EuroRack Sequencer

I must admit that this all synth stuff is a bit pointeless without the proper actual case in place. On the other hand, once I got one I’ll be able to populate it with my stuff. It isn’t really my fault, why is electronic design so interesting ? when you design such musical stuff, it’s the perfect blend between engineering and Art, isn’t it ?

Anyway, this won’t be the new wheel but will complete the previous envelope generator and drum synth. I wanted something flexible and powerful in a small HP format because those modules are very hungry-space.

Therefore for this project I limited myself to 8 steps going up or down and with all the parameters gateable (is that a proper word ?). Meaning that all push buttons can be substitued with a gate applied to the coresponding input. I think this will prove itself very handy in a modular system. (a 16 steps version in a stand alone format is another idea)

So nothing really magical, a binary counter (CD4029) with an UP/DOWN ability, a multiplexer (CD4052) few fliplops (CD4013) for the switching and load of switch and jacks. I want to use momentary button rather than the crappy blue one.  they’re more nice to use and you don’t run the risk of breaking them as easily as you do with the crappy blue one.

Here’s the prototype’s schematic. I’ve no plans to build the all project on breaboard, it will be a massive PITA! I’m just breadboarding things I’ve doubts about. Making sure they work good before going into the solder!sequencer_eurorack_jpgI won’t go into the working details of the chips (datasheet will explain all of that) but here are few details and the overall fonctioning of that stuff.

CD4013 flipflops are used as switch, actived by the push button (or gate) to control the counter.

The start/stop option needed a bit of thoughts. The counter can be stopped by putting the carry in pin High. Easy enough. But the issue was that I wanted to stop the clock, not the counter, in order to use the “step” button to increment manually the counter. So I actually needed to stop the clock, or at least cut the connection between the counter and the clock.

In the preset schematic, the method is to use a transistor as a switch. The clock signal must be high enough to go above the threshold of the counter therefore the poor transistor isn’t powerful enough to completely cut the path, the clock is still a the output but reduced enough to not distrub the circuitry and let the “step” button do its role.

The reset is produced by a pulse at the coresponding counter’s input. 4 sources can cause in reset : A gate, a manual gate, a limited set of steps (rotoswitch), or the normal reset of the counter (8bits).

Two CD4051 are used. One for the CV output (normal and glide), the other for the logic level (gate, resetcount, LED, ect…). To maximise this project, each gate may be available (creating if needed a Gate sequencer).

One could argue that a digital solution instead of all those ICs could be more efficient. But all those ICs are fun and idiotproof. And when the world would be ruled by Apple-Google-Skynet I’ll be happy to have played with those “analog” chip in my youth.

Now I need to get out more, try to have a life and stop writing stuff that only geeky geeks care about (or not)…

thanks for reading !


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