The usual 'In's' are different in electrical impedance. If you don't know what this is, you are kindly asked to get yourself educated. In such environments it is usually not advised to connect different electrical circuitry without exactly knowing of the impact of your actions! The way out is to either make yourself acquainted with the basic knowledge of electronics, or go the easy consumer way - buy an adapter which decouples the aircraft electrics from your electronics.The usual commercial adapters - due to liability - must have this feature. So, short, buy one of the cables with the boxy electronics in line to get rid of the coupling issues.