The optional extra ‘Wet’ pedal will also allow you to toggle the dry signal off completely and use your guitar is a string or organ-like pad. The options are endless for what you can create with the Plus Pedal.

Here's what Gamechanger say about the Wet Pedal

The special WET footswitch goes into the DRY output of the PLUS PEDAL.
When the WET ONLY mode is engaged, the main output will have no DRY output, which allows you to create some very interesting sound effects and even transform your guitar into something like an organ or a cello or a synth pad.

The Footswitch also has an output jack, therefore if you still wish to use a second amp with the DRY output – you can plug a basic jack – jack cable into the Footswitch.