Tape bias is the term for two techniques, AC bias and DC bias, that improve the fidelity of analogue tape recorders. DC bias is the addition of direct current to the audio signal that is being recorded. AC bias is the addition of an inaudible high-frequency signal to the audio signal. Most contemporary tape recorders use AC bias.
Visualization of the magnetic field on a stereo cassette containing a 1 kHz audio tone. Individual high-frequency magnetic domains are visible.
An audio tape recorder, also known as a tape deck, tape player or tape machine or simply a tape recorder, is a sound recording and reproduction device that records and plays back sounds usually using magnetic tape for storage. In its present-day form, it records a fluctuating signal by moving the tape across a tape head that polarizes the magnetic domains in the tape in proportion to the audio signal. Tape-recording devices include the reel-to-reel tape deck and the cassette deck, which uses a cassette for storage.
A reel-to-reel tape recorder from Akai, c. 1978
An early experimental non-magnetic tape recorder patented in 1886 by Alexander Graham Bell's Volta Laboratory.
Prototype of the Goodale tape recorder. The patent is based on this machine.
This tape recorder of Dr. Goodale is exhibited in the private Phonograph Museum in Mariazell, Austria.