Bias Frequency
The frequency of the high-frequency bias signal used when recording on analogue magnetic tape, usually expressed in kilohertz.
Record bias adds a high-frequency signal during magnetic recording to make the tape’s response to audio more linear. Bias frequency identifies the oscillator’s repetition rate. It differs from the amount of bias applied and from the recorded audio’s frequency range.
Bias Frequency — Cassette Deck
In a cassette deck, the bias oscillator supplies a signal above the audible range while the deck records. The stated frequency describes this circuit, not a tone you should hear or a setting to match to a music file. A combined bias-and-erase rating may describe a shared oscillator.
Compare the figure as a design specification, rather than treating a higher number as proof of better recordings. The bias calibration control normally changes bias level, not this frequency. Tape formulation, calibration and head condition still affect recording results; the playback frequency-response limit is separate.
Bias Frequency — Reel-to-Reel
In a reel-to-reel recorder, bias frequency belongs to the recording electronics. It supports magnetic recording on the chosen tape, while alignment sets the appropriate recording conditions for that tape and speed. A playback-only machine does not need a recording bias oscillator.
Compare oscillator figures separately from tape speed, audio response and calibration test-tone frequencies. Oscillator, audio-response and test-tone frequencies can all be stated in kilohertz, so their labels matter. Higher bias frequency alone does not establish lower distortion or greater recording bandwidth, and it does not replace correct tape and speed alignment.