The maximum input power of the FT1 is 500mW. In fact, the headphone output power under 1W input reaches 135dB, which has reached the auditory pain threshold of human ears. In addition, the U.S. NIOSH has defined a sound pressure limit that will not cause permanent hearing damage: within one hour of listening, the maximum sound pressure can not exceed 94dB; when the sound pressure reaches 127dB, theoretically, more than 1 second of listening will hurt the hearing. Therefore, from the hearing protection consideration, it is suggested that listeners should adjust the volume to an appropriate level to listen to music.