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Reason's Subtractor and synthesis technique
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fuzzikitten
Annunaki
Started Topics :
40
Posts :
603
Posted : Mar 18, 2004 17:08
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Hello all,
I have been trying to recreate a nice patch I have in Subtractor on my Alesis Ion. I have gotten fairly close but am having a hard time recreating the 'Phase' knob on the Subtractor. I'm not sure I understand what it does fully and was wondering if anyone had any insight to it.
The manual describes the knob as a 'Phase Offset Modulator' that creates a copy of an oscillator's waveform and applies it back onto the oscillator (each oscillator has one of these knobs). Twiddling the knob offsets the copy so that the original wave and the added copy of it are out of phase by how much the knob is turned. In addition, the two waves can be multiplied or subtracted. (more here: http://www.propellerheads.se/products/reason/index.cfm?fuseaction=get_article&article=closeupsubtractor )
I KIND of understand what this is doing on a basic physical level but am having a hard time reproducing this with the Ion. The manual mentions that Pulse Width Modulation can be emulated with the Subtractor using this phase knob.
My plan now is to learn more about PWM and see if that helps to clear things up.
Are there any synthesizer geeks out there that want to give me a basic rundown of PWM and how this phase knob could be used to reproduce it?
Thanks!
-Alex
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ZilDoggo
Started Topics :
4
Posts :
663
Posted : Mar 18, 2004 18:51
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first of all, PWM stands for Pulse Width Modulation,.
a pulse wave is like a square wave., the difference is that a square wave is 50% up and 50% down.,
a pulse wave has other percentages., (for instance 20% up and 80% down)
actually, a square wave is a 50% pulse wave!!!
so a 20% pulse wave is 20% up and 80% down.
what people refer to as the pulse is usually the part that has less than 50% of the wave (the thin bit)., (since the rest of the wave fills in the percentage)
in the case above it's called a 20% pulse and not a 80% pulse., this is because.,
PWM is modulating the width of the pulse.,
so imagine you start with a normal 25% pulse wave .,
if you do PWM then you modulate the 25% setting.,
so, for instance, with a triangle lfo it goes from 25% to 50%, back to 25%, then to 1% and back to 25% again.,
that's all there is to it.,
well, there is also the constant energy thingie but i don't want to get into that .,.,
in reason you can get something LIKE pwm in subtractor if you choose a square wave for the oscilator (forget about osc.2 for now., it works the same as osc.1)
then you need to set the phase mode to subtract (-) .
what you have now are 2 square waves. but one is exactly the oposite ., (so when one is up the other is down)
now, you can imagine that if those two waves were totaly in sync (phase knob at 0) then you would not hear anything (because they cancel each other out).,
but then you can use he phase knob to 'slide' one wave over the other.,
the effect is a sounds like pulse width modulaion., it's not REALY pwm because the result will have 3 distinct levels instead of only 2 but it sounds similar,
it's a bit hard to explain without graphics but i hope you get it.,
you can get a similar effect if you have a synth with two square oscilators and you slightly modulate the frequency of one of them .,.,
hope this helps.,
grts,.,
aka.,
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fuzzikitten
Annunaki
Started Topics :
40
Posts :
603
Posted : Mar 18, 2004 19:37
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Thank you very much! This really helps me understand how I was getting that nice growling sound out of Subtractor.
Apparently what I have is a triangle wave that is phase shifted back on itself so that it cancels out as you describe below. I then have some modulation going on which adjusts the phase setting and in essence 'slides' the two waves back and forth to get the growls.
This is a huge step - now that I know what has to be done I can see if it's possible with the Ion.
Thank you very very much!
*bows*
-Alex |
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ZilDoggo
Started Topics :
4
Posts :
663
Posted : Mar 18, 2004 20:15
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no problemos ,.. 
greets.,
aka., |
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