This is my extended version of the Trapezoid VCO core designed by Don Tillman. My first implementation for a 15V banana system with separate waveshaper can be found here. My second implementation for a 15V banana system with integrated waveshaper can be found here.This time I moved on to the 12V Eurorack format. The core is still based on the original design from Don (used with permission). I found the original article and schematic about the Trapezoid VCO on Don Tillman’s site (Link to original article from 19 July 2003). The article consists off three parts with the core implementation in part 2. I kept the basic idea and changed nearly everything else. I use an other exponentiator scheme and temperature stabilization. Another reference voltage device is used. A octave switch is added. And quadrature square outputs are implemented. As well as the additional waveforms triangle, sine, ramp up, ramp down and pulse.
For the extended Version I added the two missing outputs for ramp up, ramp down and pulse. Now this VCO has all the usual wave outputs, all 90deg apart.
Specs and features
- Trapezoid quadrature output
- Square quadrature output
- Triangle quadrature output
- Sine quadrature output
- Pulse output, 0deg, 90deg, 180deg, 270deg
- Ramp up output 0deg, 90deg, 180deg, 270deg
- Ramp down output 0deg, 90deg, 180deg, 270deg
- Octave switch
- Through zero modulation
- PWM input for 0deg, 90deg, 180deg, 270deg pulse
- V/Oct, FM log and trough zero CV input
- Temperature compensated
- Fine frequency setting
- Runs on +/-15V and +/-12V
- Power consumption around 150mA each rail
There are to much schematic to post here. Please refer to my website. Only pictures here.