Many kinds of audio insulators are used to better the sound quality of stereophonic equipments, but their effects seem not always better in improvement of sound quality. In this study, to clarify how the insulator affects on stereophonic equipments, first we consider how works the insulator to the loaded equipment from view point of mechanical vibration induced on stereophonic equipments related with a AC power transformer, CD drive mechanism and radiated sound from loudspeakers etc. Next, we evaluate experimentally its effects on noise suppression of stereophonic equipments and finally we carried out a listening test of represented sound. Consequently, the insulator is effective to reduce inevitable vibration and electrical noise on stereophonic equipments and to improve the sound quality and summing localization under standard stereophonic representation.