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2 Linear Voltage Controlled Oscillators (VCO)

I found two old sketches for two VCOs. Don’t know the creator (not me). I transfered them in LT Spice and played a while until i had a working simulation.I don’t know if these schematics will work in real live but i will build them up on breadboard and will do some measurements.



Sweep 125mV – 1V

VCO1 SAW output



VCO2 Schematic

Sweep 125mV – 1V

VCO2 SAW output


UPDATE 01.01.2014

Built both VCOs on breadboard



Output VCO 1

VCO1 500mV


Output VCO 2

VCO2 500mV


I used an op07 for the input Stage and an TL072 for the oscillator part. The charging cap was 22nF foil.

UPDATE 02.01.2014

I added a third VCO schematic (Korg Style Trident/Polysix). won’t run in LT Spice but i will build on Bread board tomorrow.

Here is the VCO3


UPDATE 03.01.2014

I have built VCO on Breadboard but i changed some cap values:

C1 =4.8nF Styroflex

C3 = 33nF

I used +15 V instead of +5v

I put the oscilloscope probe to the emitter of Q2 for the saw waveform and on the emmiter of Q3 for the pulse output.

The oscillator runs but, a higher negative control Voltage results in a lower frequency.

Have to do some investigations here.

Here some Pics.


Here you can see a constant 15 µS step at the saw wave. The Yamaha CS oscillator has a 30µS step. The schematic looks similar to the Yamaha IG00153 chip!

Saw ouput with -8V CV

VCO3 -8V


Saw output with -4V CV

VCO3 -4V


Update 05.01.2014



will be continued…

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