The Effect Gizmo and Rack Gizmo are able to phantom power a Mastermind GT as long as you follow a few rules:

1). Use the Mastermind GT's power supply to power the Effect or Rack Gizmo, instead of using the supply that came with the Gizmo. The supplies included with the Effect Gizmo and Rack Gizmo don't provide enough current to power the Mastermind GT. A 12 volt DC supply with at least 3 amps of current capacity is recommended, such as this one.

2). Use the correct MIDI cable to connect the GT to the Gizmo. A 7-pin MIDI cable is the standard way to connect them. Some Effect Gizmos and all Rack Gizmos have a 6-pin XLR MIDI connector on the front panel. You can use an XLR6 to 7-pin MIDI cable to connect the GT to this connector. Additionally, the Mastermind GT/22 has an XLR6 MIDI output jack. You can use an XLR6 to 7-pin MIDI with all Gizmos, or an XLR6 to XLR6 MIDI cable to connect a GT/22 to Effect Gizmos and Rack Gizmos that have an XLR front panel jack.

Make sure your MIDI cable is good quality! The Mastermind GT draws a lot of current and the thin wire in cheap cables can cause a loss in voltage that will make the GT not function correctly. Symptoms of a bad cable or insufficient power supply include: the text of the GT displays fading out or turning entirely black, or the GT displays not lighting up.

Best-tronics is one company we recommend for high-quality MIDI cables. If your phantom power MIDI cable is 25 feet or longer, we recommend asking them for a cable made to our high current specifications. This is not listed as an item on their website, but it's available if you contact them by email.