Compact Clock Source, or the CCS, is a small but really versatile module. At its core, it is a dual squarewave VCO. It draws roots from the same place your favorite drone machine most likely does - the cd40106 hex inverter chip. But the CCS has a bunch of aces in its sleeve!
It is based on my own custom circuit which allows for a nice decent frequency range and a more or less feasible CV response. I first made this circuit for 'sound' VCOs in my lunetta box, but they obviously work just as well as clock generators. Thanks to the output of the 40106 being divided by 2 via the 4013 flip-flop, the output is a nice 50/50 duty cycle squarewave. You can find a photo of the original schematic drawn on paper in the Pictures section.
Other cool feature of it is that it has both a normal and an inverted output for each clock (trust me, this is very useful!) and a XOR of the two clocks as a fifth output. Outputs are cross-normalized to the CV inputs, so the module is ready for cross-modulation of the clocks for more rhythm fun. Such a module allows for interesting patterns to emerge moments after you touch it at all!
UPD 1 APR 2022: 2 years passed since this design was made, and i finally replaced it with a much better one. The new design is not way harder to pull off than this one, but is very obviously more usable and has better clock frequency range and voltage control response. You can still build this one, if you feel like it, but i strongly recommend to check out the new design.
Schematic
This one is fairly simple. You take your obvious fixed 40106 oscillator and make the feedback resistor real big, then just put a transistor across of it. It will act as a voltage controlled resistance for one half of the duty cycle (and ignore the other). The base to emitter diode improves frequency vs CV response. This way we get voltage control over the pulsewidth AND the pitch at the same time, and they cannot be separated. To compensate that, the output is processed through a 4013 in flip-flop /2 divider mode and get a nice even squarewave at its output. As simple as that!
The output is then taken to an inverting output jack, then inverted via a 4030 XOR gate in inverter mode (one input tied to +V) and output to a normal output jack and an LED. Why not vice versa? I wanted the XOR output to be a function of normal outputs, not the inverted ones, so it's just a matter of labeling! The same output is also XORed with the normal output of the other clock generator, and also normalized into other half's CV input. Very simple, but lots of fun!
Media
Just a little demo: the the XOR out is a trigger for Bastl Instruments' Tea Kick, the inverted CLK A out is a cv for its pitch. The only thing i do through the demo is adjust the settings of the CCS. Just look at how many different rhythms i got out of it!
A slightly more advanced four voice drum patch which makes use of the entire CCS. Paching XOR output into the A CV in results in very itneresting pseudo-sync effect. Again, i am only touching the frequency and cv amount knobs of the module through the recording. To me myself it is fascinating how much the pattern changes just from a little tickle on the CV amount knob.
