Is the PWM effect similar to the other brands...NO..it's the SAME!
Every analog synth VCO out there with a pulse output (fixed width or
varaible) is created with a comparator of some sort. One might argue
that the type of comparator used will have an effect on the quility
of the pulse generated but I say this...
Consider a square wave (a symetrical pulse where the time high is
equal to the time low). In that pulse there is ideally a perfectly
flat top, a perfectly flat bottom, and two verticle edges that rise
and fall almost instantaniously. The most common "ERROR" in a
comparator is it's lack of speed. That is to say the verticle edges
are not instant but instead have a slope to them. If we took this to
the extreme the two slopes would meet at the top and bottom (leaving
no "flats") and you would be left with a triangle wave. As you may;
or should know, a triangle wave has the SAME harmonic content as a
square wave (odd harmonics only) but to a lesser degree (quieter).
THUS.... a bad comparator will have a slightly lower harmonic
content that an IDEAL comparator but since you'll MORE THAN likely be
processing the wave through filters or EQ, those minor losses will
for the most part be irrelivant.
Before people jump up and down and say, what about overshoot,
crossover distortion, ripple etc. Yes some comparators MAY have other
irregularities etc, but their overall impact is relatively small and
in this particular case the Serge comparators are pretty good.
Bottom line...chuck your wave through a comparator, bung in a little
LFO into the other input and "Bob's your Uncle" PWM. As good as any
other synth!
Hope that little ramble helps clear things up.
Cheers...Dean.
Every analog synth VCO out there with a pulse output (fixed width or
varaible) is created with a comparator of some sort. One might argue
that the type of comparator used will have an effect on the quility
of the pulse generated but I say this...
Consider a square wave (a symetrical pulse where the time high is
equal to the time low). In that pulse there is ideally a perfectly
flat top, a perfectly flat bottom, and two verticle edges that rise
and fall almost instantaniously. The most common "ERROR" in a
comparator is it's lack of speed. That is to say the verticle edges
are not instant but instead have a slope to them. If we took this to
the extreme the two slopes would meet at the top and bottom (leaving
no "flats") and you would be left with a triangle wave. As you may;
or should know, a triangle wave has the SAME harmonic content as a
square wave (odd harmonics only) but to a lesser degree (quieter).
THUS.... a bad comparator will have a slightly lower harmonic
content that an IDEAL comparator but since you'll MORE THAN likely be
processing the wave through filters or EQ, those minor losses will
for the most part be irrelivant.
Before people jump up and down and say, what about overshoot,
crossover distortion, ripple etc. Yes some comparators MAY have other
irregularities etc, but their overall impact is relatively small and
in this particular case the Serge comparators are pretty good.
Bottom line...chuck your wave through a comparator, bung in a little
LFO into the other input and "Bob's your Uncle" PWM. As good as any
other synth!
Hope that little ramble helps clear things up.
Cheers...Dean.
--- In SergeModular@yahoogroups.com, "cuari7" <medejd@t...> wrote:
> Is the PWM effect obtained from these modules similar to the
> conventional pulse-width modulation found in vco's like MOTM,
> dotcom, Doepfer, etc..? In other words, will it give a nice,
> phasing, chorused effect?
>
> Let me know, gang!