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Klavis Logica Gater

Eurorack Module By Paul Nagle
Published August 2017

Another seriously compact offering from Belgium, Logica Gater, is a combined logic and gate module. Logic decisions may not sound particularly sexy, but their on/off decisions cover simple duties such as clock division and are especially valuable for plucking order out of chaos, or building complex, rule-based patches.

Size: 5HP. Current: +12V = 0mA, 12V = 1mA, +5V = 16mA.Size: 5HP. Current: +12V = 0mA, 12V = 1mA, +5V = 16mA.Logica Gater evaluates the state of up to three input signals plus a manual button and produces both regular and inverted results. All operations work in the same way, beginning with ‘And’. In this case the main logic output will be on when all inputs are also on (ie. non-zero). Switch the mode to ‘Or’ and the decision merely requires one of the inputs to be on.

‘Xor’ is interesting because it has an extra function you don’t immediately spot. Ordinarily, it sets the main output to off when all inputs are on. But it can also function as a digital ring modulator similar to that of the ARP Odyssey and Korg MS20. Feed a pair of oscillators into two inputs and you’ll soon appreciate the bonus. It transpires that this logic processor has other useful audio properties too. For example, its Flip Flop output (which changes state whenever the main output changes) can function as both a sub-oscillator creator and clock divider.

The other logic processes work as their names suggest, optionally producing the ‘on’ output depending on the state of just a single input, or when an even (or odd) number of inputs are on. You’ll be glad to know it’s easier to use than to write down! The last function is rather fun — ‘Gater’. It works like ‘Or’ except that the gate lengths of incoming signals are preserved and it retriggers the output for every new gate that’s received. So it can be an interesting way of mixing multiple sources, sequencers, keyboards, Sample & Hold modules, etc. into a single rhythmic mulch.

Unlike typical logic modules, you’re able to change the logic operation via CV input, so you aren’t confined to the same decision repeated over and over. Perhaps one final example is worth including, since unless you’re Mr Spock, talk about on and off states can be rather abstract. I tend to use logic to gather multiple events that occur, either randomly or in patterns, and for this, ‘And’ does the job. Suppose you are running three sequences of irregular lengths, each looping independently. Further suppose that each sequence has a single note in the first step and that you wish to trigger an extra event when all three overlap (a sample or chord maybe). ‘And’, fed by the gate outputs of the three patterns gives you this capability. A darn useful little module.