Recording Handbook - Hol.gr

amplifier are, therefore, global EQ.
Q1.1.3 What is noise reduction? What is Dolby? What is DBX?
See the rec.audio.pro FAQ for incredible detail about this.
There are two major families of noise reduction technology which
you're likely to find on 4-tracks: Dolby and DBX. These are each
discussed in a paragraph below.
There are (at least) three varieties of Dolby on cassette decks, but
they all work more or less the same way: whilst recording, they
enhance the high frequencies in the same area where hiss occurs.
During playback, they reduce those frequencies back to the same level
they were originally. This also reduces the hiss. You can play back
a Dolby-encoded tape without Dolby; the only effect you'll hear will
be a brighter, higher top end.
DBX processes the sound more severely than Dolby [and more
effectively?? --DSF]. If you record using DBX, you *must* play back
with it on. You may even find that a DBX-encoded tape from one
machine does not replay exactly on another.
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