UniMatrix Oberheim TVS Installation Guide

Introduction

Note: Most TVS units include a digital keyboard, also known as a diode matrix keyboard, with which this modification is compatible. Some early TVS units have an analog keyboard, similar to an ARP 2600, which can be identified by a transposition rotary switch instead of a transposition slide switch. If your unit has the earlier analog keyboard, this kit will not work.

This installation guide assumes you are familiar with electronics at an intermediate level or higher. It also assumes you do not need instructions on how to open the unit and access the underside of the left-hand controller where the PCB is located.

Here is a photograph of the finished installation. Note that another diode matrix product was installed previously, and the solder work in this photo is not aesthetically perfect.

Mounting

The mounting holes on the UniMatrix are not large enough for standard American hardware.

However, a 6/32 screw will fit with some encouragement. We removed one nut and replaced it with a 1/4" standoff. We then affixed the UniMatrix to this standoff using a nylon spacer between the PCB and the standoff. You may consider using a 6/32 - M3 converting standoff.

Power

+10V and ground can be sourced from most CMOS ICs on pin 14 and pin 7, respectively. Use a multimeter to confirm these voltage levels. The power wire included in our kit came with three wires; the third was unused and has been cut off.

Midi In

We mounted the MIDI jack on the rear I/O plate and ran wires to the UniMatrix. Since we did not want to splice wires, we soldered the wires directly to the available pads on the bottom of the UniMatrix PCB for MIDI input.

Wiring In Data Signals

All necessary signals are available on the large molex header that connects the keyboard to the logic PCB.

NOTE: The header is a 15-pin header with 2 keying positions. The 9th pin has a physical plug for keying and is counted in the pin count. This is especially important for the stimulus pins. The 2nd keying position is pin 15, which is unused.

I/O 1-8 Connections

Stimulus Pins (I/O 9-16) Connections

For the "Stimulus Pins", I/O 9-16 header, you only need 5 wires. The remaining 3 can be tied off or trimmed.

Configuration

Once you have completed all wiring, it is time to configure the UniMatrix.

If available, download the TVS file created by Tubbutec; this should contain all necessary settings. If not, here are some specific configuration details that may differ from default values or that you might wish to change (e.g., MIDI channel):

• Midi Base Note: We recommend +12 or +24. No change is necessary if you prefer the default.
• Stimulus/Input Count: 5
• Number of notes to populate: 37

Once you input this information, press the "rotated" button.

Navigate to the OUT 8 tab and ensure the Note/CC Column descends in the following order: 7, 15, 23, 31, 39.

Go to the top of the page and export the sysex file or send the configuration directly from the web application. This completes the UniMatrix installation.

Optional: MIDI-CV Filter Control

Tubbutec's UniMatrix adds 2 MIDI-CV controller opportunities. We have only used this feature to control the SEM filter.

To add filter control via MIDI, follow these steps:

1. In the configurator, scroll to the bottom and change CV1 mapping to "Controller".
2. Under Note/CC, change the value to 74, which is the standard "brightness" control in MIDI.
3. Attach a wire to I/O pin 23 on the UniMatrix, or use the extra set of wires included with the kit.
4. On the other end of this wire, add a resistor and connect it to the filter summing node on the SEM. The filter summing node op-amp is located directly above the filter molex header, which is connector H.
5. Since the UniMatrix only supplies CV from 0-5 volts, we need to double the voltage for the summing node. This is typically achieved using 100k summing resistors, as the SEM filter requires 0-10V for a full sweep. Solder one leg of a 50K resistor to pin 2 of A19 (a 741 op-amp). Solder the other end of the resistor to the wire coming from the UniMatrix.
6. To add control of both filters, simply run a second wire before it connects to the resistor. This second wire should go to SEM 2 and connect via another 50K resistor in the same manner.

Tip: For true duophonic SEM fun with CC control, you can assign CV 2 to a different CC number and run pin 24 from the UniMatrix just like described above to the second SEM. This allows individual control of each filter. Alternatively, you can use velocity to achieve more dynamic expression from your TVS via MIDI.

Additional Hint: MIDI Clock Output

The UniMatrix includes a MIDI clock output. Connector H on the mini sequencer allows for external clock input; however, the pulse must be above 12V, meaning you would need to convert the signal using transistor logic.