Oberheim DX/Stretch Installation

The Stretch is an expansion unit for the Oberheim DX digital drum machine that adds four new voices.
Front view, covers closed

Installing a Stretch is fairly simple, but requires some amount of skill with a soldering iron and knowledge of basic electronic assembly techniques. If you do not feel confident in these areas, please visit your local electronic repair shop for assistance.

The mechanical connections are simple. The left side panel on the DX is removed and reattached on the left side of the Stretch and the two metal cases are attached together with screws.

There are three types of electronic connections that need to be made between the Stretch and the DX:

  1. Two shielded audio cables between the front panel sections. Soldering required.
  2. Three power supply wires between main boards. Soldering required.
  3. Two ribbon cables between main boards. No soldering.
Connection overview

Audio Cables

The audio cables allow mixing the sound from the stretch into the main DX output. A connector on the Stretch has two shielded cables that should reach to the indicated area on the DX front panel. The cables should be soldered as shown below. The two cables may be interchanged to switch the voice panning from left to right.
Audio cable overview
Audio cable detail

Power Wires

Three color-coded wires lead from a connector on the Stretch to the main board of the DX. These carry the voltage to power the DX. Solder the ends of these wires as shown.
Power cable overview
Power cable detail

Ribbon Cables

The two ribbon cables carry control signals to the Stretch. The cables plug into IC sockets on the DX main board. Remove the integrated circuits (ICs) that are in the sockets where the cables will plug in. Take these ICs and plug them into the empty sockets on the Stretch circuit board right next to their corresponding cables.
Ribbon cables - Stretch end
Ribbon cables - DX end

In some of these photos, you may see other wires and ribbon cables. These are not related to the Stretch, but are a modification to the DX sync circuitry.

Thanks to G-Man for the photos!