Roland AC-90 Guide D'utilisation page 9

Phantom Power
Because they have a comparatively wider range and better
sound quality than dynamic mics, condenser mics are often
used for miking acoustic guitars. However, they require a
power source to operate. Although some condenser mics run
off batteries placed within the mic housing, in many cases a
type of power supply known as "phantom power" is
required. This power supply uses the existing mic cable to
feed power.
The AC-90's phantom power is output at a constant 48 V, so
it conforms to professional specifications required at
recording studios.
5. SELECT Button
This switches the input level to match that of the connected
device (mic or line).
You can connect guitars with magnetic pickups when LINE
is selected with the SELECT button.
* Note that the volume is increased if the switch is set to "MIC"
when you have a line-level device connected.
6. VOLUME Knobs
(GUITAR CHANNEL)
Adjusts the volume of the GUITAR channel.
* To accommodate the lower output of piezo pickups, the volume
level when the VOLUME knob is between the 7 and 10
positions is set somewhat higher when the PICKUP button is
set to PIEZO in comparison with the MAGNETIC setting.
(MIC/LINE CHANNEL)
Adjusts the volume of the MIC/LINE channel.
* When using the AC-90 with the GUITAR channel and MIC/
LINE channel mixed, adjust the volume balance between the
two channels with the VOLUME knob.
7. BASS Knobs
Adjust the level of the low-frequency range.
8. MIDDLE Knobs
Adjust the level of the midrange.
Names of Things and What They Do
9. TREBLE Knobs
Adjust the level of the high-frequency range.
The tone of an acoustic instrument can vary immensely from
one instrument to the next. The kind of sound required also
varies according to how an instrument is being used in a
particular ensemble. Actively use the BASS, MIDDLE, and
TREBLE knobs to adjust the tone to suit the instrument you
are using and the conditions in which it is being used.
(Example)
• When using the AC-90 with the speaker stand attached,
you may want to turn up the BASS knob so the lower
range is perceived better.
• If the sound seems too harsh, such as immediately after
changing strings, you may want to turn down the
TREBLE knob to cut back on the high frequencies.
10. CHORUS Buttons
Switch chorus on and off.
When on, the indicator is lit.
You can use a foot switch (the optional BOSS FS-5U) to
switch chorus on and off. Turning chorus on and off with the
foot switch works on both channels.
11. CHORUS Knob
Turn this knob to select among the three types of chorus
(SPACE, RICH, and WIDE).
You can adjust the amount of effect applied by changing the
position of the knob.
* This is enabled when the CHORUS button is in the ON
position.
* The markings indicating the SPACE and RICH positions are
approximate. Listen to the sound to confirm the effect as you
make adjustments.
SPACE
This is a spacially synthesized chorus. With spacially
synthesized chorus, a method available only in stereo, the
chorus effect is created by taking the sound from the right
speaker (from which the effect sound is output), and the
sound from the left speaker (which outputs the direct sound),
and then mixing them in the actual space. This creates a
greater lateral spread than that produced when the sounds
are mixed electronically, providing a more natural sense of
breadth.
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