Updated : may 6th, 2007 MiniMoog VCF
En français 
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Description

Well, it was meant to be! I could not possibly avoid building a clone of this very successful and famous filter: the Minimoog VCF!
This filter has a sound of its own that contributed to the success of many songs during the 70s and 80s.

My aim here was to design a quite faithful copy of this mythic filter while using components that minimize the burden of selecting a great number of matched transistors. This is why I used cheap transistor arrays (CA3046). As for all the other filters of my YUSYNTH project, I have added an input and an output buffer to adapt this filter to the input and output levels of my modular system.
Because, my power supply standard is +15/-15V, some values of resistors had to be modified.

Schematics


As a matter of fact the +15/-15V version I have designed look very similar to that designed by Yasunori HIRAKAWA . Only some resistor values are different  due  to the characteristics of  the CA3046  transistors.

Printed circuit boards and component layouts

NOTE : the PCB and a component kit for this module are now made available by Bridechamber

PCB - tracks

Component layout





Get the schematic as a PDF file
Get the PCB as a PDF file
Do not forget to solder the two straps, one is located beneath U2 !

Building details
reference
 value
 quantity
U1,U2
 CA3046 Intersil, CA3146 and CA3086 are possible substitutes 2
U3
 TL072
 1
Q1
 BC557
 1
Q2,Q3,Q4,Q5,Q6,Q7
 BC547 matched by pairs
 6
R1,R2
 10 ohms
 2
R25
 22 ohms 1
R17,R19,R20,R21
 150 ohms 4
R29
 180 ohms 1
R14
 220 ohms 1
R18,R22
 330 ohms 2
R12,R15
 470 ohms 2
R34
 680 ohms 1
R16,R28,R33
 1K
 3
R26
 1.2K
 1
R11
 1.8K
 1
R6
 10K
 1
R23,R30
 47K
 2
R5,R31
 56K
 2
R7,R8,R9
 100K
 1
R3,R4,R32
 120K
 3
R10
 150K
 1
R24,R27
 270K
 2
C14
 100pF
 1
C4,C5,C6,C7
 47nF matched to 1%
 4
C13
 100nF
 1
C9,C10
 220nF
 2
C3,C11,C12
 10µF/50V
 3
C1,C2
 22µF/50V
 2
C8
 220µF/25V
 1
T1
 500 ohms 10/15 turn trimmer
 1
T3
 1K trimmer
 1
T2
 10K trimmer
 1
P4
 10K lin
 1
P1,P2
 50K log
 1
P3
 50K lin
 1
P5
 50K reverse audio potentiometer (ALPHA)
 1
Jk1,Jk2,Jk3,Jk4,Jk5,Jk6
 female jack socket
 6
Do not forget to solder the two straps, one is located beneath U2 !
Wiring


Front panel
Panel design
Download the silkscreen mask as a PDF file

Download the silkscreen mask as a JPEG file


Trimming
V/Octave tracking :
  • Apply 0.000V to the V/Oct input
  • Turn the frequency knob fully counter-clockwise in order to measure 0mV at the base of Q1 (node between R46, R30 to R34)
  • Apply 1.000V to the V/Oct input
  • Adjust T1 in order to measure 18.2mV at the base of Q1
  • Apply 5.000V to the V/Oct input
  • Check that you have 91.0mVat the base of Q1, if not adjust T1
  • Apply 0.000V to the V/Oct input
  • Set the filter to auto-oscillation (EMPHASIS turned fully clockwise)
  • Connect a keyboard (CV/GATE) to the V/Oct input
  • Play a tune and check the goodness of the tracking
  • Slightly adjust T1 to achieve a good chromatic tracking.
Frequency range :
  • Apply a sinewave with frequency 32Hz to the audio input
  • Emphasis potentiometer to minimum resonance (fully counter-clockwise)
  • Turn the frequency knob fully counter-clockwise
  • Adjust T2, in order to mute the 32Hz signal.
Emphasis :
  • Adjust T3 in order to reach auto-oscillation near 95% of the full range of the EMPHASIS pot.

References
Here are interesting links where to find schematics and infos about the Minimoog VCF :
  • Jack Palance minimoog site (schematics and PCB layouts)
  • René Schmidtz VCF,
  • Another excellent clone by RadioJunkBox, in Japanese but the schematics and PCB drawings are available
  • Jorgen Berfors' Bergfotron minimoog VCF clone :

The DIY builders' gallery
Here are the photographs of the yusynth MiniMoog VCF modules built by other synth geeks around the world.
Thank you  guys for sending me these nice photos.

Name : Czaba ZVEKAN
Modular project :
Location : Basel, Switzerland
Website :  		Name : Jan CZMOK
Modular project :  Bastelstube
Location : Germany
Website : http://diy.czmok.de
Name :
Pseudo : Etaoin
Modular project : Casia MS01
Location : Utrecht, Netherlands
Website : www.casia.org/modular


The VCF module is integrated in an effect device with an envelope follower
  
Name :
Pseudo : Sebo
 Modular project :
Location : Argentina
Website : http://www.cosaquitosenglobo.com.ar
 Name : Ivan
Pseudo :
Modular project : greta1
Location : Zagreb, Croatia
Website :  		Name : Julien
Pseudo :
Modular project :
Location :
Website : 


Name : François Labarre
Pseudo : Blups
 Modular project :
Location : Amiens, France
Website : http://www.myspace.com/cromthewindingstar

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