Circuit Bending a Boss DR-55

My father in law gave me an old classic Boss DR-55 analogue drum machine a while back, but it doesn’t have any trigger inputs, or MIDI control, or clockability. You can’t tweak the individual drum sounds either really. So… I decided to bend it a bit to make it more usable.

I started this a few months ago, but kinda messed it up out of inexperience, so put it away in a box in a cupboard and finally fixed it up over the past few days.

Specifically I put in bass drum mods - pitch and decay, though they both intermingle a fair bit. I also put in trigger points for the three main sounds. Anyway, have a watch if that’s the kinda thing that you are interested in. If you have one and need help I can give you my very basic knowledge ha.


Very cool. Despite its rubbish kick sound, I’m quite fond of the DR-55 and just spent a couple of days laboriously sampling and programming a track with one. It would have been much more fun to do it this way!


Hey! I‘m just in the process of modding my DR 55 and can’t find good info on the trigger in mods. Would you care to share your knowledge? :slight_smile:

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Hey there,

I used the following guides:

The trigger mod input is really easy. You basically look for the three wires for the kick etc which are clearly marked, and then inject a single into them. The hi hat was trickier so I gave up :slight_smile:

Best of luck!!


Thanks! Singles as in single 1/8“ jack sockets? And just connect the positive to the respective wire and the ground to… ground?
I found these pages as well, but the only one suggesting individual trigger inputs was a bit vague. Much appreciated!

Sorry, auto-correct fail. Signal, not single :slight_smile: You can use whatever jacks. I used 1/8" jack sockets in and wired them up as you described. Positive to the wire. I just soldered them right on. Then ground them to… err somewhere on the board that I can’t remember :smiley:

I can’t find the page where I found the trigger info… or maybe I made it up. Anyway, the wires are detailed on the schematic and easy to find, but I think they are the ones in the lower left of the below picture - the three that run horizontally


Ah! Now that i can work with :slight_smile:
It‘s described on the ‘machines.hyperreal’ page. But it sounds more like a hypothetical experiment with unknown consequences on there… thanks a bunch! Will try :crossed_fingers:

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Somewhat unrelated, but it’s heartening to see that Hyperreal is still online after nearly three decades.