Doepfer

--- In Doepfer_a100@yahoogroups.com, "omegaattraktor" 
<omegaattraktor@...> wrote:
>
> --- In Doepfer_a100@yahoogroups.com, "Monroe Eskew" 
<monroe.eskew@> 
> wrote:
> >
> > That sounds like thru-zero amplitude modulation, which is 
nothing new,
> > though it is a nice feature to put within one module.  But thru-
zero
> > frequency modulation?  Still confused.
> 
> 
> negative frequencies has nothing to do with inverted phase. it 
means 
> that the signal is going its way back. but of course the time 
continuum 
> will not be affected. this can happen at any amplitude of the 
signal, 
> therefore it doesn't invert the phase.
> 
> negative frequencies do occur with large amount of fm. imaginge 
the 
> frequency of an osc with 1kHz is modulated by another osc. if the 
> amount of modulation is increased there is a point when the 
frequency 
> is modulated between 0kHz and 2 khZ. if you increase the 
modulation 
> further the frequency finally goes to negative. thru-zero fm just 
means 
> that an osc can handle this.
> 
> regards,
> oliver
> 
> http://www.namshub.ch/


exactly. a standard vco will stop oscillating at 0 hz,
it even cannot reach 0 hz at all because of technical issues
within the vco design. a standard vco can never have more
than 100% linear fm.

a thru-zero vco can handle more than 1000% linear fm, because
it can go "through" that 0 hz barrier into "negative" frequencies, 
which means that the waveform reverses direction, not it's phase.
it's a bit like driving a car in reverse gear.

example, a vco sinewave cycles between +5 and -5. lets say that at
one given point the waveform has an amplitude of +1 volts
and is on its way down, towards -5 volts. when the thru-zero vco
reverses direction at that given point then the waveform will
continue at +1 volts amplitude, but going up towards +5 volts.
while the facts are quite boring, the sonic differences are huge.

best wishes

ingo