3 Heads Are Better Than 2

A tape head functions as a small electromagnet powered by the audio signal.
The current flowing through it produces a magnetic field which changes the
magnetic state of the tape particles.

For playback, this process is reversed: The magnetic field
of the tape is read, producing an electrical current in the head.

A 2-head cassette deck uses a single head for both the recording and
playback. A 3 head deck, on the other hand, has a head for each
purpose (erase, record, play - in that order).

This allows you to listen to the signal on a tape immediately after it was
recorded.  This process (called monitoring) is useful for checking the
quality of a recording in progress, and for making fine adjustments to
signal level and bias.  If these changes are made, however, I suggest
you start that particualr tape again from the start.

Return to my homepage.