8080-VCO

Saw core VCO for Eurorack Modular synthesizers

Summary

This is a full featured SAW Core VCO. Sine, Pulse, Saw waveforms available with multiple modulation inputs and oscillator sync.

All waveforms are derived from a simple saw wave core using a JFET.

This VCO is compact, filling an 8HP space, but has comfortably spaced front panel controls for ease of operation.

Features

• Saw core VCO
• Pulse, sine and sawtooth waveforms
• 1V/octave input + variable Linear FM CV and variable Exponential FM CV
• Adjustable pulse width and variable PWM CV input
• Hard sync input
• Easy to calibrate and customize
• Only 3 ICs
• Accurate tracking and excellent temperature stability
• 8HP Eurorack with our panel

Documentation

Comprehensive documentation, parts lists are provided in the documentation link for building, testing and calibrating the module.

A note on accuracy

If you want a highly accurate tracking VCO, please ensure you use very well matched transistors and also glue the thermistor and the two transistors together. The slight differences in temperature coefficients of the transistors can make the oscillator difficult to tune. If you don't need a highly accurate oscillator, you can use any transistors and even use a resistor instead of the thermistor. Here's a comment from one of our builders of a similar VCO:

"I ended up swapping the transistors from some I got in a Mouser order
vs the ones I matched from a Chinese retailer. Found some that matched
less then 1mv difference and Low and behold, I can tune it now!" From Dayne, Grand Forks, BC.

Demos

The following video, courtesy of Randy Piscione, shows the VCO in action:

8080-VCO used in patch with SEM