Applied Research and Technology (ART) Digital MPA Owner's Manual
ART Digital MPA™ Microphone Preamplifier
TABLE OF CONTENTS
Introduction ............................................................................................ 3
Introduction .......................................................................................... 3
Features............................................................................................... 3
Front Panel Controls .............................................................................. 4
Input Gain Control ............................................................................... 4
Input Impedance Control ................................................................. 4-5
Analog Output Control ......................................................................... 5
HPF Control ........................................................................................ 5
Gain Switch ......................................................................................... 5
Phantom Switch ................................................................................... 5
Phase Switch ...................................................................................... 5
Plate Voltage Switch......................................................................... 5-6
Meter Switch........................................................................................ 6
Digital Section Controls ........................................................................ 6
Digital Level Control ............................................................................ 6
Dither Switch ....................................................................................... 6
Sample Rate Control ........................................................................... 7
Optical Switch...................................................................................... 8
Front Panel Connections......................................................................... 8
Instrument Inputs................................................................................. 8
Rear Panel Connections......................................................................... 8
Balanced Inputs................................................................................... 8
Balanced Outputs ............................................................................... 8
Insert Jacks ......................................................................................... 9
Word Clock Jacks................................................................................. 9
ADAT Input .......................................................................................... 9
Optical Output....................................................................................... 9
S/PDIF Output ..................................................................................... 9
AES/EBU Output .................................................................................. 9
Signal Path Flow ................................................................................... 10
Signal Path Flow Diagram .................................................................. 10
Operating Instructions ......................................................................... 10
Obtaining the best noise performance............................................... 10
Adjusting the input impedance...................................................... 10-11
Obtaining the perfect digital level setting ........................................... 11
Setting the tube plate voltage ............................................................ 11
Warranty Information ........................................................................... 12
Service .................................................................................................. 12
Specifications ....................................................................................... 13
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ART Digital MPA™ Microphone Preamplifier
DIGITAL MPA INTRODUCTION
The ART Digital MPA™ microphone preamplifier features a new low noise, high performance preamplification
circuitry, designed for superior audio fidelity. Building upon the quality and success of great sounding products like
the Pro MPA, ART engineers set out to develop the next generation of professional microphone preamplifier. The
Digital MPA is the culmination of years of research and development, and sets a new standard for quality and value.
Professional features and spectacular tone are what make the Digital MPA a world-class microphone preamplifier.
DIGITAL MPA FEATURES:
• Variable input impedance for flexible microphone voicing (150 Ohms to 2400 Ohms).
• Selectable plate voltage
• Large VU meters
• Front accessible meter trim
• Selectable between output level and tube warmth
• Improved discrete class A input microphone preamplifier
• Lower noise at low gains
• Lower THD
• Wider frequency response
• Front accessible Instrument Input Jack
• Very high input impedance
• Automatically switches to the instrument input when you plug in
The Digital MPA also features digital connectivity for use with various digital processors and digital recording devices.
The Digital interface supports the following features and functions:
• 24-204KHz External sample rate
• 44.1K, 48K, 88.2K, 96K, 176.4K, 192K Internal sample rates
• 24/16 bit switchable dithering
• Wide dynamic range A/D
• Rotary Encoder for quick selection of sample rate and output format
• Separate analog and digital output level controls
• Digital Level LED meters
• ADAT optical I/O
• Sync to incoming ADAT data rate
• Switch selectable optical output (S/PDIF or ADAT)
• Selectable Pro/consumer output format
• AES/EBU output on cannon connector
• Two wordclock jacks allowing loop through
ART Digital MPA – Rear view image (above)
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ART Digital MPA™ Microphone Preamplifier
FRONT PANEL CONTROLS
Input Gain Control
This control optimizes the input signal level before the tube gain is applied. Both Microphone and
Instrument input gains remain the same and are affected by this adjustment. Input gain can be
adjusted from 0dB (for line level signals) to 45dB of gain.
Use the analog meters in the TUBE setting to gauge how much input gain is required.
Additional gain is available via the Gain switch (+20dB) and the Analog Output control (+10dB) for
a maximum of 75dB total.
The combination of these controls allows the user to adjust the signal level through the tube
section, providing more or less “tube” sound as needed. To obtain more “tube’ sound, increase
input gain, use the +20dB Gain switch, “normal” plate voltage, and less Analog output gain.
Both the microphone and instrument inputs are optimized for their respective sources as far as
signal levels and noise performance. Running most of the gain on the input generally provides the
best performance of the DMPA. Refer to the section titled “Obtaining the best noise performance
with the DMPA” for more detailed instructions on setting the Input Gain control for the best results.
Input Impedance Control
This knob controls the Mic/line input amplifier impedance. This function allows variable voicing of
any microphone.
Refer to the application section titled “Adjusting the Input Impedance” for more information on
making the most of this function.
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ART Digital MPA™ Microphone Preamplifier
The 1/4” instrument input is NOT affected by this control, and remains high (>1M Ohm) impedance.
Analog Output control
The output signal level at the rear output jacks is adjusted by this control. It can provide from
+10dB of gain (fully clockwise) to completely muted. You can see the effects of this adjustment
reflected in the analog meters when the meter switch is set to “output”.
HPF control
The HPF is a single tuned High Pass Filter that is frequency tunable. The input signal can be
filtered to remove “pops” or other extraneous low frequency information. This control moves the
rolloff frequency from 10 Hz (fully CCW) to 200 Hz (fully CW). Since it is single tuned (the same
as single pole, the simplest kind of filter), it preserves some low frequency content so its use is
less obtrusive. It is especially useful in close mic’d applications.
Gain switch
The Gain switch is used in conjunction with the input gain control to adjust signal levels through
the DMPA. When depressed, the tube circuit provides 20dB more gain in the signal path. This also
has the effect of driving the tube harder and making the tube the dominant source of gain and
overload character.
Phantom switch
Phantom power on the microphone input is turned on and off with this switch. Depressing the
switch will power condenser microphones and other 48volt phantom powered devices. Phantom
power is supplied to pins 2 and 3 of the input jack.
NOTE:
1) Dynamic microphones are NOT affected by Phantom power, although it should be turned off when using dynamic
microphones or line level inputs.
2) Although the 48volt phantom power ramps up and down slowly it may still create a pop. Mute the output of the
DMPA when engaging or disengaging phantom power to prevent damage to equipment following the DMPA.
Phase switch
The Phase switch can invert the phase of the audio signal path in either channel. The Phase
switch is located after the tube circuit in the signal path, so you can hear slight differences between different phase selections in the “normal” plate voltage mode near saturation. There are a
number of reasons why adjusting the phase is needed these include, wiring errors and inversions
in some audio equipment. Some microphones sound different depending on the phase chosen.
If two microphones are out of phase, they may cancel at various frequencies (depending on the
distance between them). If this happens, try changing the phase of one of the microphones and
see if there is an improvement.
Plate Voltage switch
This switch sets both the tube bias point and the plate voltage level the balanced differential tube
circuit runs at. The amount of headroom is adjusted by using the Gain switch and the input Gain
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