El Kabong

This thing is more fun than a barrel of monkey-barrels. The big idea is a sensor on a very sproingy strip of metal (at right above). (see block diagram below) that sends a model of the metal-strip’s motion to a gallimaufry of processors including:

a simple output,

a specially designed wave -multiplier circuit, This circuit multiplies the frequency undulations of the blade and the multiplication factor is indexed to the amplitude of the undulations.

a mixer connected to the source input of sample & hold circuit

and a comparator with a variable threshold

The wave multiplier circuit feeds a second comparator which provides the sampling triggers for the sample & hold circuit.

…And the whole glorious mess is tapped at several places throughout for it’s seven CV, gate, or trigger-pulse outputs, deployed as both 1/8″ jacks and banana jacks on the rear panel.

The comparators bear a little extra explanation. A comparator is a very simple device. It has 2 inputs and one output. it flips the output voltage ‘on’ or ‘off’ based on whether the voltage on one of its inputs is higher or lower than the voltage on the other input. It’s a simple concept but when one of inputs is a very complex wiggling voltage and the other input is set very carefully at a strategic ‘tickle-point’, the resulting patterns can be very rich. This is why I used knobs that were marked with very fine gradations. It allows me to make very fine adjustments to those thresholds.

Another design feature is that I implemented 2 comparators, one wired to the unprocessed wiggles of the blade. The other sensing the multiplied wiggles of the processed blade.

This is a happy machine! As an experience, building these instruments really covers a wide emotional range for me. Some of the projects are interminable grim marches, fraught with heartbreaking setbacks… but ending in a rich payoff at the end of the schlogg. Others are just interminable grim marches fraught with heartbreaking setbacks….

And a rare, happy few are just an unalloyed hoot from start to finish! El Kabong was one of those. The ‘hardest’ part was the search for the object that would provide the original physical motion. I was busily mining my prodigious landfill of the detritus of bygone technological generations* looking for an object with optimum sproinginess. In a few cases, I found myself using a hacksaw to ‘liberate’ these experimental subjects from their original moorings. But nothing really ‘sang’ to me. But then, while I was merrily sawing away at an old Crown phono-preamp chassis I felt a thrumming vibration in my hand and realized that my hacksaw blade was oscillating as I was drawing-back for a cut. Eureka! The hardware store has piles of hacksaw blades, but I knew FOR SURE that THIS ONE could sing so I removed it from the saw frame and Voila! A star was born!

The only real modification the blade required was dulling the teeth a bit because I was getting a bit chewed-up when manipulating it incautiously.

Playing this controller is a hoot. You just bend and twang the blade and all manner of complexity emerges from the outputs . All this merriment is not without some price. The wave multiplier must be carefully centered in order to yield all the harmonics & sidebands that can be squeezed from the blade’s motion and this centering will drift as the physical temperature of the blade changes. So it requires frequent ‘tuning’. This doesn’t bother me though. It’s no more obtrusive that some temperamental guitars that I’ve put up with over the years.

In practice I discovered a very rewarding technique,

Figure A (below) shows the normal motion of the blade when I twang it. But I discovered that I can significantly increase the range of blade motion by clipping a screwdriver with a large heavy handle to the top of the blade and by sliding the screwdriver up or down (Figure B) I extend the mass of the blade and I can vary its rate of swing a great deal (Figure C)

and … I also discovered that if I lightly steady the top of the screwdriver and twang the middle of the blade, (Figure D) The blade ‘shimmies’ in a fast. two-node oscillation , not unlike a guitar string .

These tricks greatly expand the range of the instrument. And they make it even more fun to play with.

An example of the screwdriver trick can be seen at roughly 1m.16s on this Hearding Cats Collective performance video.

Oh… and as for the name? As a kid, my Saturday mornings belonged to Hanna-Barbera. I offer this as explanation.

*a source of terror that no doubt haunts the nightmares of Mrs. Mabuse, my saintly, patient, beloved and avidly tidy spouse.