About
First actual module of the CrapRack system, the OSC CORE, is a hex improved squarewave VCO bank. Each VCO has a pitch control, a hard-stop input (the VCO stops oscillating when a high voltage is present on that input), a pitch CV input, and a squarewave output. It's built around the famous CD40106 and follows the design of the Dronelab VCOs in a way, but i redesigned it a lot, and unlike lots of other VCOs, mine outputs a perfect 50% duty cycle squarewave and has quite a huge pitch range. Given the fact that you can build six simple functional VCOs off one 40106, three 4013s and some passives AND that requires unipolar power - this is a perfect beginner project, even in a standalone box. These things can modulate each other and it quickly turns into a sharp harsh noise mess.
Schematic
The way it works is pretty simple and you can learn more about it by just googling "CD40106 oscillator" - basically, it's a heavily modified version of that simplest resistor-capacitor-inverter osc. The feedback path has been changed from a resistor to a pot in parallel with a transistor, which -kind of- acts as a voltage controlled resistor here (but just for one direction of the charge/discharge cycle). A diode has been added pointing towards the inverter's input - putting a high voltage to it simply forces low voltage on inverter's output, thus the oscillation stops - so hard-gate'ish effect, but complete stop instead of reset. The inverter's output goes to a 1/2 CD4013 which is set as a simple flip-flop frequency divider - it divides the uneven pulse from the inverter by 2 and gives out a nice, pure squarewave. You can see more in-depth explanation of this module in the video below - i was making a show about this system, but sadly it all ended quickly because of the lack of interest from anybody other than me.
