ART PRO MPA II User Manual

PRO MPA II ™

ART PRO MPA II Microphone Preamplifier

USER’S GUIDE

IMPORTANT SAFETY INSTRUCTIONS – READ FIRST

alerts you to the presence of uninsulated you to important operating and maintenance
dangerous voltage inside the enclosure. Voltage instructions in the accompanying literature.
that may be sufficient to constitute a risk of shock. Please read manual.

Read instructions:

Retain these safety and operating instructions for future reference. Heed all warnings printed here and on the equipment.
Follow the operating instructions printed in this user guide.

Do not open:

Aside from two vacuum tubes, there are no user serviceable parts inside. Refer any service work to qualified technical
personnel only.

Power sources:

Only connect the unit to mains power of the type marked on the rear panel. The power source must provide a good
ground connection.

Power cord:

Use the power cord with the mains plug appropriate for your local mains supply as provided with the equipment. If the
provided plug does not fit into your outlet consult your service agent. Route the power cord so that it is not likely to be
walked on, stretched or pinched by items placed upon or against.

Grounding:

Do not defeat the grounding and polarization means of the power cord plug. Do not remove or tamper with the ground
connection on the power cord.

Ventilation:

Do not position the unit where the air required for ventilation is impeded. If the unit is to be operated in a rack, case or
other furniture, ensure that it is constructed to allow adequate ventilation.

Moisture:

To reduce the risk of fire or electrical shock do not expose the unit to rain, moisture or use in damp or wet conditions. Do
not place a container of liquid on it, which may spill into any openings.

Heat:

Do not locate the unit in a place close to excessive heat or direct sunlight, as this could be a fire hazard. Locate the unit
away from any equipment, which produces heat such as: power supplies, power amplifiers and heaters.

Environment:

Protect from excessive dirt, dust, heat, and vibration when operating and storing. Avoid tobacco ash, drink spillage and
smoke, especially that associated with smoke machines.

Handling:

To prevent damage to the controls and cosmetics avoid rough handling and excessive vibration. Protect the controls from
damage during transit. Use adequate padding if you need to ship the unit. To avoid injury to yourself or damage to the
equipment take care when lifting, moving or carrying the unit.

Servicing:

Switch off the equipment and unplug the power cord immediately if it is exposed to moisture, spilled liquid, objects fallen
into opening, or the power cord or plug becomes damaged during a lightning storm or if smoke odor or noise is noted.
Refer servicing to qualified technical personnel only.

Installation:

Install the unit in accordance with the instructions printed in the user guide.

This symbol, wherever it appears, This symbol, wherever it appears, alerts

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IMPORTANT SAFETY INSTRUCTIONS – READ FIRST ......................................................... II

PRO MPA II OVERVIEW – FEATURES AND GENERAL INFORMATION:............................ 1

FRONT PANEL CONNECTIONS AND CONTROLS ................................................................ 3

Input Gain control ..................................................................................................................................... 3

Input Impedance control ........................................................................................................................... 4

Low Cut Filter control................................................................................................................................4

Gain switch ............................................................................................................................................... 4

Phantom switch ........................................................................................................................................ 5

Phase switch............................................................................................................................................. 5

Plate Voltage switch ................................................................................................................................. 5

Mid/Side Matrix switch .............................................................................................................................. 6

Analog Output control ............................................................................................................................... 6

STEREO/Dual switch................................................................................................................................ 6

+4/-10 switch (rear panel)......................................................................................................................... 7

Meter Trim ................................................................................................................................................ 7

Front Panel connections .........................................................................................................7

Instrument Inputs ...................................................................................................................................... 7

Rear Panel connections ..........................................................................................................8

Balanced Inputs ........................................................................................................................................ 8

Balanced Outputs ..................................................................................................................................... 8

PRO MPA II OPERATING INSTRUCTIONS ............................................................................ 9

Obtaining the best noise performance with the PRO MPA II.................................................................... 9

Adjusting the Input Impedance ................................................................................................................. 9

Setting the Tube Plate Voltage ............................................................................................................... 10

Using the Mid/Side mode........................................................................................................................ 11

WARRANTY INFORMATION.................................................................................................. 12

Limited Warranty..................................................................................................................................... 12

Exclusions............................................................................................................................................... 12

SERVICE ................................................................................................................................. 13

PRO MPA II SPECIFICATIONS ............................................................................................. 14

List of Figures

Figure 1 – Block Diagram .......................................................................................................... 2

Figure 2 – Front controls............................................................................................................ 3

Figure 3 – Rear connections ...................................................................................................... 8

Figure 4 – Mid/Side Mic alignment........................................................................................... 11

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PRO MPA II OVERVIEW – FEATURES AND GENERAL
INFORMATION

:

The ART PRO MPA II microphone preamplifier features a new low noise, high performance preampli-

fication circuitry, designed for superior audio fidelity. Building upon the quality and success of great

sounding products like the Pro MPA and MPA GOLD, ART engineers set out to develop the next

generation of professional microphone preamplifier. PRO MPA II is the culmination of years of re-

search and development, and sets a new standard for quality and value. Professional features and

spectacular tone are what make the PRO MPA II a world-class microphone preamplifier. Its impres-

sive feature set includes:

• Variable input impedance for flexible microphone voicing (150 Ohms to 2400 Ohms).

• Selectable plate voltage

• Large VU meters

• Front accessible meter trim

• Discrete class A input microphone preamplifier

• Low noise at low gains

• Low THD

• Wide frequency response

• Front accessible Instrument Input Jack

• Very high input impedance

• Mid/Side micing support

• +4dBm/-10dBV output level selection

• Switch selectable Stereo/Dual operation of the output controls

• Automatically switches to the instrument input when you plug in

The signal path of PRO MPA II consists of a discrete class A microphone pre-amp followed by a Low

Cut Filter, a balanced differential tube circuit with a 20dB Gain switch and then the phase switch. The

Mid/Side Matrix switch sums the adjacent channel to decode left and right information following the

gain switch function and before the output level control. The Tube Warmth display monitors the signal

level before the output level control as well. The analog meter monitors the output level of the PRO

MPA II before the +4/-10 switch but after the output level control.

The PRO MPA II is an attractively styled processor, with a black anodized front panel and matching

knobs. The switches on the PRO MPA II are backlit and illuminate when depressed.

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Figure 1 – Block Diagram

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FRONT PANEL CONNECTIONS AND CONTROLS

Figure 2 – Front 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 ad-

justed from 0dB (for line level signals) to 40dB of gain.

The analog meters are used to see the effects of the input gain setting.

Additional gain is available via the Gain switch (+20dB) and the Analog Output control (+10dB) for a

maximum of 70dB 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 PRO MPA II . Refer to the section titled “Obtaining the best noise performance

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