Front Panel Controls And Indicators; Power; Input Level Control; Output Level Control - Art PRO MPA User Manual

can cause the PRO MPA to produce a ÒthumpÓ on power up
and power down.
If the PRO MPA fails to power up when the power switch is
turned on, check to see that its power cord is plugged into an
active outlet. If the unit still fails to operate properly, turn it off
and unplug it. Then consult your dealer or A R TÕs Customer
Service department.
FRONT PANEL CONTROLS & INDICATORS

Power

The Power switch supplies and removes power from the unit.
The PRO MPA should be powered ÒonÓ with all monitor levels
turned down, or off, to protect against any ÒthumpingÓ caused
by high gain settings. Likewise, the PRO MPA should be turned
ÒoffÓ after turning all monitor levels down.

Input Level Control

The Input Level Control sets the amount of input gain of the
PRO MPA. Turn the control clockwise to increase gain and
counterclockwise to decrease gain. You may control two ranges
of gain with this control, +26 to +60dB and +6 to +40dB.
Selection of the gain range is made with the +20dB gain switch.
When setting the Input Level Control, refer to the 10 segment
Tube Character Array for a visual reference to the PRO MPAÕs
internal signal levels (applied gain).

Output Level Control

The Output Level Control sets the output level of the PRO MPA.
When the control is fully counterclockwise, there is no output
Level. Turning the control clockwise increases the level of the
output to a maximum of +10dB of gain. This gain is in addition
to the existing input gain. When setting the Output Level
Control, refer to the Vu Meter for an accurate level leaving the
PRO MPA.

+20dB Gain/ Norm Switch

Use the +20dB Gain/ Norm switch to set the gain range of the
Input control. When the switch is in the out (Normal) position
the gain range is +6 to +40dB. Depressing the switch adds
20dB of gain. With the switch in, the gain range is +26 to
+60dB. With most microphone applications youÕll find using the
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PRO MPA with the +20dB gain switch in is needed. Use the set-
ting that best fits your application.

Phase Switch

The Phase Switch is provided to reverse the phase of a signal.
This switch works on Pins 2 and 3 of the XLR Output jack of the
channel. The Phase switch also reverses the polarity of the 1/4Ó
output jack. In the Normal position, the signal is in-phase. In the
Reverse (or ÒinÓ) position, Pins 2 and 3 are reversed as the sig-
nal is changed to 180 degrees out of phase. The Phase LED
will illuminate when the Phase Switch is in its ÒreverseÓ position.
In multiple microphone applications, the placement of the micro-
phones can affect the phase of a signal. If two microphones
pick up the same signal from different locations, the result can
be a hollow or frequency ÒshiftedÓ sound. In some cases it may
sound as if an instrument disappears if it happens to be 180
degrees out of phase. Depressing the Phase switch of one
channel can remedy this problem. Likewise, if a microphone
cable is wired incorrectly, when used with a properly wired
cable the signal will be out of phase.
**Note: for single microphone applications switching the phase
switch in and out will produce little to no change in the output
signal.
Phantom Power Switch
Each channel of the PRO MPA can power any microphone
needing +48 volts DC Phantom power. The Phantom power is
engaged and disengaged with this switch. The Phantom Power
LED will illuminate when Phantom Power is ÒonÓ. Phantom
power is supplied to pins 2 and 3 of the XLR input jack.
**Note: Be sure to turn down or mute the output of the PRO
MPA when engaging or disengaging Phantom power.
Additionally, when disengaging, allow 30 - 45 seconds for the
power to completely dissipate. Most microphones will make a
sound like air leaking from a tire when phantom power is dis-
connected, but some can make some very nasty low rumbles
and whines as well.
**Another Note: Dynamic microphones should not be affected
or damaged if they are plugged into a line where Phantom
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