[sdiy] Dual VCO mixing. / first synth DIY project.

[Scott Gravenhorst]

There is good info in the datasheet and appnotes, both
are available on the net (if you can't find them, email
me, I have the PDFs).  As a straight LFO, the appnotes
have a circuit for an audio oscillator that varies freq.
with a pot.  This circuit is fairly simple and all you need
to do is make the timing cap larger for an LFO.  The sheet 
says the low end is 20hz.  So, make the cap 100 times larger
and you go down to .2 hz, 1000 times and you have .02 hz.

Making it voltage controlled is possible, but the circuit
is more complex and IHMO overly so for an LFO.  Really, the 
ONLY good thing about this IC is the multiple waveform outs.

BTW, this part makes a crappy VCO for music since it is not very
linear.  It can be used as the VCO in a PLL as long as you don't
need the tracking voltage, but rather just to produce the multi
waveforms locked to an input signal.

"Bill Keys" <controlkeys at hotmail.com> wrote:
>>From: cacofone <pulse8 at goodtimetribe.com>
>>Magnus,
>>Gonna get started on making some VCO's and go from there. Can you suggest a 
>>VCO schematic that's versatile and not that terribly hard for a beginner, 
>>or is the one there
>>recommended? I'd really like to have at least triangle, square, and I 
>>really want sine, even though I know, yes, tri/square are easiest, and 
>>perhaps I can add the sine in later after I've implemented square.
>
>Which makes me think of a question I've been meaning to ask... Does anyone 
>know of any VCO (or, if not, LFO) designs (and where the schems might be 
>obtained) based on the (old, but still for sale at the 1974 price) Intersil 
>8038 VCO chip? If so, that chip does sine (and triangle and saw, I think) 
>and might help both cacofone and I  ;o).
>
>>Any advice is greatly appreciated.
>>
>Ditto!
>
>+_+_Yes, honey, I know there are 25 boxes of electronic junk cluttering up 
>the attic. They will, one day, magically be transformed into a modular 
>synthesizer cluttering up the attic.... www.mp3.com/OriginalSimulacrum _+_+
>
>
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