Graph Tech Ghost Pin 7 Output Harness
If you are installing the Hexpander without the Acousti-phonic, you may want to add this optional pin-7 wiring harness so that your guitar's mag and/or piezo signal goes down the 13-pin MIDI cable and out the back of the converter. That way, you don't need a 1/4" cable plugged into the guitar.
Most MIDI converters have two 1/4" outputs on the back -- one for MIDI, and one for this pin-7 signal.
The Pin-7 Output Harness is required if you're installing the Hexpander without the Acousti-Phonic, and are adding the Quickswitch. It enables the QuickSwitch to control the mag output on your synth module. Otherwise, the Hexpander and the mags exist as two separate systems. The Pin-7 Output Harness links the two pickup systems in the absence of the Acousti-Phonic.
The 1/4" output jack on your guitar will remain unchanged, and you can use it with a 1/4" patch cord if you just want to play your mags through a guitar amp. Overview of Hexpander output options (PDF)
Note that the acoustic signal on pin-7 of the 13-pin jack is the raw piezo signal, which requires post-processing outside the guitar to make it sound like an acoustic guitar. For realistic, studio-quality acoustic guitar sound from your electric guitar, install the Acousti-Phonic.
The Acousti-Phonic, if you're installing that too, provides this same feature and makes the pin-7 harness unnecessary.
Here is a schematic of how all connections should look. Pin7Harness