[sdiy] Negative-going triggers in the Boss DR-110 drum machine - Why?

Benjamin Tremblay btremblay at me.com
Fri Sep 29 13:45:59 CEST 2023


Surely it’s all about minimizing parts count. If your microprocessor can just as easily generate an inverted pulse as a non inverted pulse, it can save a few pieces of silicon.

This seems consistent with the old lines of drum machines. 
Example, my TR-66 uses low-going pulses.
Example, my Korg Mini Pops machines have their decay capacitor tied to +V and decay is the charging of the cap, not the discharge.

The simple “swing-vca” envelope circuits often needed to be pulled to ground or -V. 

The ringing filter circuits (twin-t or coil) normally use a positive-going pulse, and the DR-110 does for the kick drum too.
(But noting the snare oscillator triggers with a negative pulse here.)
And as you might expect, a ringing circuit does not care so much what phase the trigger pulse is in, as long as it sounds nice with the other drums.


I just stuffed a DR-110 analog board into my Drumbrute.  After trying some logic chips, I settled on some cheap transistors to invert the logic for the snare, clap, and cymbal sounds. 

A Modwiggler schematic shows a diode added to the bass drum trigger path. I did not see any benefit to this with a drum machine that guarantees a well-formed pulse signal.

Benjamin
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