TR-77 Midi with Unipulse

This is how to add velocity sensitive midi to the Roland TR-77 drum machine using Tubbutec Unipulse.

Installation is very strait forward, you just need to solder some wires and drill holes for the Midi socket and learn button. To get a sound over midi, the machine needs to be started and no pattern selected.

Config file here: TR-77 config file
Alternative config file by Jacob Korn (thanks): TR-77 config file alternative version

This manual is just a brief description of how to install the uniPulse, for further information please check out the uniPulse page.

Trigger points

Trigger points are shown for all 13 instruments including Maracas:

trigger inputs 1-7

trigger inputs 1-7

trigger inputs 8-12

trigger inputs 8-12

Maracas CV input (Resistor is 75K)

Maracas CV input (Resistor is 75K)

This is where to get the supply voltage for the uniPulse:

Unipulse supply connections

Unipulse supply connections


It is possible to sync the TR-77 to midi clock, you will however need to start/stop the machine manually.

  1. Start the machine using the ‘button’.
  2. Start the midi clock

In order to add midi sync, you need to connect to the point shown in the picture below. Use one of the uniPulse digital output pins and configure it as ‘midi clock’. You also need to add a 4.7k resistor in series and a switch to select midi clock or internal clock.
The switch is included in the kit, the 4.7k resistor is included on request.

uniPulse D output –> 4.7k resistor —> switch —> point on the TR-77 board

Picture by Burnkit2600

The start stop method also shown in the picture will not work properly. it does not switch the machine between started and stopped state, but rather toggles between them on each start. That is somewhat usable but not perfect.

Installed board

And this is how the installed uniPulse board looks like (These pictures show the old MK1 version)

unipulsemount socket

Here is a very nice install picture by Ramcur Vintage Electronic Repairs showing a MK3 uniPulse installed in a TR-77