. "When Marty McFly entered the garage to play his guitar, he turned up the volume and overdrive knobs all the way. Playing a single \"power chord\", he was suddenly thrown backwards into a bookcase, and blew the speaker out. Seconds later, Doc called his own home, warning Marty \u2014 too late \u2014 that it might overload."@en . "When Marty McFly entered the garage to play his guitar, he turned up the volume and overdrive knobs all the way. Playing a single \"power chord\", he was suddenly thrown backwards into a bookcase, and blew the speaker out. Seconds later, Doc called his own home, warning Marty \u2014 too late \u2014 that it might overload. Some time after returning to 1985, Marty repaired and upgraded the blown-out speaker to be more accommodating and resilient to his high-decibel requirements. By May 1986, it was up for sale. Marty used the amplifier to trick Biff Tannen, sending him across the room, and allowing Marty to take Doc's notebook from him. Fortunately, no visible damage was done to the amplifier."@en . . . "CRM-114 amplifier"@en . . . . . . .