Updated : sep 29th, 2013 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.

I recently modified the PCB drawing in order to provide PSU connectors for Synthesizers.com, MOTM and Eurorack.

NOTE: for Eurorack a pair of jumper must be add and the values of resistors R24,R26,R27 must be changed.

Schematics




For Eurorack R24 and R27 must be changed to 220K et R26 to 1K

Printed circuit boards and component layouts

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

PCB - tracks

Component layout




Dotcom/MOTM version


Eurorack version


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 !
Eurorack version don't forget the additionnal straps, and change the values of R24,R26,R27 as indicated in the BOM

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* for +15V/-15V PSU 1K for +12/-12V PSU
1
R11
1.8K
1
R6
10K
1
R23,R30
47K
2
R5,R31
56K
2
R7,R8,R9,R13
100K
4
R3,R4,R32
120K
3
R10
150K
1
R24*,R27*
270K* +15V/-15V PSU 220K for +12/-12V PSU 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 R9 to R11)
  • 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
Name :
Pseudo : Sebo
Modular project :
Location : Argentina
Website : http://www.cosaquitosenglobo.com.ar
Name : Julien
Pseudo :
Modular project :
Location :
Website



Name : Zarko
Modular project :
Location : Gardanne, France
Website :
Name :
Pseudo : Tudy
Modular project : Yusynth 17U
Location : Brno, Czech Republic
Website :www.insania.freemusic.cz
Name : Steven Brenner
Pseudo :
Modular project :
Location : Waterloo, Ontario, Canada
Website




Name : Peter Hostermann
Modular project :
Location : Germany
Website : http://www.peter-hostermann.de


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