Blackstar Mkiii Head for electric guitar. The head is essentially the amplifier, but without the speaker to reproduce the sound. It is not necessary to connect the head to a speaker in order for it to work, but in order to practice, you will need to connect headphones or speaker cabinet. A head can be used for practice at home as well as for rehearsal/recording in a studio or live performances. In this case, it has a power of 20W.