Adapter
  
  The CV Adapter is an addition to the Gate Sequencer converting it to a traditional eight-step control voltage sequencer.

• CGS43 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.

• CGS44 Delay Development Board
  
  The Delay Development Board has been designed to allow people to experiment with the Princeton Technologies PT2395 Enhanced Digital Echo IC.

• CGS45 Dome Filter
  
  The dome filter is a 90° phase difference network, as used in frequency shifters. It is not a project in itself, and will be of no use to most people. I designed this board simply because I needed some dome filters for my own experimentation. The boards I am selling are simply left over from this run.

• CGS46 Stomp Box Adapter
  
  The Stomp Box Adapter has been designed to allow some of the regular CGS modules to be used as guitar effects. It has an integral power supply and provides two channels of amplification to bring guitar signal levels up to those used by synthesizers, and two attenuators to drop them again, post effect. It also provides the essential bypass circuit.

• CGS47 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.

• CGS48 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.

• cgs51 Weighted Random Switch
  
  Weighted Random Switch

• cgs52 Simple Wave Folder
  
  The Simple Wave Folder is an ideal beginners project for two reasons - it is simple to build, and its effect is powerful - far beyond what could be suspected from such a simple circuit. The effect it produces is not like unlike that of the Serge middle wave multiplier - harmonically rich waveforms that can be swept for filter-like effects.

• cgs54 XOR XNOR 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.

• cgs55 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.

• cgs56 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.

• cgs57 Bi-N-Tic Voltage controlled Filter/oscillator
  
  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?

• cgs58 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.

• cgs59 Programmer/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.

• CGS60 Stomp Box Adapter
  
  This is a smaller version of the CGS46 Stomp Box Adapter and is basically for use in the reverse situation - namely to allow use of stomp-boxes (effects pedals) as part of a synthesizer setup. While the original will do the kob, this one dispenses with the power supply and bypass switching, and handles a single channel.

• cgs61 Gate Delay
  
  8 channel gate delay (in development)

• CGS62 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.

• CGS63 Power Supply Delay
  
  Does your commercial PSU fail to start propperly? Does one power rail remain off? If so, this module will solve your problems.

• CGS64 VCA
  
  Voltage Controlled Amplifier, suitable for both audio and control voltage modulation.

• CGS65 Tube VCA / timbral Gate
  
  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.

• CGS66 +/- 15 Volt Power Supply
  
  A PSU suitable for use with both digital or analog modules. It can actually be varied to cover a fair range of voltages. It is suitable for use with Eurorack Doepfer standard modules or Modcan and MOTM standard modules.

• CGS69 Dev-mod Gate/Trigger block
  
  A "universal" gate and/or trigger processor for use in developing custom modules, or as a stand alone gate to trigger converter.

• CGS70 Dev-mod Mixer/Inverter block
  
  A "universal" DC mixer and/or analog inverter for use in developing custom modules, or as a stand alone DC mixer.

• CGS71 Dev-mod generic prototyping block
  
  A small board for building your own designs.

• CGS72 Joining Dev-mod blocks together.
  
  Methods, and a small board for joining Dev-mod PCBs together.

• CGS73 Euro power distribution board.
  
  Doepfer compatible power distribution bus board.

Other original designs

• Gated Comparator
• Gate Sequencer
• Organ Interface
• V-8 and Diesel simulators
• Modifying the arc-welder for synth apps.

Tube modules

Other modules I have built are tube based, including one that uses thirteen tubes. This contains two 1 volt/oct VCOs, a pair of "modulators", a beam tube modulator and a VCF designed by René Schmitz.

• Tube bandpass VCF
• Metasonix Hellfire Modulator
• Power supply for tube modules
• Beam Modulator

Individual construction of modules based on the original designs of Ken Stone is encouraged. PCBs are available for some of these designs directly from the designer. Commercial production of these designs is prohibited without written permission from the designer, Ken Stone. Note that no guarantees are given for any of these designs.

Where a design is copyright by a third party, details of that design are not given, rather a way of researching the information or contacting the designer is given instead.

Article, art & design copyright 1999 by Ken Stone

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