Electrical - mechanical - sound. From electrical energy, electricity is passed unto an amplifier, a microphone or a cdplayer is connected to the amplifier. The amplifier then change the sound entering it into mechanical energy. Then sound is passed out through a speaker cable givin sound energy

Transfer means to allow through (science-transmit e.g a window and light energy. the light energy is transmitted through) and so if the energy wasnt allowed through there wouldnt be a current or circuit because the energy would be lost i the amplifier

The benefits of an electric guitar amplifier are the increased energy content to the signal the guitar produces and the available tone controls. The amplifier is a staple of guitarists for those reasons.

they use electrical and sound energy

NO. THE UNIVERSAL LAW STILL APPLIES -- ENERGY CANNOT BE CREATED NOR DESTROYED -- ONLY TRANSFORMED.

Actually in amplifier we give it the Vcc,Vee,Vbb which is such value from which the gain of an amplifier cannot increase till the point of Vcc,it holds the law of conservation of energy but if gain reaches to Vcc then it is in cutoff region so,never the amplification process violate the law of conservation of energy

Actually in amplifer we want the required phase shift+amount of required voltage from sources present so this is actually the use of amplifier that it enhances our strength over particular shape waveform and magnitude at required point