Oberheim GM-400, Руководство по эксплуатации

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Oberheim GM 400
Digital Signal Processor
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optimum operating range, between -12 dB and -3 dB. Press Exit to return to the main video
page.
The input signal level can also be constantly monitored from the main video page, using the
bars on the left of the display and illustrated below:
input level
Output level.
The MASTER LEVEL (general output level) shown on the main video page:
must be regulated in the same way as the input level in order to adapt the output volume to
that of the equipment connected to the OUTPUT(S). Since this parameter can also be
memorized, more details of how it operates will be described in later sections.
Digital technology and levels.
The GM 400 is an all-digital instrument: this means that some simple rules have to be followed
during programming.
In the digital technology, the maximum permitted dynamic threshold is 0 dB; above this level,
even if it is only reached and exceeded for one moment, so-called digital distortion is created.
Digital distortion has nothing to do with the distortion often required by guitarists, and
generates an extremely unpleasant effect often mistakenly thought to be a real malfunction of
the equipment. Since the GM 400 is equipped with filters with an operating range of +/- 14 dB
and it is possible to add together the action of a number of filters operating simultaneously, the
threshold of 0 dB may be exceeded. This must therefore be borne in mind when programming
the GM 400, with frequent checks on the amplification gain introduced by the filters mentioned
above by means of the bypass functions described in the PLAY MODE and EDIT MODE
sections.
Adjusting the display contrast.
The GM 400 is equipped with a large backlit LCD (liquid crystal display). In view of the
characteristics of the LCD system, the contrast has to be adjusted to suit the angle from which
the operator looks at it. A trimmer marked CONTRAST on the left of the panel is provided for
this purpose.