CESYG DUALFO, Инструкция по установке и эксплуатации, Страница: 19 / 32

Now take a look at the phase diagram (end of manual). An arrow at the 90 degree
position lies between the 0 degree and 120 degree arrows, so we need some mix of
these two sine waves to produce the required 90 degree one.
As the 90 degree arrow is closest to the 120 degree arrow we start with 100% of the
120 degree sine wave. Then, note that the 90 degree arrow crosses the dashed horizon-
tal line - this corresponds to the 0 degree sine wave. As it crosses the middle this
shows that we need half, or 50%, mix of the 0 degree sine wave. Finally, also see that
the length of the arrow from the centre to where it crosses the dashed line is about
87% of the full length. This tells you the amplitude of the result: about 87% of the full
scale signal (about +/- 4.3V).
If all this sounds complicated, it really isn’t! Try it for yourself with a pencil and ruler.
After a couple of minutes you will soon master this technique! And then you will be
able to synthesize two sine waves with
any phase offset you want. You could also use
three VCAs ( e.g. , three-channel VCA mixer) so that the synthesized sine wave is under
full voltage control.
Video Synthesis
With three phase-locked outputs the main LFO is ideal for modulating the red, green
and blue components in video synthesis. The auxiliary LFO can then be used to
modulate the main LFO to introduce further colourful modulations, perhaps synchro-
nised to some visual trigger or some multiple of the frame period.
CESYG DUALFO USER MANUAL
Page 19