Can any one explain the specifics of how the Microbrute oscillator works. How does it generate sine / triangle / square from a single oscillator?
The VCO basically creates a sawtooth wave. This is rather common in VCOs ("saw(tooth) core") since you can relatively easily convert them into square and triangle waves. This sawtooth wave is then directed onto three paths for further processing, one of which is (1) the sawtooth wave itself.
Typically, saw to square wave converters (2) check the incoming voltage of the sawtooth wave against a defined threshold - this is called a comparator. They keep their output at zero below that threshold level, and instantly rise it to full output voltage* when the VCO voltage at the input exceeds the threshold level. When the sawtooth wave voltage falls down again, the square output goes to zero* immediately, and so on.
For a triangle wave (3), the sawtooth wave is kind of folded: At half level of the slope, the voltage begins to fall in the same way as it did rise before, leading to a symmetric triangle wave.
So it does
not create three oscillators from one (if it did, you'd be able to create detune, sync, or FM sounds) but just provides three flavors of (still only)
one oscillator.
Schematics including a block diagram of the VCO can be found here:
http://hackabrute.yusynth.net/index_en.php?&arg=4* may be converted into symmetric positive and negative voltages, such as 0 V to + 6 V => -3 V to +3 V
