Aries Archive [sdiy] how to build a cv keyboard

[Scott Stites]

On Thu, 12 September 2002, Seb Francis wrote:

> However, I personally wouldn't advise anyone just starting out to build their
own
> keyboard right away.  It's a big project, and you might be better off spending
> your time making some VCOs + VCFs and things :)  You can pick up a second hand
> MIDI keyboard really cheap.  MIDI to CV converter will set you back a bit more
> (e.g. £100 for a basic pre-built Kenton).  

Yeah, I actually didn't worry about a keyboard when I started.  I started with
filters, VCA's, LFO's and a little Yamaha keyboard that I amped up to 10Vp-p.  At
first I controlled the VCF and VCA with an LFO or just a pot to see how they
sounded.  Later, I breadboarded a sample and hold.  Then I got into the delay
module tangent for a while.  Then I built a signal to gate/trigger circuit and an
envelope generator. 

Once I got comfortable with all of the basics, I went for the VCO, Rene Schmitz's
wonderful VCO3, and controlled that with a pot.  Then I tired of that and wanted
to control it with a keyboard.  My little Yamaha has MIDI, but I had all the
parts already for the digital keyboard.  So I got an extremely cheap little 37
note keyboard, stripped all of the components off, hacked and slashed it with an
exacto blade, soldering iron and bus wire into a switch matrix, and breadboarded
the keyboard circuit.  I solder for a living, but it was still good practice to
make all those tiny little connections with 26 gauge bus wire.  The circuitry
itself I will put into a project box.  Functionally, the circuit itself is a
keeper, I love it.  The little keyboard is great for piddling around and
experimentation, but its keys are really too small for 'performing'.  That's OK,
I'll just find a bigger, better keyboard and knock it into a matrix if it isn't
already in a matrix setup, and hook it into the project box.  

Long story short - don't start off with building a keyboard.  There's no payoff
at the end of the project if you don't have anything to drive with it - you just
get to watch it do its thing on an oscilloscope.  It'll take so long, you may
just lose interest before you get to the fun stuff.  A filter - (and I'm not
talking about ladder filters at first - just OTA based Sallen-Key filters) - now
that's instant gratification (fun!!!) as long as you have anything to feed into
it (a guitar, a mini-keyboard, your function generator - anything).  The VCO
should always be approached with great respect, after you feel you've mastered
the less touchy things.

The down side for me is that I'm having too much fun - I spend more time playing
than I spend actually *building* the synth....

Take care all,
Scott

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