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Simple square-saw shaper?
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author Simple square-saw shaper?
Blackened Justice
Hey, I'm about to build a MFOS WSG, and already have a number of mods planned. Is there any simple square-saw waveshaper I could consider implementing?
gde
unfortunately... square waves dont include any timing information; they are either up or down. a 0-5 volt sawtooth is easy to derive other waveforms from. if the voltage is at 2 volts, it is 2/5ths of the way through one cycle...
so you cant exactly convert a square to a saw

but if you look here
http://www.cgs.synth.net/modules/cgs21_super_psycho.html
youll see the oscillators are also based off a 40106
if you grab the voltage at the input of the CMOS inverters and buffer them then you have a triangle(ish) wave for the oscillator
Blackened Justice
Yeah, I know about that triangle-ish wave, I'll and put triangle/square selectors for all three oscillators. So is it easier to turn a triangle into a saw than a square into a saw? If so, then could you please direct me to a simple tri-saw shaper?
A Dingleberry Monstrosity
square waves dont include any timing information? WHat does that mean? seriously, i just don't get it
Clocks are square waves, beyond that I have no idea what "timing information" you could get from a triangle or sawtooth wave.


run it through some kind of integrator, done. Only issue is being able to get it to work perfectly for a range of frequencies and reset to zero after a cycle.
frijitz
A Dingleberry Monstrosity wrote:
square waves dont include any timing information? WHat does that mean? seriously, i just don't get it
Clocks are square waves, beyond that I have no idea what "timing information" you could get from a triangle or sawtooth wave.

Hmmm ... the meaning seems pretty clear, really. After the square wave (or pulse, for that matter) signal goes high, you have no knowledge of when it is going to go back to low, since it is constant as a function of time. A wave with a ramp or other continuous variation changes with time, so if you know the amplitude you know the time. For example, when a ramp wave is at half of its peak value, it is also half way along its period.

You can put a square wave through an integrator, sure, but its amplitude varies as 1/frequency. You could level this with an AGC circuit, but there would be a time lag -- at least as long as the full period. Another way of saying that you need timing information that the square wave doesn't have.

grin

Ian
A Dingleberry Monstrosity
oh!!! OK!

now Im on the trolley, thanks for explaining!
Blackened Justice
Thank you for the insight on why it would be quite difficult to implement wink

Now, I have some other questions:
1) Why does the oscillator circuit use inverting Schmitt triggers instead of inverting comparators? Wouldn't the use of comparators make it much easier to implement PWM?

2) Would sync be possible if I do it like it's done in this circuit: http://www.electro-music.com/forum/topic-23878.html ?
Blackened Justice
[img]http://experimentalistsanonymous.com/diy/Schematics/Full%20Synths %20Drum%20Synths%20and%20Misc%20Synth/Square%20to%20Saw.bmp
[/img]
Couldn't I use this circuit? Is this how they did it in the vintage divide-down string-machines? My interest is not generating a clean saw, just getting some even harmonics in the machine wink
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