[sdiy] 1.0 kohm "tempco" for VCO / sub octave question

[Dave Magnuson]

At 12:38 PM 3/2/04 EST, WeAreAs1 at aol.com wrote:
>
>
>In a message dated 3/2/04 7:40:25 AM, debus at cityweb.de writes:
>
><< You can also add the original saw and the suboctave square to get a 
>suboctave saw. Just an opamp and three resistors.
>
>Ingo
> >>
>
>Hello Ingo,
>
>If you simply combine the original saw and a suboctave square, you get a
wave 
>that's not really saw-shaped, isn't that correct?  Isn't it more like a 
>sawtooth superimposed on a square?  Or am I not clear on the method you're
using?  
>I would love to be able to get a very pure sawtooth suboctave by some simple 
>method.
>


I can see the logic behind this method.  The suboctave is "high" every
other cycle of the sawtooth wave.  

cycle 1: saw on top of a pulse.
cycle 2: saw by itself 
cycle 3: saw on top of a pulse.
cycle 4: saw by itself 

So if sawtooth amplitude is the same as the suboctave amplitude you should
essentially get a sawtooth at 1 octave down.  I tried to make an ascii
diagram below.  I filled the suboctave pulse with "x" to make them stand
out.  

 |\      |\
 | \     | \
 |  \    |  \
 -----   -----
 |xxx|\  |xxx|\
 |xxx| \ |xxx| \
 |xxx|  \|xxx|  \
--   -----   -----

Hope this helps,

Dave Magnuson

Resonant Frequency:
resfreq at hoohahrecords.com
http://www.hoohahrecords.com/resfreq/index.html
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