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 magnetic and/or piezo signal goes down the 13-pin MIDI cable and out the back of the converter.
This allows to only connect all of your signals out the 13 pin jack and into the MIDI unit. Then you can use the guitar output on your convertor to run your magnetic and/or raw piezo signal to your regular amplifier.
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 of the 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.