Yet another issue, yet another module. I have a beatstep pro as my main sequencer. I love it, it’s great, but some things about it are just a pain in the ass. Unless you’re recording in realtime setting note lengths is a drag. Want some long sustained notes, you’re in for a lot of knob turning. So, after enjoying a reasonable amount of frustration, I designed a module that will take any gate input and lets you lengthen ( or shorten ) the gate duration. [ I recently found out the key step does indeed has an easy way to lengthen notes so making this whole endeavour pretty ¯\_(ツ)_/¯ , but anyways… ]

Circuit design

The circuit is a rather simple one. It consists of 2 parts. First, the incoming gate/trigger gets sanitised. For this, a simple, passive high pass filter, fed into a comparator is about all it takes. As a result, you get a well defined pulse of determined length. That pulse gets used to charge a capacitor. When the pulse goes down again, the capacitor will drain through a variable resistor (aka a potentiometer), when the resistance is low, the capacitor will drain to GND quickly, when it’s high it will take longer. This will give us a decaying voltage over time. Now, up to the second comparator which will make the signal ‘high’ when the voltage of the decaying capacitor is positive and low when it drops below a certain threshold ( somewhere just above GND ). All that’s left to do is to add a diode to keep the signal from going into the negative as we cannot know for sure if the receiving module would allow for a negative voltage at its gate input (It should, but better be safe then sorry). Since we’re sanitising the output signal, it won’t hurt to scale it down a bit as well so it isn’t putting out 12V gates, but stays more along the 5 to 6V range. There is no real standard for gate signal levels as far as I know, everything above 3V should be fine but as a designer you don’t know where people will put it ( please, don’t send me pics ). I’m more at ease around 5 to 6V as that seems to be more or less the norm. Not too hot, not too weak.

Schematics

click for pdf

Some DIY info

The only thing of any importance really is the gate length, which is determined by the value of R15 and RV1 ( only focussing on ch 1 at the moment, ch2 is just a copy ). R15 determines the minimum length, and, as drawn, will result in 2ms which is about the length of your typical trigger pulse in Eurorack land. I have used 100kΩ pots for RV1 which results in a maximum time of around 2 seconds for the gate time. I found that an adequate length, but you can change the pot value to something like 1MΩ if you want to be able to generate longer gate lengths.

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