Adventures with the Tilman modulator

[Chris Crosskey]

Hi Folks...

IIRC the Elektor VCO had a pulse-modulated Sawtooth......I'll try to dig it 
out.....surely you are better off using acomparator and a FET....when the 
comparator says you are higher than X the FET <conducts>...you might be 
better opff with a CMOS/Audio switch chip for an LFO though....duty mod by 
cahanging the comparator bias voltage.....feed it a saw-tooth instant PWM 
saw...could do th esame with a triangle or a sine come to think of it....

chrisc


>:::Well, the final results are quite spectacular. The duty cycle can be
>:::changed from about 10% to 90%. I'm going to be using it in a VCLFO, but
>:::it sounds quite good. When you modulate with another LFO, the sound is
>:::similar to PWM but not quite. There is also a pronounced change in
>:::pitch, more of a phase change I think.
>
>I'm confused...
>
>AFAIK the Tilman proposal is a post processor, i.e.. rides on a
>saw given by an independend vco. Thus I can not understand why
>you hear a pitch change, ... ahh, say measure a frequency change.
>There should be no frequency change at all, until the circuit
>fails due to overload. 
>
>Pitch is not frequency...
>
>Is it possible that the changing spectra lead to a changing pitch
>sensation? What do you mean by phase change?
>
>And what happens if you cross the 10% (or 90%) border?
>I guess the wave form gets confused then...
>
>m.c.
>
>
>
>.