Difference between pages "CGS voltage controlled divider" and "CGS tube VCA and wave folder"

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'''CGS27''' the '''CGS tube VCA wave folder''' 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 connecting 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.
'''CGS09''' the '''CGS voltage controlled divider''' module is an upgraded version of my older voltage controlled divider. It has additional mixing and a comparator at the clock input, additional range, and will now work on 12V if needed, as the internal regulator has been eliminated.
 
 
This was originally developed a timing accessory for a sequencer I was working on, though when fed from a VCO, interesting frequency trills like those of the old 8-bit computer games can be produced. Feeding the control voltage from a [[CGS psycho LFO|Psycho LFO]] produces some interesting effects.
 
 
There are two outputs, one a narrow "trigger" pulse, the other following the pulse width of the incoming signal. This means that any mark/space ratio sweep being applied to a VCO connected to this module, will also be on the output signal of this module.
 
 
The division can be varied from divide by 1 to approximately divide by 60.
 
   
 
== How to use this module ==
 
== How to use this module ==
  +
Connect a signal such as a VCO output to the signal input of the tube module. Feed the output to an amplifier or other signal processing module. Turn the LEVEL pot to maximum. This sets the gain to maximum. When fed an 8V peak to peak triangle wave, the first half of the travel of the DRIVE pot acts as an input level control. The second half of the travel sets the amount of overdrive/wave folding. A DC offset voltage can be added to the input signal via an external CD mixer to allow shifting of the fold point, animating the output signal.
Connect the input to a signal source such as a VCO, LFO or sequencer master clock. Use the control voltage input to determine the number of incoming pulses per output pulse.
 
   
  +
A control voltage can be used to control the output level, in which case the LEVEL pot controls the amount of effect the control voltage has. This signal needs to be above 0 volts to turn the VCA on, though negative voltages will not hurt it. put.
There are two pulse outputs, marked HO and LO on the PCB. HO (High Frequency out) gives a narrow trigger pulse output. LO (Low Frequency out) gives a pulse output, the width of which varies with the pulse width of the incoming signal. Depending on the individual ICs you use, the propagation delays of the chips will limit the speed at which the LO output can function. I estimate it drops out above 10 kHz, though as mentioned, it does vary with individual 40106 chips.
 
   
 
== A little on how it works ==
 
== A little on how it works ==
[[File:cgs_schem_cgs09_ncom_r2s.gif|thumb|center|600px|The schematic of the Voltage Controlled Divider. The colors are only there to make it clear.]]
+
[[File:cgs_schem_cgs27_vca.gif|thumb|center|400px|The schematic of the VCA/Wave folder.]]
   
  +
The 1uF capacitor is to reduce any clicks caused though CV bleed-through. The 1M on pin 1 of the tune is really only needed if you do not include the DRIVE potentiometer. While I have specified 50k and 100k pots, the values are not critical. Anything between 20k and 100k would be fine. The tube is not really critical either, though pinouts will vary depending on the tube selected. I chose this tube simply because I have a lot of them.
The Voltage Controlled Divider consists of several distinct blocks, each which is fairly simple in its operation.
 
 
The circuitry around IC1B processes the incoming frequency, and squares up the waveform so it is suitable for the digital portions of the circuit. It drives the counter (4024) and sets the output flip-flop based around two portions of the 40106. This block is fed via a DC mixer stage which includes both inverting and non-inverting inputs, as well as a DC offset allowing for easy adjustment of the "sweet spot" for the incoming signal. The mixer also has an output making the unit a handy utility module even when you are not doing any dividing.
 
 
The output of the counter (4024) is connected to a D to A converter made using an R/2R resistor ladder. The incoming pulse train will step the counter (4024) until the voltage on the output of the D to A converter is greater than that on pin 2 of IC1A, at which point the output of IC1A changes state, putting a HIGH on the HO output, resetting the flip-flop, and triggering a short delay that resets the counter to zero. This clears the HO output back to LOW.
 
 
The flip-flop drives the LO output through a transistor buffer.
 
 
IC2 is dedicated to processing the incoming control voltage. The first part of the circuit is a precession half-wave rectifier, blocking any CV that goes below 0 volts. The second part is used to set the minimum and maximum of the voltage presented to IC1A, as going past either end of the operating range results in either silence or an unpredictable oscillation. (Divide by 0 is NOT very practical!)
 
   
 
== Construction ==
 
== Construction ==
  +
[[File:cgs_pcb_cgs27_tubev2.gif|thumb|center|349px|The component overlay. As you can tell, it is rather generic.]]
 
[[File:cgs_pcb_cgs09_ncom.gif|thumb|center|600px|The component overlay.]]
 
 
There are two unmarked capacitors near the power connector. These can be ignored, or if you prefer, have decoupling capacitors installed in them. Any 100n capacitors would do.
 
 
 
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.
 
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 happy with the board, use wire and parts placement as shown in the following diagrams.
When you are happy with the printed circuit board, construction can proceed as normal, starting with the resistors first, followed by the IC socket if used, then moving onto the taller components.
 
   
  +
[[File:cgs_wire_pcb_cgs27_tube1.gif|thumb|center|400px|Start by putting in the following links. Note that one wire runs under where the tube will be mounted. Test fit the tube socket. The holes may need enlarging, as may a few other holes around the board, depending on the components used.]]
Take particular care with the orientation of the polarized components such as electrolytics, diodes, transistors and ICs.
 
  +
[[File:cgs_wire_pcb_cgs27_tube2.gif|thumb|center|400px|After the wires are done, the components can be installed.]]
  +
[[File:cgs_wire_pcb_cgs27_tube3.gif|thumb|center|400px|Wiring the board to the external components. On the connectors, SW is the switched terminal, SL is for the sleeve connection, and TP is for the tip connection. The pots are displayed as viewed from the front, with the shaft pointing towards you.]]
  +
The tube heater can be powered from 5 to 6 volts DC, as is convenient. It is best if the heater 0 volt wire is not the same wire that is the signal ground, though they should be connected together back at the power supply.
   
  +
The resistors can all be 1/4 watt, and capacitors with a 50v rating will be quite adequate.
When inserting ICs into 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.
 
  +
[[File:cgs_photo_cgs27_tube.jpg|thumb|center|400px|Above view without the tube in the socket.]]
 
  +
[[File:cgs_photo_cgs27_tube2.jpg|thumb|center|300px|Above view with the tube in the socket.]]
== Setup ==
 
 
This module requires setting up. Feed an audio signal into the Clock In input. Monitor the output at HO Pulse Out. With the control voltage set at 0 volts, adjust the OFFSET trimmer until the input frequency equals the output frequency. With the control voltage set at the maximum (15 volts if wired as per the diagram), adjust the SPAN trimmer until you get the lowest frequency possible. If the output stops then back up until you get a signal again.
 
 
{{font color|red|Important:}} The first run of PCBs has a minor error - the voltage follower IC4B (center bottom of the PCB) has its wiring confused. The track between pin 5 and 6 must be cut, as must be the incoming trace that connects to pin 6. This trace is then wired to pin 5, and pin 6 is wired to pin 7. Refer to the PCB/overlay diagram above when correcting the board.
 
 
{| class="wikitable"
 
|+ style="text-align:left"|PCB connections
 
|-
 
| HO||High frequency usage output (fixed pulse).
 
|-
 
| CMP||Clock sensitivity pot. Arrows indicate CCW end, wiper and CW end.
 
|-
 
| MOUT||Clock mixer output (not essential)
 
|-
 
| M-IN||Clock mixer negative input (not essential)
 
|-
 
| M+IN||Clock mixer posative input (use as primary clock input)
 
|-
 
| M+IN||Clock mixer posative input (not essential)
 
|-
 
| LO||Low frequency usage output (follows clock input pulse width. Does not work at high frequency)
 
|-
 
| LA||LED anode
 
|-
 
| LK||LED cathode
 
|-
 
| STUP||Climbing staircase CV output
 
|-
 
| STDN||Falling staircase CV output
 
|-
 
| CVN||+VE supply to "normalized" switch contact on CV input jack.
 
|-
 
| CVI||CV input jack #1 (fed via pot)
 
|-
 
| DIV||CV input jack #2
 
|}
 
 
=== Notes ===
 
* The alternate "*" values on the PCB can be ignored. These are optional to provide a "softer" signal for more sensitive synthesizers.
 
* For a maximum division of 32, leave the two resistors marked with circles off the board and place a link in place of the 100k.
 
   
 
== Parts list ==
 
== Parts list ==
Line 90: Line 35:
 
! colspan="2" align=center|Capacitors
 
! colspan="2" align=center|Capacitors
 
|-
 
|-
| 1n5||align=right|1
+
| 220n||align=right|1
 
|-
 
|-
| 10n||align=right|1
+
| 1uF||align=right|1
 
|-
 
|-
| 100n||align=right|8
+
| 22uF 25V electro||align=right|1
|-
 
| 100n (unmarked/optional)||align=right|2
 
|-
 
| 10uF 25V||align=right|3
 
 
|-
 
|-
 
! colspan="2" align=center|Resistors
 
! colspan="2" align=center|Resistors
|-
 
| 10R||align=right|2
 
|-
 
| 1k||align=right|7
 
 
|-
 
|-
 
| 2k2||align=right|1
 
| 2k2||align=right|1
 
|-
 
|-
| 6k8||align=right|2
+
| 10k||align=right|2
 
|-
 
|-
| 10k||align=right|12
+
| 39k||align=right|1
 
|-
 
|-
 
| 47k||align=right|1
 
| 47k||align=right|1
 
|-
 
|-
| 100k 1%||align=right|18
+
| 680k||align=right|1
|-
 
| 200k 1%||align=right|8
 
|-
 
| 220k||align=right|1
 
 
|-
 
|-
 
| 1M||align=right|1
 
| 1M||align=right|1
 
|-
 
|-
  +
! colspan="2" align=center| '''Tubes'''
| 2k trim||align=right|1
 
 
|-
 
|-
| 47k trim||align=right|1
+
| CV4014 or 6064||align=right|1
|-
 
! colspan="2" align=center|Semi's
 
|-
 
| 1N4148||align=right|9
 
|-
 
| 4024B*||align=right|1
 
|-
 
| 40106B||align=right|1
 
|-
 
| BC547||align=right|2
 
|-
 
| LM358||align=right|2
 
|-
 
| TL072||align=right|2
 
 
|-
 
|-
 
! colspan="2" align=center|Misc
 
! colspan="2" align=center|Misc
 
|-
 
|-
| LED (panel mounted)||align=right|1
+
| PP-ST7-195 tube socket||align=right|1
 
|-
 
|-
| Ferrite bead||align=right|2
+
| CGS27 PCB||align=right|1
|-
 
| 0.156 4 pin connector||align=right|1
 
|-
 
| CGS09 PCB||align=right|1
 
 
|}
 
|}
 
=== Notes ===
 
* Only the 100k resistors in the D/A really need to be 100%, though if you are out buying them, you might as well use 1% for them all.
 
* A 10 to 22 ohm resistor can be used instead of a ferrite bead. If you don't care about power-rail noise, just use a link instead.
 
* {{font color|red|If using a Motorola chip here, make sure it is the MC14024 and not an MC4024, which is entirely the wrong chip.}}
 
 
== 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 ==
 
== See also ==
* [[CGS voltage controlled divider (previous version)|Voltage Controlled Divider (previous version)]]
 
 
* [[CatGirl_Synth#The_CGS_modules|The CGS modules]]
 
* [[CatGirl_Synth#The_CGS_modules|The CGS modules]]
 
* [[CGS parts FAQ]]
 
* [[CGS parts FAQ]]
   
 
== References ==
 
== References ==
* [https://web.archive.org/web/20171219235859f/http://www.cgs.synth.net:80/modules/cgs09_vcd.html Voltage Controlled Divider for music synthesizers.] (archived) by Ken Stone, 2003, with permission of the author
+
* ''[https://web.archive.org/web/20180209234737f/http://www.cgs.synth.net:80/modules/cgs27_tube.html Tube experimenter board for music synthesizers.]'' (archived) by Ken Stone, 2001, with permission of the author
   
 
== External links ==
 
== External links ==
  +
* ''[https://web.archive.org/web/20170614003708/http://cgs.synth.net/tube/index.html Audio Synthesis via Vacuum Tubes]'' by Eric Barbour, 1997, for a more detailed discussion on how a tube VCA works.
 
* [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.
=== Suppliers ===
 
* [http://www.elby-designs.com/webtek/cgs/cgs09/cgs09_vcd.html CGS09 Voltage Controlled Divider], Elby Designs
 
   
 
[[Category:CGS modular]]
 
[[Category:CGS modular]]

Revision as of 18:42, 3 June 2019

Cgs photo cgs27 tube1.jpg

CGS27 the CGS tube VCA wave folder 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 connecting 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.

How to use this module

Connect a signal such as a VCO output to the signal input of the tube module. Feed the output to an amplifier or other signal processing module. Turn the LEVEL pot to maximum. This sets the gain to maximum. When fed an 8V peak to peak triangle wave, the first half of the travel of the DRIVE pot acts as an input level control. The second half of the travel sets the amount of overdrive/wave folding. A DC offset voltage can be added to the input signal via an external CD mixer to allow shifting of the fold point, animating the output signal.

A control voltage can be used to control the output level, in which case the LEVEL pot controls the amount of effect the control voltage has. This signal needs to be above 0 volts to turn the VCA on, though negative voltages will not hurt it. put.

A little on how it works

The schematic of the VCA/Wave folder.

The 1uF capacitor is to reduce any clicks caused though CV bleed-through. The 1M on pin 1 of the tune is really only needed if you do not include the DRIVE potentiometer. While I have specified 50k and 100k pots, the values are not critical. Anything between 20k and 100k would be fine. The tube is not really critical either, though pinouts will vary depending on the tube selected. I chose this tube simply because I have a lot of them.

Construction

The component overlay. As you can tell, it is rather generic.

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 happy with the board, use wire and parts placement as shown in the following diagrams.

Start by putting in the following links. Note that one wire runs under where the tube will be mounted. Test fit the tube socket. The holes may need enlarging, as may a few other holes around the board, depending on the components used.
After the wires are done, the components can be installed.
Wiring the board to the external components. On the connectors, SW is the switched terminal, SL is for the sleeve connection, and TP is for the tip connection. The pots are displayed as viewed from the front, with the shaft pointing towards you.

The tube heater can be powered from 5 to 6 volts DC, as is convenient. It is best if the heater 0 volt wire is not the same wire that is the signal ground, though they should be connected together back at the power supply.

The resistors can all be 1/4 watt, and capacitors with a 50v rating will be quite adequate.

Above view without the tube in the socket.
Above view with the tube in the socket.

Parts list

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

Part Quantity
Capacitors
220n 1
1uF 1
22uF 25V electro 1
Resistors
2k2 1
10k 2
39k 1
47k 1
680k 1
1M 1
Tubes
CV4014 or 6064 1
Misc
PP-ST7-195 tube socket 1
CGS27 PCB 1

See also

References

External links