Hohner Rhythm 80 Midi with uniPulse

This manual describes how to use and install the uniPulse midi interface in a Hohner Rhythm 80 drum machine.

Installation requires soldering some wires and drilling holes for the midi socket. However no need to cut any traces.

midi socket installed in a rhthm 80

Picture by Beatkamp

After installation you will be able to trigger all sounds via midi, most velocity sensitive.

Bass Drum
Low Conga
Low Bongo
High Bongo
Cow Bell


Unplug the Rhythm 80 when working on it!
After opening up the enclosure, you are presented with the following view of the boards:

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Hohner Automatic Rhythm Player Midi

This manual describes how to install our uniPulse midi retrofit in a Hohner Automatic Rhythm Player.
After installation you will be able to trigger all 10 sounds, most of them fully velocity sensitive. You will not be able to sync the internal rhythms to midi clock however.

Soldering pulse triggers

Installation is fairly simply and requires you to solder 10 wires from uniPulse to points on the Rhythm Player voice board. These are P1-10 and CV (as labelled on the back of the uniPulse board). The black P7 wire is not used.

Unplug the machine, remove the slotted screws and open it. Then solder the wires as shown in the following pictures. The “CV” connection used for the Maracas needs an additional diode. Any Diode is fine here. As you can see, the cathode of the diode (marking) connects to the cathode of the existing diode.

Installing uniPulse GND and VCC

The supply voltage connetions for uniPulse are GND and VCC. Note that the GND wire is red and the VCC wire is brown, unlike normal conventions.
The following pictures show the locations to solder the VCC and GND wires:

INstalling the midi socket

In order to install the midi socket you need to drill 3 holes. A stencil for drilling is provided. For the large hole you can use a stepping drill. Now mount the socket using the screws provided.

Mounting the unipulse board

You can mount the uniPulse board anywhere in the machine. We decided to use thick double sided tape to mount it on the rear. Make sure the board can not short to the metal chassis.

first start

After installation, plug in the machine and turn it on. The LED on the uniPulse board should light up indicating proper power connection. Using the uniPulse configurator tool, upload config file for the Hohner Rhythm Player (zipped, extract before opening in the configurator)

That’s it! have fun!

CR-78 midi with uniPulse


  • Midi trigger of all CR-78 instruments, most fully velocity sensitive. Guiro pitch can be controlled slightly.
  • Midi controlled accent trigger (send max velocity 127 to trigger accent). Accent amount is still controllable via knob.
  • Instrument mixer on CR-78 will continue to work.
  • Sync via midi clock, switch between internal clock and midi clock via toggle switch.
  • Use CR-78 Rhythms and midi control simultaneously.
  • Not need to cut any traces, installation is completely reversible.

Get the kit in our shop (select Version: CR78)

Installation manual

The installation manual as PDF

Config file

Config file Download (Right click, save as)

TR606 UniPulse Installation

Buy uniPulse in our shop!

uniPulse TR-606 features

  • Full velocity control of all 7 voices
  • Six (6!) additional sounds (An 808ish deep clicky bassdrum and a higher pitched one, Only Snare Noise, Only Tom Noise, Each half of Cymbal (the hitting sound and the decaying sound))
  • Midi clock input. Clock is also sent to external din-sync devices.
  • Midi controlled Open hihat decay
  • You can install an additional midi socket, or use the existing DIN-Sync socket

After installation you can trigger the following instruments on midi channel 10:
BD: 36
SN: 38
LT: 45
HT: 48
CY: 49
OH: 46
CH: 42

and the extra sounds:
Bassdrum 2: 37
Deep Kick: 35
Felt Cymbal: 52
Snoyze: 40
Brush: 47
Closed Cymbal: 51

Open hihat decay CC: 19 (when counting from 1), 18 (when counting from 0)

The midi channel and the notes can be modified using our configurator tool (see below).

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Hammond AutoVari 64 midi with uniPulse

Thanks to Jonas Olesen we now have a comprehensive uniPulse installation manual.
He also installed extra outputs and pitch mods which are of course optional, but recommended modifications.

Note from Tubbutec forum user Cyrano1 :
Note this is only for AV-64 MK-1 boards (->1979).
Auto-Vari 64 MK-2 board (1980) has completely redesigned unit on one single board with various ICs that is totally different.

The Hammond Auto vari 64 – Unipulse installation and modifications

By Jonas Olesen

some more info in this thread.


The power wire in the back goes directly to exposed solder joints besides the transformer, BEFORE they go
into the transformer. This means that 220v is completely exposed – be careful.
I glued a piece of plastic on top of these joints.
The service manual is extremely well written and explains almost all circuits in detail, and combined with
the fact that all connections in the machine are marked with their functions in plain English, makes the
machine very easy to work with.

Installation of the Unipulse:

Very straightforward – simply cut the wires in the voiceboard connector and solder on the unipulse triggers and power. Then reinsert the connector.
[Tubbutec: We believe there is a way to avoid cutting wires, but lacking a machine we can not test this. If you own a machine and want to test this, please get in touch]

I attached the unipulse board to a piece of wood glued and screwed to the chassis.
Trig outputs 1-9 triggers the sounds, except brush and sandblock.

On the front of the Autovari I have installed 10 additional outputs from the Unipulse, so these can be used
to trigger / synch other machines. Please note that the back panel is too thick to attach minijack outputs,
The fron panel is thin metal, and there is a lot of space for outputs and additional potmeters here.
Midi input installed on the back besides audio outputs.

Small corrections to the Tubbutech voice board trigger points:

Bassdrum trigger: differs from the drawing, has to be Bassdrum besides it (has a wire)
Brush has no wire in the connector, it will probably trigger if the trace is followed underneath the voice
board, but I did not implement it. Strangely the Brush plays in the internal rhytems, although no visible wire
is connected to it via the voiceboard main connector.


Low frequency output:

Seperate output for the low frequency content.
Main output contains both hugh and low content – the balance pot located on the back is moved to the
front – from here the balance can be set to only high frequency content.
This way there are a seperate output for low and hugh content.

Pitch mods:

Easy and a must do!
I found the resistors by poking with alligator clips – the online scanned service manual is so low resolution,that the resistor numbers can not be read.
1: Bassdrum: Replace R4 with a 50k log pot
2: Snare drum low frequency: Replace R65 and R55 with a stereo 50k log pot
3: Conga: Replace R14 with a 50k log pot
4: Bongo. Replace R23 with a 50k log pot
5: Claves: R33 + R32 50k log Stereo pot (to obtain a wider pitch range)
6: Rimshot: Replace R40 with a 50k log pot
Cowbell: The cowbell consists of two seperate sounds:
7: Cowbell 1: Replace R50 with a 50k log pot.
8: Cowbell 2: Replace R58 with a 50k log pot.

Not implemented:

Sandblock CV trigger.
Brush trigger.
Decay mods.
Sync clock:
Not tested

Download the config file (you need to extract the pconf file from the zip file).

Rhythm Ace FR6 uniPulse install

This manual describes how to add velocity sensitive midi to the Rhythm Ace FR6 using uniPulse.

Picture via Matrixsynth

This was not tested by us, but a friendly customer provided pictures and a schematic drawing for the sync circuit after a successful installation. Thaks to Pieter Vochten.

Configuration file is here. (Right click, save-as)


The picture below shows the trigger point locations. Just solder uniPulse wires P1 – P8 to these points.

Board overview, Unipulse triggers soldered in place:

Board placement:

Connections on backside:

uniPulse power

Solder unipulse wire V+ to the V+ point shown in the picture below. Solder uniPulse GND to the V- point.

Clock and sync

Schematic diagramm, showing the clock and start/stop connections:

Clock connections, resistors not shown:

Transistor placement:

Start/stop connections in place: