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ADDAC Marble Physics

Eurorack CV Control Module By Paul Nagle
Published November 2016

It’s always fun to discover modules with a different slant on things. The ADDAC503, or Marble Physics, is a CV source that models the behaviour of a marble on a square tray. It generates values for its X and Y coordinates and for the marble’s velocity. In addition, a trigger is produced whenever it hits the edge of the tray. You’re given manual and voltage control over most aspects of the simulation, including the speed, tilt and the bounciness of the edges. To discover why this could be musically interesting, it’s worth starting with some visual impressions of the motion via the Java-based interactive guides on the ADDAC web site. There’s no manual yet, so this is the most direct way to get a feel for what’s going on under the covers.

ADDAC Marble Physics Eurorack CV Control ModuleLuckily, countless Friday afternoons playing pool in my youth have given me a fair idea how spheres on a flat surface behave. It’s only a small mental leap to translate this motion into sound parameters — or movement around a room. If you happen to be involved in sound design for a quadrophonic or 5.1 system, the Marble Physics could be instantly promoted from quirky novelty to invaluable panning tool. Sticking with the motion analogy a moment longer, dynamic stereo sweeps are achievable by temporarily locking the X axis, a feature you can tie to incoming gate signals if you wish. Having locked the motion, Y-plane movements behave rather like a bouncing ball.

The marble starts to move as soon as you tilt in any direction, but there’s a bump trigger button to introduce nudges at any time, their strength determined by an adjacent knob. If you set knobs X and Y in their 12 o’clock positions, the tray is totally flat and no motion is initiated, and when elasticity is at its maximum value, a moving marble will never stop. The only visual feedback throughout is a series of red LEDs in the output section, but these are still pretty informative, showing bounce, velocity and so on. And if you opt for bi-polar modulation, the LEDs offer a cue when the tipping point is reached.

By constantly tweaking the elasticity, speed and X/Y tilts, the resulting motion can be a rapid trip to the nearest corner or an erratic spinning orbit. And rather than have to manually tilt and bump to keep the ball rolling, you can let CV do it instead. There’s a CV input for every function, and as you patch in each one, the relevant knob becomes an attenuator for it.

With a spot of practice the Marble Physics is far easier to use than to explain, and if the effects it generates seem nebulous, they’re also highly dependent on the modules you choose to control. As one of my first patches, I chanced across a motion not unlike a manic bluebottle. I quickly roped in a Mutable Instruments Elements, turning the bounces into strikes, the velocity into Brightness and the X/Y outputs into other timbral modifiers. The bounce action, in particular, can produce an uncannily authentic feel for percussion triggering, and it combines wonderfully with velocity-driven harmonic modulation, perhaps of plucked instruments to offer another example.

I won’t pretend I always guessed what every option would produce prior to patching, but I reckon that’s a good thing. If ever there was a module that rewards experimentation, this is it! Tiny adjustments in either tilt direction often made a huge difference and pretty soon I was gaining fresh insights into modules I thought I knew. Take the 4ms Dual Looping Delay, as another example. It spits out very freaky granular-type material when its clock is driven from, say, the bounce output and you simultaneously modulate each delay time via the X/Y voltages.

As someone who failed A Level physics (but achieved high marks in beer and pool), I’m relieved it isn’t vital to grasp the underlying science to enjoy this module. At its best the Marble Physics gives an impression of being ‘alive’, which places it in a different class from typical cyclic or random sources of modulation. It supplies movement, acceleration and dynamic changes that somehow feel natural, even when they’re defying gravity, flitting around like a mosquito or bouncing eternally for no particular reason. If you’re in need of something genuinely original to perk up your system, the ADDAC503 must be worth a look.