Introduction

Randy Gordon - Sun Victoria SE randyg at Canada.Sun.COM
Tue May 30 19:50:39 CEST 1995


Hello all,

For those who don't know me (everyone), I will introduce myself.

My name is Randy Gordon and I live in Victoria, BC, Canada. My expertise 
is primarily in software and systems integration, but I do dabble in the 
odd electronics project.

One of my favorite recurring interests is analog synthesizer 
construction.  I have the Electronic Music Circuits book by Barry Klein, 
copies of the Elektor Formant articles, and copies of Electronotes circa 
1972-1977.  For some time I have been wanting to build various circuits and 
I have recently undertaken to build a discrete VCO circuit that appears in 
Barry Klein's book.  I have built simpler circuits in the past, a number of 
guitar effects from Craig Anderton's book, but this is the most complex I 
have attempted to date.

I am currently in the process of designing a PCB layout for the VCO 
circuit. I'm using the shareware PADS schematic and PCB layout software, 
so I'm limited to 30 components at a shot.  I have decided to break the 
circuit into logically seperate modules - Exponential Convertor, Thermostat, 
Oscillator, Saw, Triangle, Square, and Pulse.  I've finished the PCB 
layouts for the Exponential Convertor, Thermostat, and Oscillator modules.
Even with the PCB layout software, it is still a lot of work to place the 
components optimally to achieve a nice trace layout on one side of the 
board. The output from my laser printer looks great, is to scale, and 
should work nicely in the etching process.

I should be finished all the modules shortly, and I should be able to 
etch a board using a friend's UV equipment.

Assuming everything works, I am willing to share the work I have done 
with anyone who is interested.  If I can sustain my own interest in this 
project I should be finished in a month or so.

If anyone has played with some of the discrete VCO circuits in Barry's book, 
I would appreciate any comments anyone may have on the following:

1) I'm building the circuit using a CA3086 transistor array
   for the exponential convertor and thermostat control.  As far as I can 
   tell this should be an acceptable substitute for the CA3046 used in 
   the book.

2) Can high-performance audio op-amps like the NE5230 and NE5532 substitute 
   for op-amps like LM301, LM307, and LF356 used in the book?

Thanks in advance for any insight you may have. I look forward to some 
interesting reading on this list!

Randy Gordon



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