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For Mustang GT, Mustang GTX, Rumble Stage and Rumble Studio users updating their Universal Tone app from the 3.X version to the 4.X
version, it is important to unpair Bluetooth devices on your amp first. To do this, on your amp you will need to:

Press menu

Select WiFi & Bluetooth

Select Bluetooth

Select Unpair Devices

Select Yes

Reboot amplifier

Note: This will clear all of the Bluetooth connections with your amp
 
Keywords: Universal, Tone, update, firmware