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