Most who are familiar with the circuit design work of Peter Blasser know about the Rollz. It first appeared as the ROLLZ-5 Drum Machine. The Rollz-5 PC board, designed by Meng Qi incorporates four of the Rollz circuits, which can be built with anywhere from two to six stages. The Rollz became an important section of Plumbutter and Peter even created the Rollzer to use with the Plumbutter. (Rolls with butter.) Rollz acquired voltage control over its rate in Plumbutter. Peter published the entire Plumbutter schematic.

Not long ago I was gifted a nice collection of PC boards, designed by Josh Rodriquez. One of them was a 5-6 Roolz board. The circuit is derived from the Plumbutter design, extended from the 3-4 Rollz. Josh also sent along the nice panel (above). How could I resist building it!

Construction

Operation

Peter offered this circuit description in his schematic document.

This capricious circuit theory started in the Enoch Pratt Free Library, in Baltimore, inside a dusty book by Delton T. Horn, named simply, “Oscillators”. In it, he details many laboratory oscillators, including the worthy two transistor multi-vibrator. Delton did detour in a short paragraph about a “3 transistor multi-vibrator [that] produces exotic tones”. He explained that its behaviour is not quite predictable and changes wildly based upon the current injected at each base. Wild changes (current controlled!) are the hallmark of a chaos vortex, and this one is stimulated by a simple paradox: three is an odd number.

Let me explain. Each stage on a multi-vibrator is an inverter. So, with an even numbered multi-vibrator, starting at a stage that is ON, the next node is OFF, and if it is two stages, back to the first one, which is ON again. It is self-reinforcing. However, thinking about a three stage multi-vibrator, ON, OFF,ON; the start is now OFF when it was ON! This oscillator contains a paradox, so it spirals out of control, into ultrasound frequencies with much noise. If you connect it with the nodes of an even one, well, you get a combo of rhythm and noise, thus a drum-machine is bourne.

Peter also wrote the following in the Plumbutter manual.

Brown bananas are androgynous pulse nodes. Orange bananas are strict outputs. Blue bananas are strict control inputs, which are labeled with a V for Verso, and an I for Inverso. V means that a positive-going input causes the oscillator to speed up, and I is vice-versa.

Each Roll has a knob to control its rate. The brown jacks, it must be emphasized, are androgynous in that they are both inputs and outputs, which means that a pulse output can be connected here as well as a pulse input. Connecting two brown bananas to each other merges the rhythm of their rolls. The reason there is one orange output per roll, is to provide some information about its state in control voltage format, to modulate other things. Here it should be said that brown bananas deal in negative pulse spikes which are not compatible with control voltage circuitry.

The brown jacks are infamous in Ciat-Lonbarde lore. They are meant to be patched only to other brown jacks. Since they are directly connected to transistor bases, they should not be patched elsewhere. The orange jacks are for patching to other parts of a Ciat-Lonbarde system (or other system). To clarify it can be useful to look at the Rollz outputs on a ‘scope.

Rollz is powered with a single 9-volt supply. See how the upper trace (yellow) cycles between zero volts and plus 9 volts. The scope even tells us the p-p voltage is 9, the minimum is 0 and the maximum is 9.

Now consider the blue trace, which is a Brown jack adjacent to the Orange one we’re looking at above. Maximum is 1.20V, minimum is -9.40V. Woah! Some folks are surprised to see a large negative voltage coming out here, when the power supply is going between 0 and +9V. The reason is that we’re seeing a capacitor being discharged quickly, the negative spike followed by an almost linear rise back to +1.20V. I hope that helps us understand what’s going on with the Brown jacks.