my (VCO) DIY update

[Tony Clark]

   Well I've finally finished the circuit board for my long-suffering VCO 
project!  It has taken a few months to complete it due to space 
constraints.  My requirements were that the circuit be no more than 3" 
wide and as short as feasible in the vertical direction (came out to 
3.5").
   It is a hybrid SMT and thruhole design which allowed me to mount parts 
conveniently on both sides of the circuit board.  This greatly reduced 
signal path lengths and saved on board space immensely!
   The circuit is a modification of the ASM-1 VCO with RC filters on all 
power pins and precision voltage references for the current mirror and 
other circuitry.  It was done to allow a wide operating supply (12-15V) 
without recalibration.
   The current mirror is a non-heated design that (still under testing) 
is largly unaffected by temperature.  I plan to do extensive testing of 
this design when I get the circuit boards built.
   The board has two 34-pin connectors (17 maximum connections), one for 
inputs and another for outputs.  It also has a third connector for 
accepting a (future) waveshaping board to add an additional 5 waveforms 
to the stock sawtooth, square, and pulse waves.
   I have even included an onboard jumper that will allow a person to 
select either the sawtooth wave or the triangle wave (from the waveshaper 
board) to generate the square wave!  This is because I ended up not being 
sure about how the phase relation of the square wave to the saw/tri waves 
would be applied in a modular setting.
   For instance, by having the square wave generated from the triangle 
wave as opposed to the saw wave will give you the ability to have square 
waves in 0 and 90 degree phase (assuming you leave the pulse at 50%).
   Whew!  Anyway, I hope to receive the boards on Monday and depending on 
how soon the SMT parts arrive, I should have more news later next week!
   My next project will be to design the waveshaping board (assuming that 
I won't need to tweak or redesign the VCO board).  I hope to, ultimately, 
create a series of circuit board "modules" that utilize the same form 
factor so that they can be easily dropped into various projects from 
modulars to poly synths.

   More to come!

   Tony

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I can't drive (my Moog) 55!         |     The E-Music DIY Archive
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Tony Clark -- clark at andrews.edu     | aupe.phys.andrews.edu/diy_archive
http://aupe.phys.andrews.edu/~clark |     Contributions welcomed!
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