Microphone Preamplifier

Download User Guide PDF

General Description

Sound Devices’ MP-1 is a portable, battery-powered microphone preamplifier with phantom power. Designed for high-resolution fi eld production, this studio-quality mic pre is ideal for critical radio, television, and film production applications.
With its rugged mechanical and electrical construction, compact size and high-quality components, MP-1 will provide years of superb audio performance under the most punishing field conditions.

Features

Audio Performance 

• Maximum of 66 dB of gain, adjustable in eleven discrete steps for accurate, repeatable gain settings 
• Dynamic range exceeding 120 dB 
• 20 Hz to 50 kHz audio bandwidth
• High immunity to RF interference due to transformers, RF filtering, and all-metal construction 
• High current line output driver capable of driving very long cable runs

Transformer-Balanced 

• Premium quality input transformer provides superior sonic quality and freedom from interference problems 
• Custom-designed output transformer provides line driving ability with freedom from interference problems

Limiter 

• Extended range peak limiter via dual opto-isolators makes unit virtually “unclippable”

Battery Powered

• Internal battery power (two AA) for convenient, low cost power
• Battery life greater than 24 hours (phantom power off)

Durable Mechanical Construction 

• High strength extruded aluminum chassis with protective metal end rails to withstand punishing field conditions
• Easy access battery compartment for quick battery changes

Phantom Power 

• Selectable 48-volt and 12-volt phantom power for condenser and dynamic microphones

High-Pass Filter 

• Two selectable corner frequencies, 80 and 160 Hz, 6 dB per octave

Front Panel Controls and Indicators 

1. LIMITER/Peak LED

   Bi-color LED illuminates red at 3 dB below clipping; illuminates amber to indicate limiter activity

2. LIMITER Switch 

   Activates the peak limiter. Limits to +17 output.

3. High-Pass Filter Switch

   Three-position switch selects inserts an 80 Hz or 160 Hz corner frequency filter, 6 dB per octave. Center position of switch removes the filter from the signal path.

4. Rotary Gain Switch

   Selects the amount of gain from input to output, adjustable in 11 increments. 

5. POWER Switch 
   Powers the unit when switch is in the up position.

6. POWER LED 

   Bi-color LED illuminates green when the unit is powered and changes to red when approximately four hours of battery life remain.

Back Panel Connectors and Controls

7. BATTERY Compartment

   Requires two AA batteries for operation. Insert positive (+) end of battery first.

8. LINE OUT

   Transformer balanced XLR line-level output. +22 dBu peak output level.

9. PHANTOM Power Switch

   Three-position switch selects either 48-volt or 12-volt phantom power. Center position turns 
   phantom power off.

10. MIC IN

    Transformer-balanced XLR input accepts 
    microphone level signals.

Operational Notes

Transformers

The isolation characteristics of transformers are superior to other balancing techniques for the adverse and uncontrolled environments of fi eld production. Transformers provide complete galvanic isolation from the driving source, meaning there is no direct electrical connection. Signals are “transformed” magnetically. Both the transformers in the MP-1 use premium magnetic core material to achieve high signal handling capability (especially at low frequencies) while keeping distortion to a minimum. Because of their inherently high common mode impedance, transformers are unrivaled by any other type of input for common-mode noise rejection. 

Both the input and output of the MP-1 can be balanced or unbalanced without any problems. When unbalancing (either input or output) ground pin-3 to pin-1. There is no change in gain with an unbalanced connection into or out of the MP-1.

Phantom Power 

Microphones that require phantom power should use the lowest voltage acceptable to maximize battery life. Electret-condenser microphones that can operate on phantom voltages from 11–52 volts will not have any performance benefit using 48-volt phantom; therefore 12-volt phantom is appropriate. Microphones requiring 48-volt phantom will not operate, or may operate with lower headroom and increased distortion, at 12 volts, therefore use 48-volt phantom. Consult your microphone documentation. 

Dynamic microphones typically do not require phantom power. A properly connected balanced, dynamic microphone will, typically, not be affected by the presence of phantom power nor will it draw any current. However, it is good practice to turn phantom power off if the microphone cable is suspect. Poor or incorrectly wired microphone cable can cause audible artifacts in the microphone signal. (Phantom is an excellent cable tester.)

High-Pass Filter 
The two positions of the high pass filter (low cut) in the MP-1 are useful for removing excess low frequency energy in the audio signal. The 80 Hz position is appropriate when recording general speech, music, and ambient sound. The 160 Hz position is useful to enhance speech clarity. The high pass filter is a single pole design, 6 dB per octave.

When possible, attempt to equalize at the sound source with microphone selection, use of a windscreen, 
microphone placement, and onboard microphone fi ltering. A high pass fi lter on the microphone and a 
high pass filter on the MP-1 will give an additive effect, increasing the slope of the filter.

Limiter
The MP-1 has a built-in peak responding limiter which can be turned on or off by the switch on the front 
panel. The MP-1 limiter is really two completely separate limiters activated by the one switch; the first 
limiter keeps the input gain stage from clipping, and the second limiter limits the output to +17 dBu. The two limiters enable the MP-1 to limit in excess of 50 dB, meaning that it is very difficult to clip the unit, no matter the gain setting. The Limiter LED on the front panel illuminates in proportion to the amount of limiting.

Batteries 
The MP-1 is designed to operate on two AA alkaline cells for approximately 26 hours with typical signals (without phantom power). The audio performance of the MP-1 does not vary throughout the life of the batteries.

Many factors affect battery life including—battery chemistry, ambient temperature of operation, phantom voltage, microphone current draw, and output drive level. The chart below can be used as a starting point to estimate battery life. Experimentation is recommended to determine battery life for each individual setup. 

Note: Nickel-Cadmium batteries are not recommended in the MP-1 since these batteries have lower energy per cell than other types and will result in very short service.

Test conditions: 70 F, 42 dB gain with music source, 600 ohm load, +4 dBu output

FCC Statement 

This device has been tested and found to comply with the limits for a class B digital device, pursuant to part 15 of the FCC rules. These limits are designed to provide reasonable protection against harmful interference in a residential installation. This equipment generates, uses, and can radiate radio frequency energy and, if not installed and used in accordance with the instructions, may cause harmful interference to radio communications. However, there is no guarantee that interference will not occur in a particular installation. 

Warranty

Sound Devices, LLC warrants the MP-1 Microphone Preamp with Headphone Monitoring against defects in materials and workmanship for a period of ONE (1) year from date of original retail purchase. This is a non-transferable warranty that extends only to the original purchaser. Sound Devices, LLC will repair or replace the product at its discretion at no charge. Warranty claims due to severe service conditions will be addressed on an individual basis. THE WARRANTY AND REMEDIES SET FORTH ABOVE ARE EXCLUSIVE. SOUND DEVICES, LLC DISCLAIMS ALL OTHER WARRANTIES, EXPRESS OR IMPLIED, INCLUDING WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. SOUND DEVICES, LLC IS NOT RESPONSIBLE FOR SPECIAL, INCIDEN-
TAL, OR CONSEQUENTIAL DAMAGES ARISING FROM ANY BREACH OF WARRANTY OR UNDER ANY OTHER LEGAL THEORY. Because some jurisdictions do not permit the exclusion or limitations set forth above, they may not apply in all cases. 

For all service, including warranty repair, please contact Sound Devices for a return authorization number (RMA) before sending the unit for service. 

CE Declaration of Conformity

According to ISO/IEC Guide 22

Sound Devices, LLC
300 Wengel Drive 
Reedsburg, WI 53959 USA 

declares that the product, MP-1 is in conformity with and passes:

Tested by L. S. Compliance, Inc. Cedarburg, Wisconsin

December 16, 1999

Matthew Anderson

Director of Engineering
Sound Devices, LLC