[PD] frequency shifter

derek holzer derek at x-i.net
Fri Nov 24 17:16:04 CET 2006


hard off wrote:

>>> I would simply use two
> more triangle oscillators in place of the pitch shifters, and set the
> frequencies using a bit of math based on the frequency of the first
> triangle oscillator.<<

> if you could help me with the math required, i would be very grateful.

It's simpler than you might think... Take the number that is providing 
the frequency for the first triangle oscillator and add (or subtract) 
175 and 224 to (from) it and use this number to set the frequency of the 
other two. I'm not sure which direction the frequency shifter is 
supposed to go in this diagram, so try either adding or subtracting. 
Also what is not clear is if the original triangle wave is heard in your 
diagram, or only the two pitch shifted ones, so either you will only 
hear the frequency-shifted pair or you will hear all three mixed with 
your two sinus waves.

[number box\   <---set master frequency
|      |          |
|     [+ 175] [+ 224]  <---set shifted frequencies
|      |          |
|      |         [triangle~]
|     [triangle~]
[triangle~]

Where [triangle~] is an abstraction you have made which produces a nice, 
bandwidth-limited triangle wave ;-)

If my cheap ASCII art doesn't come through, let me know and I'll be less 
lazy and patch it...

Hope this is clear enough,
d.


-- 
derek holzer ::: http://www.umatic.nl
---Oblique Strategy # 112:
"Magnify the most difficult details"




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