Mustang GT + Fender Tone Support has a new home! Click here or go to https://www.fender.com/tone/support to visit our new support home. Related articles Fender® Guitar Amplifier Owner's Manuals (Archive) Contact a Fender Gear Advisor Fender® Guitar Amplifier Owner's Manuals (Current) I'm having trouble signing in, and I know my username and password are correct How do I update the firmware on a Mustang GT or Rumble digital amplifier?