2. It Starts with the Oscillator

  The longest journey starts with a single step.  I knew this was an ambitious project and that it may never be complete.  So I decided to just take one step at a time.  For me on this journey that first step was the voltage controlled oscillator (VCO), the core of any subtractive analog synthesizer.  So I began researching VCO circuits.

  Electronic synthesizers began taking off in the 70's, and incorporated many circuits that have been around even longer than that, so VCO circuits are nothing new.  Not only is there plenty of circuit info available on the 'net, I found there's quite an active community for DIY (Do It Yourself) modular synth's and eventually came across a fantastic website by DIY synth enthusiest Yves Usson, yusynth.net.  On this site Yves shares with us many excellent designs complete with schematics and layouts.  His VCO circuit sounded like a great place to start, especially since he provide a layout.  All I had to do was order the parts (I use mouser.com) from the parts list, print out the layout and etch the board (there are many tutorials online about how to etch your own boards so I won't go into that).

  The designs on yusynth are intended to be used in a modular synthesizer, which is not exactly what I wanted.  As the title of this blog states, I set out to build an integrated synth as I wanted something more compact and less cumbersome.  An 8 voice modular unit is quite a beast and while the routing options of an integrated synth are more limited I felt the routing utilized in the Jupiter would be sufficient for what I wanted.  Even though the yusynth designs are "modular", the circuits are very similar to the sections that make up an integrated synth, all I had to do was integrate them.

  But I'm getting ahead of myself, back to the VCO.  I took the first step and built a single VCO board not really knowing what to expect, and figuring if it didn't work out it was only a few bucks and not a big loss at this point.  After some trouble shooting (only my second DIY PCB) I was pleasantly surprised with the result.  It sounded great!  At least for a single oscillator with no filter or envelope control or keyboard etc.  It wasn't anything fancy, it's just and oscillator after all.  All it did was produce a constant tone whose pitch I could vary by twisting some knobs.  But as a base to start building up from, I was very happy.