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3. ON ADJUSTMENT OF INPUT GAIN AND OUTPUT ATT
The INPUT GAIN knob is used to adjust the level in the analog portion before the A/D
converter. The OUTPUT ATT knob is used to adjust the level in the analog portion after
the D/A converter. They are not interlocked with the mode and programs described later.
With these knobs, the user can adjust the relation between the level of the sound signals
input to the SRP-F700, head room of the SRP-F700, and the output level of the device
when it is connected to other equipment.
For digital audio equipment in general, the head margin in the digital range is related to
the actual resolution of digital sound signals. The smaller the head room, the fewer the bits
wasted in a finite bit length.
Accordingly, the sound quality is improved when the head room of the signals input to the
A/D converter is set at the lowest possible level to the extent that the full scale is not
exceeded at the maximum input and there is no clip in the digital signal processing.
To produce a good sound quality, the SRP-F700 device has an INPUT GAIN knob for
adjusting the head room for the signals input to the A/D converter at the input stage. With
this knob, the user can adjust the gain of the input signals on the front stage of the A/D
converter. The user can adjust the INPUT GAIN while checking the head room with the
INPUT level meter and the OVER indicator on the panel.
The maximum value of the input level meter, +24 dBs, is the maximum input level of the
SRP-F700 device. This level meter does not indicate the level of the signals input to the
SRP-F700, but indicates the level plus the input gain determined by the INPUT GAIN
knob @. For example, when the input level is +6 dBs, and INPUT GAIN knob is set to 3,
the level meter indicates 9 dB (= 6 dBs + 3 dB). The head room in this instance is 15 dB
(= +24 -9).
The level meter can not follow up peak signals but can confirm the clip of peak waves
with the OVER indicator. The OVER indicator indicates that the input signal peak has
clipped, exceeding the maximum input level of the D/A converter.
It is necessary to decrease the input level when the OVER indicator lights up
continuously.
The device has an OUTPUT attenuation knob corresponding to the INPUT GAIN
adjustment.
When the gain of the input signals is adjusted with the INPUT GAIN knob, all the
succeeding output signals will also have a gain. To prevent this, the OUTPUT ATT knob
is set at the same position as the INPUT GAIN so that the output is attenuated by the same
GAIN quantity used in the input portion. By this, the relation between the input and output
level of the device is kept at 1:1.
This knob is not necessarily used in combination with the INPUT GAIN knob. It may also
be used to adjust the output level.
The OUTPUT level meter indicates the level of the signals that have passed the OUTPUT
attenuation and OUTPUT level.
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