Difference between pages "CGS Serge voltage controlled wave multiplier" and "CGS burst generator"

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[[File:cgs_photo_cgs113_vcm.jpg|thumb|center|800px|]]
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'''CGS06''' the '''CGS burst generator''' module is a rhythm and timing accessory. It generates a burst of gate or trigger pulses at various speeds as set from a front panel control.
'''CGS113''' the '''CGS Serge voltage controlled wave multiplier''' module is based on the Serge Wave Multipliers.
 
   
  +
At higher speeds it can be used for washboard, maracas or similar rapid-burst percussive effects when connected to the appropriate sound generating device such as a ringing oscillator.
== Description ==
 
[[File:cgs_panel_cgs113_vcm.gif|thumb|right|231px]]
 
To quote the 1982 Serge catalog:
 
   
  +
At lower speeds it can be used to step a sequencer a certain number of steps or retrigger an envelope shaper. The output pulses are quite narrow when the specified component values are used, and would best be described as trigger pulses in synths that distinguish gates from triggers. Increasing some component values will give longer gate like pulses.
:For generating and modifying sound, the typical synthesizer patch is VCO-VCF-VCA, linked in series, with suitable control from keyboard, sequencer, or computer. The VCO generates the raw sound, the VCF dynamically varies the timbre (sound quality). and the VCA controls the amplitude and produces the envelope on the sound event. The Serge Modular WAVE MULTIPLIERS (VCM) provide a new link in this chain, representing an advance in synthesizer technology. In this typical patch, the Wave Multiplier could be placed just before the VCF. Like the VCF. the Wave Multiplier affects the timbre. Unlike the VCF, whose action is a subtractive process of filtering frequencies from the input waveform, the Wave Multipliers are able to dynamically process the input waveform to produce new harmonically-related overtones. This function should not be confused with Ring Modulation, since it is a non-linear process using a single audio input. Although it is possible to describe the effect of a VCF by saying the sound gets "bass-heavy", makes a "wah-wah" effect, or sounds "thin" to describe the sound of a Wave Multiplier is much more difficult. The input sound comes out richer in harmonics, somewhat similar to pulse-width modulation and to linear frequency modulation, but with a new characteristic timbre. The nearest we can come to describing the unique sound qualities (there are three different sections) is to say that they alter the timbre in exciting new ways, producing interesting alternative forms of signal processing which are unique in the Serge Modular Music System. Since there are three entirely separate and different types of Wave Multipliers in this module, an enormously varied palette of new effects can be synthesized.
 
   
  +
== How to use this module ==
:The uppermost section is the simplest of the three multiplier sections. but it has two switchable effects. With the switch set at the "HI" position, the module functions to "square-up" an incoming signal. This is not the same as a simple comparator squaring function, though, since there is a rounded flattening of the signal peaks: an effect somewhat similar to overdriving a tube amplifier (except that in this version the process is voltage controllable!). With the switch in the "LO" position, the module is a linear gain controlled VCA. This is useful for various functions such as amplitude modulation and for gating signals into the other sections.
 
  +
Here's a few ideas to get you started. It can be used alone or cascaded with other burst generators. When cascaded, it could form the basis of a weird rhythm/timing generator. It could be used to step your sequencer through so many notes each down-beat. Fed to the modulation input of a VCO either directly or via an envelope shaper, it will cause a trill at the beginning of each note. It can use either its internal synchronized clock, or an external clock. It can be configured to be retriggerable or not, in which case the event in progress is concluded before it will respond to another. Experiment with it.
 
:The middle Wave Multiplier provides a sweep of the odd harmonics (1, 3, 5, 7, 9, 11 and 13th) when a sine wave is applied to its input and the knob is turned up or a control voltage is swept from low to high. This effect is similar to overblowing a wind pipe closed at one end, and thus the module can be used to produce the sounds of various wind instruments. A second input is included to allow two signals to be mixed before processing, a technique that we have found to be very usable. This module can be used to explore timbral areas beyond the range of ring modulation because there are more varied harmonics than the sum and difference tones.
 
 
:The bottom Wave Multiplier performs non-linear waveshaping known as full-wave rectification, but with sophisticated level-compensating conditioning as well. Actually the circuit uses three full-wave rectifier sections linked in a very refined controllable format. Each section can double the frequency of a sine or triangle wave applied to its input. Thus sweeping the VC input over its range will produce a smooth timbral transition using the even harmonics (second, fourth, and eighth). Many other partials are present in this basic sound, however, and the sonorities are very rich and varied. A notable feature of this multiplier is that the full-wave rectification is not accompanied by a reduction in the output amplitude. There is no alteration of the essential level of the sound. There are two inputs to provide mixing before processing, and two outputs. One output is a "squared up" version of the other. This output resembles voltage controlled pulse width modulation (only much more interesting). The Wave Multipliers are among the most powerful timbral modifiers available on any analog music synthesizer. The rich varieties of inter-patch possibilities are nearly inexhaustible, and these possibilities combined with the flexibility of other Serge modules will provide unique synthesis tools for the person who is eager to experiment with entirely new classes of sounds. The Wave Multipliers provide what has too often been lacking in electric musics. a means of generating sounds as complex and dynamically variable as those found in acoustic sound sources. Yet these are also precision modules which respond accurately to control voltages, so they may be used to give repeatable results in the most exacting analog or digital applications.
 
 
It will work on either +/- 12 volts or +/-15 volts without modification, though in the case of the latter, all input voltage sensitivities, and output voltages are proportionally increased.
 
   
 
== A little on how it works ==
 
== A little on how it works ==
[[File:cgs_schem_cgs113_vcm1.gif|thumb|center|784px|The upper multiplier functions as a basic distortion unit, or a VCA, depending on the mode selected.]]
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[[File:cgs_schem_burst_generator.gif|thumb|center|600px|The schematic of the Burst Generator.]]
  +
[[File:cgs_panel_burst_generator.jpg|thumb|right|102px|]]
  +
The circuit consists of several distinct blocks. The first are the input shapers, made from IC1A and IC1B and their associated components. These take whatever signal is fed into the module and convert them to signals appropriate for driving the rest of the circuitry. With the values given, the sensitivity is set at around 1.4V, allowing triggering from signals with a +/- 10 volt swing, or with a 0V to +10 volt swing, both of which are common in modulars. The output waveforms of some modules will never fall below the 1.4V level, preventing triggering. This can be solved by increasing the value of the 10k resistor between pin 3 of IC1 and ground to 22k, or higher if needed.
   
  +
IC1A is part of the circuit used to trigger the burst event. Coupled with IC1F and its associated components, it forms a "gate to trigger converter", generating a narrow positive going pulse when the "Trigger" input goes above the 1.4 volt threshold. This pulse is buffered and sent to an output jack for external use if needed. It also sends a pulse to the reset pin the 4017 via a simple AND gate. (More on this later).
[[File:cgs_schem_cgs113_vcm2.gif|thumb|center|808px|The middle multiplier provides a sweep of the odd harmonics (1, 3, 5, 7, 9, 11 and 13th). This gives the most amazing filter like sweeps, by adding harmonic content to the input wave.]]
 
   
  +
IC1B is used to process the "External Clock" input. The frequency of the clock signal determines the speed of the output pulses. It can be either an external clock derived from an LFO, sequencer or similar, or from the internal clock circuit, which is normalized to the input jack.
[[File:cgs_schem_cgs113_vcm3.gif|thumb|center|810px|The bottom Wave Multiplier performs controlled full-wave rectification to add even harmonics.]]
 
   
  +
Unlike any external clock signal, the internal clock is synchronized so that it generates a series of even length pulses when the burst generator is triggered. It has two ranges, selected by switching in or out a 330nF capacitor. The 2 meg pot specified for speed is not critical, and be anything from 1M to 5M, though obviously this will affect the range.
== Construction ==
 
[[File:cgs_pcb_cgs113_vcm.gif|thumb|center|800px|The component overlay for the VER1.0 PCB. Omit the parts filled in red. Use component value given in red. Capacitor CK is 47pF. Click through for an enlarged, printable version. Print at 300dpi.]]
 
[[File:cgs_pcb_cgs113v11_vcm.gif|thumb|center|800px|The component overlay for the VER1.1 PCB. Capacitors marked *1 are 47pF. Install as needed - see text. Click through for an enlarged, printable version. Print at 300dpi.]]
 
Before you start assembly, check the board for etching faults. Look for any shorts between tracks, or open circuits due to over etching. Take this opportunity to sand the edges of the board if needed, removing any splinters or rough edges.
 
   
  +
The output of IC1B is fed to the clock input of the 4017 decade counter, and also to an AND gate consisting of a 100k resistor and 1N4148 diode. The output of this AND gate goes to a pulse generator made from IC2E, IC2D and associated components. This pulse generator functions very similarly to the gate to trigger converter mentioned above, converting each cycle of the clock signal to a narrow pulse. This is buffered and sent to an external jack, and is the primary output of this module, namely a burst of pulses.
When you are happy with the printed circuit board, construction can proceed as normal, starting with the resistors first, followed by the IC sockets if used, then moving onto the taller components.
 
   
  +
The 4017 decade counter forms the heart of the module. When reset, it counts up to the number selected by the switch connected to its outputs at the speed determined by the clock frequency. If we consider the rotary switch to be set to position "2" as shown in the schematic, the second clock pulse sent to the 4017 after it has been reset will present a logic HIGH to its Clock Inhibit pin (13) via the diode OR gate. This will stop the counter at that point, and any further clock pulses will be ignored. This inhibit signal is also inverted by IC2B and sent to the AND gate preventing the clock signal from reaching the second pulse generator. The inhibit signal also sends the event "End Out" output high.
Take particular care with the orientation of the polarized components, such as electrolytics, diodes, transistors and ICs.
 
   
  +
The inhibit signal is reinverted and fed to another diode/resistor AND gate at the Reset input of the 4017, and another output buffer, this one for event "Duration Out". While the burst event is occurring the Clock Inhibit pin of the 4017 is held low via the 100k resistor. IC2B inverts this, presenting a HIGH to the event "Duration Out" buffer, the clock control AND gate and the input of IC2A. This will cause the output of IC2A to be LOW. If the Retrigger switch is closed, this LOW will hold the Reset pin of the 4017 LOW via the diode, preventing the event from being retriggered by any more pulses appearing on the "Trigger" input, thus preventing retriggering of the burst.
When inserting the ICs in their sockets, take care not to accidentally bend any of the pins under the chip. Also, make sure the notch on the chip is aligned with the notch marked on the PCB overlay.
 
   
  +
How do the resistor/diode AND gates work? First, consider the outputs of both IC1B and IC2B to be HIGH. The input of IC2E, will be pulled HIGH via the 100k resistor. As the cathode of the diode is also being held HIGH, the diode has no effect on the input of IC2E. When the output of IC1B falls LOW, the diode will be forward biased, pulling the input of IC2E LOW with it. Alternately, if the output of IC2B is LOW when the output of IC1B is HIGH, the input of IC2E is pulled low via the 100k resistor as the diode will be reversed biased, blocking the HIGH from IC1B. When the outputs of both IC1B and IC2B are both low, it should be fairly obvious the input of IC2E will also be low. Thus, if either or both inputs are LOW, the output will also be LOW.
Note that there are several capacitors on the PCB that should be omitted. They are shown in red on the overlay above. Some are marked 30pF on the PCB itself.
 
   
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=== Summary of inputs, outputs and controls ===
Although the PCB calls for the use of 4558 dual op-amps, the type actually used varied somewhat from build to build. I would recommend using TL072, which appear to be the most stable in the circuit. If you wish to use other varieties, check that none of the op-amps have gone into self oscillation. On my prototype, I needed to add 47pf across pins 6 and 7 of the top 4558. Another test builder found he required caps on each of the op-amps in the section, as shown on the schematic (marked *1). These can be soldered directly to the rear of the PCB at the IC pins. Chips on the schematic are identified via color code, the colors corresponding to the colors of the resistor color code. The chips on the board are numbered from top to bottom, left to right, with the unused 16 pin location being IC0.
 
  +
* '''External Clock''' - Normalized to the internal clock, but can be overridden by plugging in an external signal. Waveshape is not critical, as long as the waveform passes the trigger point.
  +
* '''Trigger''' - Input for the external signal needed to start the event. Waveshape is not critical, as long as the waveform passes the trigger point.
  +
* '''Pulses'''. Output for the burst event.
  +
* '''Trigger Out'''. Output for the trigger signal derived from the Trigger input.
  +
* '''Event Duration'''. Output. Goes high for the duration of the event. i.e. for the period the '''Pulses''' output is active
  +
* '''End Out''' Output. Goes high when the burst event is over. This can be used to trigger another module if you wish to cascade them.
  +
* '''Clock Speed'''. The rate at which the internal clock runs.
  +
* '''Range'''. High and low range for the internal clock.
  +
* '''Pulses'''. Select between 1 and 9 pulses per event.
  +
* '''Retrigger'''. When the switch is closed, the unit cannot be retriggered during an event.
   
  +
=== Notes ===
IC0 is to allow an LM13700 or similar to be used in place of the two LM/CA3080. Wire the corresponding pins of the first LM3080 location to the pads marked with their numbers on left side of IC0 (5, 3, 2 and 6). Do the same for the second LM3080 to the correspondingly marked pads on the right side of the chip (5, 3, 2, 6 and 4).
 
  +
* The length of the reset/trigger out pulse can be increased by increasing the value of the 100k resistor marked "#" on the schematic and PCB, or by increasing the value of the 10n capacitor associated with it. Increasing it too much will mess up the timing of the burst, as it will hold the reset pin of the 4017 high for the full length of this pulse.
  +
* The length of the clock pulse presented at the "Pulses out" jack can be increased by increasing the value of the 100k resistor marked "*" on the schematic and PCB, or by increasing the value of the 10n capacitor associated with it. Increasing it too much will limit the maximum burst rate, as the pulses will all run together. If a DPDT switch is used for the "Range" function, a second capacitor could be added across the 10n capacitor when the lower speed range is selected, giving longer output pulses when most likely to be needed. The adventurous could increase the capacitor to 100n, drop the resistor to 10k, and put a 100k pot in series with it. This pot could be mounted on the panel, giving full control of the pulse length.
  +
* The diodes and associated resistors around the internal clock oscillator disable the oscillator and prime it for the next burst when an event is over. In theory it halts the oscillator just after the beginning of its cycle. This is so when reset, a full cycle period will pass before the 4017 receives it's first clock pulse. When external clocks are used, there is no way to do this synchronizing.
  +
* 40106/74C14 chips by different manufacturers will have different speeds. This will affect the timing of various parts of this module, though should not cause any problems, perhaps with the exception of the internal clock synchronization.
  +
* The LED and its associated resistor are unassigned. They are there for people who cannot live without a pilot light, or something that flashes. If you don't want them, don't install them. Mine is connected with the cathode to 0V and the anode to the emitter of the transistor driving the "Duration Out" output.
  +
* If you have separate digital and analog power supplies for your synth, connect this one to the digital supply. CGS14 [[CGS ±15V power supply|±15V Power Supply]].
  +
* The module will work on +/-12 to +/-15 volts.
  +
* I have used BC547 transistors. These are generic NPN silicon signal transistors. Any common signal NPN should work. Emitter, Base and Collector (ebc) are marked on one transistor on the PCB to help you substitute other devices.
   
  +
== Construction ==
You will need to add some 30pF capacitors across pins 10 and 11 of IC 7 and pins 3 and 4 of IC8 if the third multiplier shows any instability. Again, use an oscilloscope to check. If you do not have access to a scope, with no input into the multiplier, plug the output into a VCO. The VCO frequency will usually jump up of there is a stability issue.
 
  +
{| align="center"
  +
| [[File:cgs_pcb_burst_generator.gif|thumb|center|201px|The overlay of the Burst Generator.]]||[[File:cgs_photo_burst_generator1.jpg|thumb|right|208px|]]
  +
|}
  +
Before you start assembly, check the board for etching faults. Look for any shorts between tracks, or open circuits due to over etching. Take this opportunity to sand the edges of the board if needed, removing any splinters or rough edges.
   
  +
When you are happy with the printed circuit board, construction can proceed as normal, starting with the diodes and resistors first, followed by the IC sockets if used, then moving onto the taller components.
[[File:cgs_photo_cgs113_vcm1.jpg|thumb|center|800px|Additional capacitors soldered to the rear of the PCB as required.]]
 
   
  +
Take particular care with the orientation of the polarized components, the diodes, LED, electrolytic capacitors and the transistors and ICs. You may want to leave soldering in the LED until you work out what height they will need to be to pass through hole in the panel.
{| class="wikitable"
 
!Pad!!Identification
 
|-
 
| CK||47pF
 
|-
 
| A||In 1, middle section
 
|-
 
| B||In 2, middle section
 
|-
 
| C||VC, middle section
 
|-
 
| D||Pot wiper, middle section
 
|-
 
| E||In 1, bottom section
 
|-
 
| F||In 2, bottom section
 
|-
 
| G||In, top section
 
|-
 
| H||Pot wiper, top section
 
|-
 
| J||Switch, top section
 
|-
 
| K||Switch, top section
 
|-
 
| KO||Output, top section
 
|-
 
| L||Switch, top section
 
|-
 
| M||Output 1, bottom section
 
|-
 
| N||Output 2, bottom section
 
|-
 
| R||Pot wiper, bottom section
 
|-
 
| S||Control voltage, bottom section
 
|-
 
| +VE||+ve for CW end of all pots
 
|-
 
| U||0V/GND for CCW end of all pots
 
|-
 
| X||+VE in
 
|-
 
| W||0V in
 
|-
 
| Z||VE in
 
|-
 
| 0V||0V/GND connection for 3.5 or 6.5mm jacks and CCW end of level pot.
 
|}
 
   
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When inserting the ICs in their sockets, take care not to accidentally bend any of the pins under the chip. Also, make sure the notch on the chip is aligned with the notch marked on the PCB overlay. Please note that the CMOS chips are static sensitive devices, so make sure you handle them correctly.
[[File:cgs_wire_cgs113_vcm.jpg|thumb|center|610px|Example wiring for the Wave Multipliers. Note the 330k resistor soldered directly to the switch.]]
 
   
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The rotary switch chosen solders directly onto the PCB. It is deliberately a tight fit. The pins may need tweaking so they go through the holes. Under the nut and washer there is a special washer that allows you to set the maximum range of the switch. Turn the switch fully anti-clockwise, then insert the washer so that its tab goes between holes 9 and 10. The one in the photo does not have the washer installed. Due to the configuration of the board, the direction in which you mount the board will affect the home position of the switch, and thus the flat of the shaft may be pointing in an inappropriate direction for your panel label. File yourself a new flat, if you feel it necessary. The knob on the prototype was such a tight fit no flat was needed.
== Setup ==
 
Two trim pots are supplied to adjust CV rejection on the top two wave multipliers. If you have access to an oscilloscope, use it. If not, use an audio signal, and monitor the output with an amplifier.
 
   
  +
If you wish to use a MOTM style power connector, you will either need to use a 90° connector or to mount it on flying leads. There is insufficient space between the PCB and the panel for a regular connector to fit.
Feed a signal into the CV input of the upper wave multiplier. Monitor its output. Adjust TR1 for minimum output.
 
   
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When mounting this boards on the front panel, you will find that the height of the switch will determine the required gap. You may prefer to mount the PCB on a sub panel, and just pass the long switch shaft through a smaller hole on the front panel. That will also afford your more clearance for other components. Alternatively, you could use longer stand-offs to give more space.
Feed a signal into the CV input of the middle wave multiplier. Monitor its output. Adjust TR2 for minimum output.
 
   
 
== Parts list ==
 
== Parts list ==
Line 111: Line 76:
 
! colspan="2" align=center|Capacitors
 
! colspan="2" align=center|Capacitors
 
|-
 
|-
| 30pF||align=right|4
+
| 10n||align=right|2
 
|-
 
|-
| 47pF||align=right|2 (8)
+
| 100n||align=right|3
 
|-
 
|-
| 150pF||align=right|1
+
| 330n||align=right|1
 
|-
 
|-
| 47n||align=right|4
+
| 10uF 25V||align=right|1
 
|-
 
|-
  +
! colspan="2" align=center|Resistors
| 100n (0.1 ceramic monolithic or similar)||align=right|6
 
 
|-
 
|-
| 220n||align=right|2
+
| 1k||align=right|6
 
|-
 
|-
| 1uF BP 25V||align=right|3
+
| 10k||align=right|5
 
|-
 
|-
| 10uF 25V||align=right|2
+
| 15k||align=right|2
 
|-
 
|-
| 47uF 25V||align=right|1
+
| 22k||align=right|2
|-
 
! colspan="2" align=center|Resistors (1% metal film)
 
|-
 
| 330R (330 Ohms)||align=right|2
 
|-
 
| 1k5||align=right|4
 
|-
 
| 3k3||align=right|2
 
|-
 
| 10k||align=right|2
 
|-
 
| 15k||align=right|1
 
|-
 
| 22k||align=right|1
 
|-
 
| 33k||align=right|6
 
 
|-
 
|-
 
| 47k||align=right|1
 
| 47k||align=right|1
 
|-
 
|-
| 82k||align=right|1
+
| 100k||align=right|8
 
|-
 
|-
| 100k||align=right|20
+
! colspan="2" align=center|Semi's
 
|-
 
|-
| 150k||align=right|1
+
| 1N4148||align=right|8
 
|-
 
|-
| 220k||align=right|2
+
| 4017||align=right|1
 
|-
 
|-
| 330k||align=right|4
+
| 40106 or 74C14||align=right|1
 
|-
 
|-
| 470k||align=right|1
+
| BC547||align=right|4
 
|-
 
|-
| 820k||align=right|3
+
| LED (optional)||align=right|1
 
|-
 
|-
| 1M||align=right|5
+
| LM358||align=right|1
 
|-
 
|-
| 1M5||align=right|1
+
! colspan="2" align=center|Misc
 
|-
 
|-
  +
| Wire
| 2M2||align=right|4
 
 
|-
 
|-
| 3M3||align=right|2
+
| 2M lin pot||align=right|1
 
|-
 
|-
| 6M8||align=right|1
+
| SPDT switch||align=right|2
 
|-
 
|-
| 10M||align=right|6
+
| Alpha 12 position switch||align=right|1
 
|-
 
|-
| 100k trim||align=right|2
+
| Ferrite bead (or 10R resistor)||align=right|1
 
|-
 
|-
| 50k or 100k lin pot||align=right|3
+
| Knobs||align=right|2
 
|-
 
|-
  +
| Jacks||align=right|6
! colspan="2" align=center|Semi's
 
|-
 
| 4V3 or 4V6 400 or 500mW Zener (DZ)||align=right|1
 
|-
 
| 1N4148||align=right|22
 
|-
 
| 2N4250 (BC557 or sim)||align=right|2
 
|-
 
| LM3080 or CA3080||align=right|2
 
|-
 
| LM3900||align=right|2
 
|-
 
| TL072 (4558)||align=right|4
 
|-
 
! colspan="2" align=center|Misc
 
|-
 
| Jacks||align=right|12 (7 black, 5 blue)
 
|-
 
| DPDT switch||align=right|1
 
|-
 
| Ferrite bead (or 10R resistor)||align=right|2
 
 
|-
 
|-
 
| 0.156 4 pin connector||align=right|1
 
| 0.156 4 pin connector||align=right|1
 
|-
 
|-
| CGS113 VER1.0 PCB||align=right|1
+
| CGS06 PCB||align=right|1
 
|}
 
|}
   
=== Notes ===
+
== CC-BY-NC ==
  +
Readers are permitted to construct these circuits for their own personal use only. Ken Stone retains all rights to his work.
* 330R refers to 330 ohms. 100n = 0.1 uF.
 
* PCB is 6" x 2" with 3mm mounting holes 0.15" in from the edges.
 
   
 
== See also ==
 
== See also ==
Line 213: Line 141:
   
 
== References ==
 
== References ==
* ''[https://web.archive.org/web/20180209234737fw_/http://www.cgs.synth.net:80/modules/cgs113_vcm.html Serge Wave Multipliers for music synthesizers.]'' (archived) by Ken Stone, 2012, with permission of the author
+
* [https://web.archive.org/web/20170525063958f/http://www.cgs.synth.net:80/modules/burst_generator.html Burst Generator for music synthesizers.] (archived) by Ken Stone, 2001, with permission of the author
   
 
== External links ==
 
== External links ==
* [http://www.serge.synth.net/documents/kit/vcwm.html VC Wave Multipliers], the original Serge kit instructions.
 
 
* [http://groups.yahoo.com/group/cgs_synth CGS Synth discussion group], for discussion of locating parts, modifications and corrections etc.
 
* [http://groups.yahoo.com/group/cgs_synth CGS Synth discussion group], for discussion of locating parts, modifications and corrections etc.
* [http://bompiler.com/pcb/cgs113 CGS113 BOM] at BOMpiler
+
* [http://bompiler.com/pcb/cgs06 CGS06 BOM] at BOMpiler
 
=== Suppliers ===
 
=== Suppliers ===
* [http://www.elby-designs.com/webtek/cgs/serge/cgs113/cgs113_vcm.html CGS113 Wave Multipliers], revision 1.1, Elby Designs
+
* [http://www.elby-designs.com/webtek/cgs/cgs06/cgs06_burst_generator.html CGS06 Burst Generator], Elby Designs
   
 
[[Category:CGS modular]]
 
[[Category:CGS modular]]

Revision as of 10:37, 7 June 2019

Cgs photo burst generator2.jpg

CGS06 the CGS burst generator module is a rhythm and timing accessory. It generates a burst of gate or trigger pulses at various speeds as set from a front panel control.

At higher speeds it can be used for washboard, maracas or similar rapid-burst percussive effects when connected to the appropriate sound generating device such as a ringing oscillator.

At lower speeds it can be used to step a sequencer a certain number of steps or retrigger an envelope shaper. The output pulses are quite narrow when the specified component values are used, and would best be described as trigger pulses in synths that distinguish gates from triggers. Increasing some component values will give longer gate like pulses.

How to use this module

Here's a few ideas to get you started. It can be used alone or cascaded with other burst generators. When cascaded, it could form the basis of a weird rhythm/timing generator. It could be used to step your sequencer through so many notes each down-beat. Fed to the modulation input of a VCO either directly or via an envelope shaper, it will cause a trill at the beginning of each note. It can use either its internal synchronized clock, or an external clock. It can be configured to be retriggerable or not, in which case the event in progress is concluded before it will respond to another. Experiment with it.

A little on how it works

The schematic of the Burst Generator.
Cgs panel burst generator.jpg

The circuit consists of several distinct blocks. The first are the input shapers, made from IC1A and IC1B and their associated components. These take whatever signal is fed into the module and convert them to signals appropriate for driving the rest of the circuitry. With the values given, the sensitivity is set at around 1.4V, allowing triggering from signals with a +/- 10 volt swing, or with a 0V to +10 volt swing, both of which are common in modulars. The output waveforms of some modules will never fall below the 1.4V level, preventing triggering. This can be solved by increasing the value of the 10k resistor between pin 3 of IC1 and ground to 22k, or higher if needed.

IC1A is part of the circuit used to trigger the burst event. Coupled with IC1F and its associated components, it forms a "gate to trigger converter", generating a narrow positive going pulse when the "Trigger" input goes above the 1.4 volt threshold. This pulse is buffered and sent to an output jack for external use if needed. It also sends a pulse to the reset pin the 4017 via a simple AND gate. (More on this later).

IC1B is used to process the "External Clock" input. The frequency of the clock signal determines the speed of the output pulses. It can be either an external clock derived from an LFO, sequencer or similar, or from the internal clock circuit, which is normalized to the input jack.

Unlike any external clock signal, the internal clock is synchronized so that it generates a series of even length pulses when the burst generator is triggered. It has two ranges, selected by switching in or out a 330nF capacitor. The 2 meg pot specified for speed is not critical, and be anything from 1M to 5M, though obviously this will affect the range.

The output of IC1B is fed to the clock input of the 4017 decade counter, and also to an AND gate consisting of a 100k resistor and 1N4148 diode. The output of this AND gate goes to a pulse generator made from IC2E, IC2D and associated components. This pulse generator functions very similarly to the gate to trigger converter mentioned above, converting each cycle of the clock signal to a narrow pulse. This is buffered and sent to an external jack, and is the primary output of this module, namely a burst of pulses.

The 4017 decade counter forms the heart of the module. When reset, it counts up to the number selected by the switch connected to its outputs at the speed determined by the clock frequency. If we consider the rotary switch to be set to position "2" as shown in the schematic, the second clock pulse sent to the 4017 after it has been reset will present a logic HIGH to its Clock Inhibit pin (13) via the diode OR gate. This will stop the counter at that point, and any further clock pulses will be ignored. This inhibit signal is also inverted by IC2B and sent to the AND gate preventing the clock signal from reaching the second pulse generator. The inhibit signal also sends the event "End Out" output high.

The inhibit signal is reinverted and fed to another diode/resistor AND gate at the Reset input of the 4017, and another output buffer, this one for event "Duration Out". While the burst event is occurring the Clock Inhibit pin of the 4017 is held low via the 100k resistor. IC2B inverts this, presenting a HIGH to the event "Duration Out" buffer, the clock control AND gate and the input of IC2A. This will cause the output of IC2A to be LOW. If the Retrigger switch is closed, this LOW will hold the Reset pin of the 4017 LOW via the diode, preventing the event from being retriggered by any more pulses appearing on the "Trigger" input, thus preventing retriggering of the burst.

How do the resistor/diode AND gates work? First, consider the outputs of both IC1B and IC2B to be HIGH. The input of IC2E, will be pulled HIGH via the 100k resistor. As the cathode of the diode is also being held HIGH, the diode has no effect on the input of IC2E. When the output of IC1B falls LOW, the diode will be forward biased, pulling the input of IC2E LOW with it. Alternately, if the output of IC2B is LOW when the output of IC1B is HIGH, the input of IC2E is pulled low via the 100k resistor as the diode will be reversed biased, blocking the HIGH from IC1B. When the outputs of both IC1B and IC2B are both low, it should be fairly obvious the input of IC2E will also be low. Thus, if either or both inputs are LOW, the output will also be LOW.

Summary of inputs, outputs and controls

  • External Clock - Normalized to the internal clock, but can be overridden by plugging in an external signal. Waveshape is not critical, as long as the waveform passes the trigger point.
  • Trigger - Input for the external signal needed to start the event. Waveshape is not critical, as long as the waveform passes the trigger point.
  • Pulses. Output for the burst event.
  • Trigger Out. Output for the trigger signal derived from the Trigger input.
  • Event Duration. Output. Goes high for the duration of the event. i.e. for the period the Pulses output is active
  • End Out Output. Goes high when the burst event is over. This can be used to trigger another module if you wish to cascade them.
  • Clock Speed. The rate at which the internal clock runs.
  • Range. High and low range for the internal clock.
  • Pulses. Select between 1 and 9 pulses per event.
  • Retrigger. When the switch is closed, the unit cannot be retriggered during an event.

Notes

  • The length of the reset/trigger out pulse can be increased by increasing the value of the 100k resistor marked "#" on the schematic and PCB, or by increasing the value of the 10n capacitor associated with it. Increasing it too much will mess up the timing of the burst, as it will hold the reset pin of the 4017 high for the full length of this pulse.
  • The length of the clock pulse presented at the "Pulses out" jack can be increased by increasing the value of the 100k resistor marked "*" on the schematic and PCB, or by increasing the value of the 10n capacitor associated with it. Increasing it too much will limit the maximum burst rate, as the pulses will all run together. If a DPDT switch is used for the "Range" function, a second capacitor could be added across the 10n capacitor when the lower speed range is selected, giving longer output pulses when most likely to be needed. The adventurous could increase the capacitor to 100n, drop the resistor to 10k, and put a 100k pot in series with it. This pot could be mounted on the panel, giving full control of the pulse length.
  • The diodes and associated resistors around the internal clock oscillator disable the oscillator and prime it for the next burst when an event is over. In theory it halts the oscillator just after the beginning of its cycle. This is so when reset, a full cycle period will pass before the 4017 receives it's first clock pulse. When external clocks are used, there is no way to do this synchronizing.
  • 40106/74C14 chips by different manufacturers will have different speeds. This will affect the timing of various parts of this module, though should not cause any problems, perhaps with the exception of the internal clock synchronization.
  • The LED and its associated resistor are unassigned. They are there for people who cannot live without a pilot light, or something that flashes. If you don't want them, don't install them. Mine is connected with the cathode to 0V and the anode to the emitter of the transistor driving the "Duration Out" output.
  • If you have separate digital and analog power supplies for your synth, connect this one to the digital supply. CGS14 ±15V Power Supply.
  • The module will work on +/-12 to +/-15 volts.
  • I have used BC547 transistors. These are generic NPN silicon signal transistors. Any common signal NPN should work. Emitter, Base and Collector (ebc) are marked on one transistor on the PCB to help you substitute other devices.

Construction

The overlay of the Burst Generator.
Cgs photo burst generator1.jpg

Before you start assembly, check the board for etching faults. Look for any shorts between tracks, or open circuits due to over etching. Take this opportunity to sand the edges of the board if needed, removing any splinters or rough edges.

When you are happy with the printed circuit board, construction can proceed as normal, starting with the diodes and resistors first, followed by the IC sockets if used, then moving onto the taller components.

Take particular care with the orientation of the polarized components, the diodes, LED, electrolytic capacitors and the transistors and ICs. You may want to leave soldering in the LED until you work out what height they will need to be to pass through hole in the panel.

When inserting the ICs in their sockets, take care not to accidentally bend any of the pins under the chip. Also, make sure the notch on the chip is aligned with the notch marked on the PCB overlay. Please note that the CMOS chips are static sensitive devices, so make sure you handle them correctly.

The rotary switch chosen solders directly onto the PCB. It is deliberately a tight fit. The pins may need tweaking so they go through the holes. Under the nut and washer there is a special washer that allows you to set the maximum range of the switch. Turn the switch fully anti-clockwise, then insert the washer so that its tab goes between holes 9 and 10. The one in the photo does not have the washer installed. Due to the configuration of the board, the direction in which you mount the board will affect the home position of the switch, and thus the flat of the shaft may be pointing in an inappropriate direction for your panel label. File yourself a new flat, if you feel it necessary. The knob on the prototype was such a tight fit no flat was needed.

If you wish to use a MOTM style power connector, you will either need to use a 90° connector or to mount it on flying leads. There is insufficient space between the PCB and the panel for a regular connector to fit.

When mounting this boards on the front panel, you will find that the height of the switch will determine the required gap. You may prefer to mount the PCB on a sub panel, and just pass the long switch shaft through a smaller hole on the front panel. That will also afford your more clearance for other components. Alternatively, you could use longer stand-offs to give more space.

Parts list

This is a guide only. Parts needed will vary with individual constructor's needs.

Part Quantity
Capacitors
10n 2
100n 3
330n 1
10uF 25V 1
Resistors
1k 6
10k 5
15k 2
22k 2
47k 1
100k 8
Semi's
1N4148 8
4017 1
40106 or 74C14 1
BC547 4
LED (optional) 1
LM358 1
Misc
Wire
2M lin pot 1
SPDT switch 2
Alpha 12 position switch 1
Ferrite bead (or 10R resistor) 1
Knobs 2
Jacks 6
0.156 4 pin connector 1
CGS06 PCB 1

CC-BY-NC

Readers are permitted to construct these circuits for their own personal use only. Ken Stone retains all rights to his work.

See also

References

External links

Suppliers