Operator`s manual

Model VR240 Audio Logging Recorder
January 2000
4-1
CHAPTER 4
THEORY OF OPERATION
Section I. PHILOSOPHY OF OPERATION
4-1. GENERAL.
While the VR240 is similar in some ways to ordinary tape recorders, many of its features are
unique to logging recorders in general and digital logging recorders in particular. This section
explains aspects of the VR240 that may not be obvious, but with which you should be familiar in
order to make the best use of the unit’s capabilities.
NOTE
Most of the following discussion involves a comparison between
analog and digital recording to tape. Once a signal is converted
to digital form, recording amounts to simply storing data on the
media (whatever it is). Therefore, much of the discussion applies
to any type of media, including magneto-optical disks and DVD-
RAM.
4-2. COMPROMISES IN LOGGING RECORDERS.
Ordinary recorders are judged mainly for sound quality, and are rarely called upon to record
more than an hour at a time. Logging recorders are judged mainly for the ability to fit as much
material as possible on a given amount of tape, and are rarely called upon to play more than an
hour at a time. When we do listen to a logging recorder we listen for content and intelligibility
rather than “audiophile quality.” A logging recorder is a compromise, trading sound quality for
quantity.
4-3. ANALOG vs. DIGITAL RECORDING.
In analog tape recording, audio is stored by magnetizing the tape in direct proportion to the
audio signal. While this process can achieve excellent quality, anyone who has made a copy of
a copy knows that some degradation is inevitable. The magnetization process is not precise,
and any variation in tape speed is audible as unsteadiness in the sound.
To maximize sound quality in an analog recorder, you run tape at a high speed and you keep
the tape tracks as wide as possible while maintaining separation to avoid crosstalk; in other
words, you use a lot of tape. To maximize recording time and channels you do exactly the
opposite: run the tape slowly and jam as many tracks as you can across the width of the tape; in
other words, you use as little tape as possible. Reducing the amount of tape used to record an