Harmonics and Phase

Magnus Danielson e93_mda at drum.it.kth.se
Thu Aug 1 19:23:44 CEST 1996


> It is my understanding that when two waveforms are combined, it makes
> no difference what the phase relationship is as long as it is
> constant.  Is this true only of two sine waves or of any two wave
> forms?  The reason I ask is that I am designing a 'wave folder' and it
> will effect the design.  What I am doing is taking a saw waveform and
> 'folding' it at a setpoint (determined by a CV).  This is done by
> biasing an op amp so that part of the wave is negative and part is
> positive (the bias is really the CV).  Then I diode clip and invert
> this signal.  This is then amplified (variable gain, maybe CVable) and
> added (really subtracted because of the inversion) back to the
> original.  If the gain is exactly 2, and the setpoint is exacly 1/2
> the saw voltage, this would produce a triangle.  Now if phase doesn't
> matter, I should not need to allow adding of the waves as well as
> subtracting.  My question is: will I need to allow for both adding and
> subtracting or just one?

Well... there is several ways to describe this... from a pure electronic point
of view you can add as many waveforms you like without bothering about phase
as long as no two waves share a common frequency... if they do the phase will
play a role (haveing them sligth out of tune creates nice coloring).
This is ture only in systems that are linear most non-linear systems will act
diffrent... think of distboxes etc.).

However, from an listening point of view you can certainly hear the polarity of
a sound over a wide range. For instance, an bass-kick sound diffrent depending
on which polarity you play it in. A positive polarity kick (initial high 
preassure) will sound bassier then oposite polarity... negative polarity will
sound more hollow, it is there but you don't really get it "rigth" however you
turn your EQ's...

What is teoretically true migth not "sound" rigth...

Magnus




More information about the Synth-diy mailing list