Resonant Frequency: Boss DR-110

Trigger Outputs

My main goal with the DR-110 was to be able to interface it with the outside world. In a prevous article, I described how to add a 12ppqn sync input; allowing the DR-110 to play in time with external sequencers. Now I've discovered a simple way to add trigger outputs for each voice of the DR-110.

The stock DR-110 already has an "Accent Trigger Output" circuit on board. It converts the negative-going CPU pulses to 6V, 10mS positive-going pulses. You can see this portion of the circuit on the section of the CPU board shown. (I have full DR-110 schematics available for download). As the CPU accent pulse goes negative, it allows capacitor C4 to discharge through D9. This in turn causes Q1 to conduct, pulling the accent output (through R5) to the positive rail (which is 6V in the DR-110)

I felt the stock accent trigger circuit was simple and effective, so I decided to replicate it for each of the drum voices. I simply copied the circuit components listed here:

D9

C4

R3, R4, R5, R6

Q1

Looking at the ribbon cable connections at the edge of the CPU board schematic, you'll see the following CPU pulses:

CH - wire 11

OH - wire 10

SD - wire 13

BD - wire 12

AC - wire 16

CY - wire 9

CPI - wire 15

CPII - wire 14

There's a total of 8 CPU triggers that go to the voice board. One line is dedicated to Accent (which already has a trigger converter). Each other drum voice has it's own independent trigger, except the handclap which has 2 (one for a single clap, and a triple trigger for the slightly delayed hits around it). All you need to do is clone the accent trigger circuit 7 times and put it on a small perf board. I connected the trigger output board to the DR-110 CPU board with an 8 pin ribbon cable, and carefuly soldered each wire to the appropriate ribbon cable connections. Remember that the accent circuit is already on board. The positive accent pulse is available on the ribbon cable at wire 18. I also added a 2 conductor wire to supply power and ground.

I chose to strap an LED across the trigger outs, so I have a visual indication of which drum voices are firing at any given time. I duplicated R5, so that the collector of Q1 was tied to 2 1K resistors. One feeds the trigger output, the other feeds the LED. I connected all of the trigger outputs to a 9 pin D-sub connector which provides the 8 trigger outputs and a ground connection. For a unique look, I used a numeric display LED instead of 8 individual T-1 (3mm) LEDs. It's pretty wild to watch the numeric display, because it creates a bunch of weird alien characters on Playback.

Of course with this new circuit board, LEDs and D-Sub connector, you'll run out of space inside the DR-110 case. You'll need to come up with a crafty method to attach a new box. I simply added a small box off the rear of the case (above the grid display). I used super glue and a few #4-40 screws, nuts and washers to make a strong, permanent connection. I hope to add pictures soon.

The Resonant Frequency website is designed and maintained by

Dave Magnuson