Dave Smith Instruments SYNTHESIZERS

Over the years, I've heard of PWM as being a key component to certain 
sounds.  Can anyone elaborate on some suggested uses of PWM on the 
Evolver?  Just some basic settings, what modulators to use and why.

Thanks!

> PulseWidth Modulation
One of Evolver's analog oscillator shapes is a "pulse wave".  A pulse wave  
basically goes immediatly and abruptly from zero to full, stays there,  
then abruptly drops back to zero.  If this sounds like a square wave,  
that's because it IS.  A square wave is a pulse wave where the "on" and  
"off" portions are of equal size/duration.  In other words, all square  
waves are pulse waves, but not all pulse waves are square waves.

Evolver offers a range of pulse waves, with increasingly longer "pulse"  
periods.  At P-01, the pulse period is so short it's basically nothing,  
and at P-99, the pulse period is so long, the "off" period is basically  
nothing.  This is why at the extremes you don't hear any sound...it's like  
the oscillator isn't making a wave at all.

Bring up a basic patch (wide open filter, no modulation etc.) and turn off  
all but OSC 1.  Set it to P-50.  That's basically a square wave.  Now set  
it to P-25.  Sounds a bit different, right?  Now try P-75.  Hear a  
difference between that and P-25?  Think about why.

Evolver, like many classic analog synths, allows you to modulate (i.e.  
change/control/affect) the pulse width with a variety of sources.  The  
most common method is via a simple LFO, because that and envelopes are  
"classic" synth's primary means of modulating ANYTHING.  Let's explore the  
LFO modulation.

Practical Applications:
Since manually changing pulse width results in a change in timbre, one  
would expect a modulated pulse width to produce a regularly  
changing/varying timbre.

In fact, a "classic" analog string sound comes from modulating the pulse  
width of square waves.

Take your basic patch...
Turn off digital oscillators (set level to 0)
Set OSC1 to P-52
Set OSC2 to P-48
Set up LFO 1 with triangle wave, frequency of 25, depth of 25, and  
destination of OSC 1 Pulse Width
Set up LFO 2 with triangle wave, frequency of 30, depth of 15, and  
destination of OSC 2 Pulse Width
Leave the filters off/wide open, give it a not-too-abrupt attack (25?).   
Check it out.  Add some echo and chorus, and boom, you're Gary Numan!

Next, try mapping the Modulation Wheel of your controller to "OSC ALL  
Pulse Width".  Set it to a value of +52.  Hold down a key and start moving  
the Mod wheel up.  What is happening?

Experiment with increasing depth dramatically for one, then both  
oscillators.  Then try increasing frequency the same way.  Try decreasing  
them, too.

The key to making the string sound rich is to make the variation of the  
pulse widths irregular, but not too extreme.  Add a third LFO, also a  
triangle.  Give it a very slow frequency, shallow depth, and assign it to  
OSC ALL Pulse Width as well.

You want to use the triangle LFO because it is the smoothest - the others  
all provide abrupt changes which make the sound less, um, "swirly".

Other things to try:
Clear all other PWM settings.  Map Envelope 3 to Pulse Width All.  Set  
your Oscillators to slightly (or radically) different P-settings.  Vary  
the Envelope 3 settings.

Similarly, try substituting a very slow, synced sawtooth LFO or reverse  
sawtooth LFO for your triangle LFOs.

Try turning off all the LFOs and assigning pulse width ALL to MIDI key.   
Monkey around with the amount of modulation applied and see what you can  
do.

You can also do interesting things by combining PWM (pulse width  
modulation) with hard oscillator sync.

(An expanded version of this will be included in "The Beginner's Guide To  
Evolver")
-- 
Anu Kirk
Musician/Composer/Producer

Thanks Anu!  That's exactly what I was looking for.  Clear, concise, 
and to the point.  I will be doing much experimentation with this 
this weekend (subtlety appears to be the key, as I was trying too 
drastic or fast changes).  Can't wait to see the finished guide, 
sounds like a winner.

  -Yancy


> Many interesting things about PWM
> 
> (An expanded version of this will be included in "The Beginner's 
Guide To  

> Evolver")
> -- 
> Anu Kirk
> Musician/Composer/Producer

Anu,
I found this very helpful in filling out some of the gaps in my 
knowledge. I always wondered about those P1-100 Waveforms! I also 
like assigning the square-wave to the LFO (using pitch, filter,noise 
etc as a destination) while the sequencer is running to spice up 
rythms. Keep up the good work!
Thanks,

Rick 



- In DSI_Evolver@yahoogroups.com, "breakfaster11" 
<breakfaster11@m...> wrote:
> 
> Thanks Anu!  That's exactly what I was looking for.  Clear, 
concise, 

> and to the point.  I will be doing much experimentation with this 
> this weekend (subtlety appears to be the key, as I was trying too 
> drastic or fast changes).  Can't wait to see the finished guide, 
> sounds like a winner.
> 
>   -Yancy
> 
> 
> > Many interesting things about PWM
> > 
> > (An expanded version of this will be included in "The Beginner's 
> Guide To  
> > Evolver")
> > -- 
> > Anu Kirk
> > Musician/Composer/Producer