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 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!

How to open unsigned app on OSX

This is how to open our Firmware updater utility on OSX. This should work with any other unsigned app as well. This has been tested with OSX Big Sur but probably works with older OSX versions as well.

Step 1:

Download the app. Safari will place it in the Dowload folder. Navigate to the Download folder in Finder.

Right click on the file and select “new Terminal at Folder”

Step 2:

A terminal window opens. Type the following command: (you can copy and paste it here)

sudo chmod -R 755 ./

You will be promted for your password. Enter your password – it will not be visible. After entering your password press enter.

Step 3:

Open the folder with the little arrow on the left, right click on the “Tubbutec Firmware Updater” application and select “Open”

You will see a message that the file can not be opened. Click Cancel.

Step 4:

Repeat step 3! The second time you click open, the following window will appear.

Click Open and the app will start 🙂


Boss DR-55 midi and more

One of our customers, Landon Balk, used the uniPulse midi interface to add midi to his Boss DR-55.
He also completely modded his machine and constructed a custom case.
You can purchase the case directly from him: facebook site or website.
This manual shows how to install uniPulse in the Boss DR-55 based on his instructions.
Please read carefully before purchasing the uniPulse mod. If you want this to be done by a tech, get a quote first!

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Colundi on the µTune

Colundi µTune logo

Introduction to Colundi

Some users of our µTune eurorack quantizer and midi interface have asked if about the Colundi scale and how to use it with µTune.

Here is a quick tutorial how to set it up.

The Colundi Scale is somewhat different from traditional scales in that it consists of absolute pitches, rather than relative intervals.

There are different Colundi scales, in this tutorial we will use the list published here:

The scl. file we created using these frequencies can be found here:
Colundi scl file

Update: Here is the scl-file for the complete final list with 128 frequencies:

At the end of this tutorial, we will show how to create such a scale file yourself.

Using a Colundi scale file with µTune

Using the Colundi scale file is pretty simple with µTune. This explanation might look complicated, but it is only very detailed.

  1. Put the scl file on the SD card an load it in µTune
    (Alternatively you could use µTune’s scale editor and enter the scale manually)
  2. We need to define a reference frequency used by µTune’s tuner:
    As a reference you could use the lowest note (10.8Hz), but probably more practical is to use a note in the audible range. Looking at the list of frequencies again, we notice that note number 30 is supposed to be 440Hz. Great.
    Go into TUN->Scale Mapping and define out reference note to be 29 (The base note is note 0) and the reference frequency to be 440Hz. (Note: You can use any other note and frequency as a reference)
  3. µTune is now able to calculate all absolute frequencies of your scale.
  4. Connect the output of your VCO to µTune’s GATE-in input. This can be used to measure the VCO’s frequency.
  5. In µTune’s tuner, you can use different display modes. You could display the frequency in Hz and check the frequencies of the different notes. Better is to use ‘relative mode’ to display the difference between the expected and measured frequency from the VCO.
  6. Adjust the Tune knob on your VCO until it is in tune. You might have to adjust The ‘Middle volt’ and ‘middle note’ settings to get the VCO in range. Please refer to the µTune user manual chapter ‘Scale Mapping’ for a detailed explanation.
  7. You can now play your Colundi scale and have fun!
  8. Optionally: You can now also use the ‘automatic tuning’ feature to make sure your VCO stays in tune automatically at all times

Creeating a Colundi scale file yourself

As you can see, the first frequency is 10.8Hz, followed by 33Hz, 33.8Hz, 55Hz,…

We now have to convert these frequencies into ratios based on the base frequency and calculate the difference in cents.
By the time of writing this, in Scala you can enter the frequencies directly, Scale workshop does currently not support this however. A simple Excel script can do the job for you as well.

Our base frequency fbase = 10.8Hz which we define to be 0 Cent.

The cent distance from our base frequency can be calculated as:

cent = 1200 × log2 (fn / fbase)

The cent value of out next frequency f1 = 33Hz can therefore be calculated as:

cent1 = 1200 x log2 (33Hz / 10.8Hz) = 1933.72165 Cent

The next entry in our scale is:

cent1 = 1200 x log2 (33.8Hz / 10.8Hz) = 1975.19032 Cent

and so on.

When you are done you can use your list to create an .scl file. You can do so using Scala, Scale Workshop, µTune’s scale editor or a simple text editor. The .scl file format is very simple and described here.