|bias & equalization|
|Analogue magnetic recording media (magnetic
tape, cassettes, magnetic film, etc.) has a non-linear response to the
range of frequencies in the audio spectrum
bias is a high
frequency signal which shifts the audio into a higher frequency range where
the tape is more linear in its response. Equalization
is filtering applied to the signal to correct this non-linearity.
Both must be adjusted for each different brand of media and calibrated often.