ART Digital MPA™ Microphone Preamplifier
NOTE: the Input impedance control only affects the cannon connector inputs. The 1/4” instrument input on the front
panel is NOT affected by this control in any way. The instrument input impedance is ALWAYS >
1M Ohm.
Dynamic microphones are affected as much as phantom powered units.
We provide a continuously variable impedance control to allow you to fine-tune the voicing, finding
the perfect interaction between microphone and pre-amp.
Start by setting the centering the Input Impedance knob. This provides a 600-Ohm load.
Lower impedance loads will reject more noise picked up by cabling, and dampen microphone
resonance. Lower impedances tend to focus the sound more. Higher impedance settings provide
a more “open” sound.
Obtaining the perfect digital level setting
The Digital level meter indicates both peak and average levels present at the A/D converter. The
0dB LED indicates that there is less than 1dB of headroom before clipping. The highest peak level
reached is held for 1 second by a single LED and the average level is indicated by the remaining
LEDs, lit in series.
It is recommended you start with the digital level control centered. Adjust the input gain and +20dB
switch such that the digital meter holds peaks at –3dB and occasionally hits the red 0dB LED. This
setting will provide the best dynamic range AND the tube will saturate before the A/D clips (on
heavy overloads).
If you want more tube headroom, set the digital level control fully clockwise.
If you need to compress the input signal before it is converted to a digital signal, use the rear panel
Insert Jacks. The insert point is located between the tube output and the Digital Level control. This
allows insertion of a dynamics processor with the ability to tweak the A/D input sensitivity from the
DMPA front panel.
Setting the Tube Plate Voltage
The DMPA allows the user select between one of two vastly different tube bias and power supply
levels. The transition between either setting is smooth and quiet and the gain variation is minimal.
NOTE: It takes 15-30 seconds for the tube circuit to fully transition between either mode. During this time, the unit
passes a signal and the only noticeable change is a slight increase in level in the “HIGH” setting.
The “Warm” setting produces a smooth transition from very clean low levels up to a “round” satu-
rated clipping on peaks. This setting is reminiscent of old tube gear, and used to get the most
tube-like sound out of the unit. Common uses include tracking with instruments.
The “High” setting of the plate voltage switch has increased bandwidth and headroom, very low
distortion and runs extremely clean until it reaches a point of saturated clipping. The clipping is
well controlled and still sounds natural. This setting is incredible on vocals.
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