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Author Topic: Waveforms  (Read 768 times)

studio139

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Waveforms
« on: September 10, 2013, 09:09:49 am »
I realize this may be a novice question, but can anyone explain how the Minibrute can produce the saw, square and triangle waves and blend them from a  single oscillator?  I know this could be a complex answer, but I understand how the Moog oscillator(s) can be variable, the Minibrute is more like the oscillator(s) on a Prophet, where you could blend the various wave shapes, which always confused me as to exactly how it worked.   

tertior

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Re: Waveforms
« Reply #1 on: September 10, 2013, 09:05:59 pm »
That is in the assembly of the oscillator which is added diodes, resistors capacitor, which can achieve various types of waves.
it is an image because it is much more complicated

Mmarsh

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Re: Waveforms
« Reply #2 on: September 12, 2013, 01:21:01 am »
Please correct me if I'm wrong, but the oscillator only produces one waveform (can't remember if this is a saw or triangle) - this is split into three more signals which take the 'native' waveform and transform into the target waveform with some circuitry. These are then sent to the mixer which you control using the waveform sliders. Some of the waveforms have further processing available like the ultra saw and the metalizer.  Hope that helps!

beefinator

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Re: Waveforms
« Reply #3 on: September 12, 2013, 03:50:49 am »
Please correct me if I'm wrong, but the oscillator only produces one waveform (can't remember if this is a saw or triangle) - this is split into three more signals which take the 'native' waveform and transform into the target waveform with some circuitry. These are then sent to the mixer which you control using the waveform sliders. Some of the waveforms have further processing available like the ultra saw and the metalizer.  Hope that helps!

It's probably mostly like that.  Some base waveform oscillator, that is fed through waveshaping circuits.
It just depends on what the base waveform is.

I think I've seen somewhere that the base oscillator is a sawtooth.  So the sawtooth is fed into the ultrasaw delay/phaseshifting circuit.  But it also goes to the square wave shaper, which is a very simple circuit that uses a comparator to compare the current voltage of the sawtooth to some threshold (turning on only when it's above the threshold).  Adjusting this threshold gives you PWM.

Then there's the triangle, which I don't know exactly how it does it, but it takes the sawtooth and turns it into a triangle, then runs it thru the wavefolder circuit of the metalizer.

Then there's the suboscillator, which (again, I'm not sure how) just divides the frequency by 2.  Perhaps there's a circuit that takes the pulses from the squarewave and divides it by 2 or 4 (-1 or -2 octave).  This can be easily done with a circuit that toggles on and off every cycle of the squarewave.  (two of those in a row for the -2 octave).  Then my guess is that the resulting octave(s)-down squarewave is shaped into a sine wave.  That could explain the little blip in the sine wave, meaning it's not a perfect waveshaper (I'd imagine it's not trivial removing all the overtones of a squarewave).

my thoughts.   :D
Never really thought about this before.   But it's kinda fun to ponder on it.

Mmarsh

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Re: Waveforms
« Reply #4 on: September 12, 2013, 06:34:02 am »
Yes, exactly what I was thinking!

tertior

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Re: Waveforms
« Reply #5 on: September 13, 2013, 11:42:17 am »
Oscillator is a sine , relaxation or astable. With a oscillator sine you get a sawtooth for exemple.

yusynth

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Re: Waveforms
« Reply #6 on: September 16, 2013, 11:30:44 am »
The oscillator on the MiniBrute like on many systems produces a balanced sawtooth signal (balanced here means swinging between negative and positive voltages), the other signal are built from this sawtooth, for example the square-pulse signal is obtained by thresholding the sawtooth and the triangle is obtained by rectifying the sawtooth (rectifying means changing the sign of the negative voltages of the sawtooth).
Then you can blend these signals through the mixer to create other wave shapes.

Mmarsh

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Re: Waveforms
« Reply #7 on: September 17, 2013, 01:15:47 am »
Thank you for the clarifications, Yves!


 

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