Gibson GA-20 Owner's Manual page 18

TURN IT ON
The Power Switch turns your amplifier ON and OFF.The "On/Off " switch glows when the
amplifier is turned on.
CAUTION: Your amplifier is not disconnected from the mains when the Power Switch
is in the OFF position.
PLUG YOUR GUITAR IN
First, turn the Volume knobs down – counterclockwise – as far as they will go.Then plug
your 1/4 inch plug (standard guitar cord) into one of the three inputs as described in the
"Front Panel" overview earlier.
SWITCH FROM "STANDBY" to "PLAY"
Make sure your volume is turned down before switching from "Standby" to "Play. " This avoids
sudden output which could harm your speakers.