Hi-Z refers to “hi-impedance”, it is a setting that optimizes the input impedance on Spark MINI. Turn it off for low-output pickups, and turn it on for high-output pickups.
You can turn on the High-Z mode on the Spark MINI in the Spark app by following the steps below:
1. Make sure the Spark MINI is connected to the Spark app via Tone Control.
2. Tap on the Spark MINI product card on the Menu page, then turn the Hi-Z mode on: