Dual Oscillator

Video Tutorial

Project Summary 

The Werkstatt features a single-oscillator VCO, but by patching and attenuating our keyboard control voltage to our LFO we are able create a second oscillator.  This feature is best used to add a lower frequency Triangle or Square wave.

3D Printing


1 x 6.8kΩ Resistor

2 x 10kΩ Potentiometers

Jumper Cables

1 x Breadboard



To hear our LFO signal clearer we will need to patch the VCF OUT to the LFO OUT.  However, if we do this without any resistance the LFO signal can be overpowering and distort our output signal.  Therefore, we will need to place a 10kΩ potentiometer in between these pins to act as a variable resistor. See figure 1 for a connection diagram.


Figure 1. 10kΩ potentiometer in between the VCF OUT and LFO OUT. 


Now if we play a note on our Werkstatt we will hear the LFO frequency, that is if the RATE knob is turned clockwise far enough to push the LFO into the audible frequency band.  However, you will notice that the LFO frequency does not change depending on what note you hit, to add this functionality we will need to patch our KB CV OUT into our LFO IN.  If we do this without any additional components the tuning will be off so we must add a 6.8kΩ resistor and 10kΩ potentiometer to ensure proper tuning, figure 3 provides a small schematic of these components and their orientation.  See figure 2 for a better look at the exact jumper connections.  You will notice that we need to pull ground from the Werkstatt.  This can be done by connecting to any screw terminal. 


Figure 2. Final jumper configuration.


Figure 3. KB CV OUT to LFO IN schematic. 


Once our connections match those of Figure 2 we are ready to tune our LFO and VCO together.  Notice that the 10kΩ potentiometer acts in a similar manner to our KB CV TRIM pot that is located on the Werkstatt's PCB.  This means that if the octave of our LFO seems a little off, simply adjust this pot to tune.  This will need to be adjusted if you switch between a low frequency LFO setting to a higher one.  Once our VCO and LFO are in tune both with eachother and within their octaves your mod is complete and you now have a second playable oscillator available on your Werkstatt.



This project also comes with 3D printer files to print your own housing.  See figure 4. for a 3D rendering of the top and bottom panels for this housing. 


Figure 4. Dual Oscillator 3D printed housing render. 



  Fritzing is an open source visual breadboarding software.





MakerBot creates desktop 3D printers and scanners for professionals and the home. 


Push Button Vibrato
555 IC - 2nd Oscillator