An analog signal is one which is analogous, or similar in form, to the original source from which it was produced. An analog audio signal is one which varies with time in the same way as the air pressure of the original sound does.
Analog is contrasted with digital.
Analog is also used as a complementary term when describing the sound quality of an audio system. It is associated with a natural, realistic sound.
Analog audio sources include:
Vinyl records: Here the audio signal is stored in the wavy pattern of the record’s groove. The stylus of the phono cartridge follows this pattern and generates an analog electrical signal.
Magnetic tape: Here the audio signal is stored as a varying pattern of magnetisation on the tape. When the tape is played the tape head detects the variations in the magnetic field of the tape passing it and converts that varying magnetic field into an analog electrical signal.
©Wayne Butcher