Adjust the output volume of the source instrument to normal operating volume, or sing into the microphone using your loudest level. Make sure that the Master volume and the channel volume on the T4S/T8S are set to 0. While playing your instrument/audio sources as loudly as you would during a performance, turn the Trim control on applicable channel of the T4S/T8S clockwise until the signal/clip indicator glows green. If the indicator flashes red or glows steady red, turn the trim control counterclockwise to decrease the level until it’s most always green.