Roland TR-808 Clone

I was curious about how those smart Japanese engineers at Roland made the TR-808 sound so cool. I found the schematics online and decided to build some of the drum oscillators as individual modules. So far I’ve cloned the kick, snare, and hi-hats as faithfully as possible to these original schematics, except I substituted currently available semiconductors whenever obsolete ones were called for; BC546 and BC556 transistors seem to work fine. As a power supply, I found that the tiny muRata NDTD0515C DC-DC converter works nicely, boosting juice from a cheap wallwart up to +/- 15VDC bipolar power.

I havent yet deciphered how Roland crammed all of that VCA-envelope generator functionality into just a few transistors, but… someday it will make sense.

Currently, my 808 clones have made a nice home in the Big Box o’ Techno. There is plenty of circuit-bending opportunity now that the drums are assembled and laid out side-by-side with no enclosure to get in the way.

If you are interested (and crazy!) you can download my Eagle project files containing schematics and perfboard layouts for the kick, snare, hats, and cowbell… I haven’t yet built the cowbell but the layout is complete: TR808 Eagle Project files . The layouts are designed to fit onto PC-4 prototyping board from All Electronics.

From front to back - 808 hihats, snare, and kick

Trigger and Accent inputs - Each drum has a TRIGGER and ACCENT input. In the 808, the accent input is a global signal that boosts the level of all drums when requested (TTBOMK). In my clone, I just have a potentiometer set up as a voltage divider to deliver a constant voltage to the ACC input. It is basically a volume control in this arrangement. The trigger inputs are a little more tricky; if you are driving the drums with a logic circuit, you’ll need a little bit of trigger generator “glue” inbetween. Basically this lets the energy of the positive transition thru to trigger the drums, and shaves off the negative edge. If you omit the trigger generator, the drums sound weird b/c they will also trigger on the negative edge, with a different and weaker tone, reduced decay time… basically it sucks.

Trigger generator network