Mchugh Military | AMM-68 | mchugh military condenser microphone model amm

M C H U G H M I L I TA RY C O R P.
TM - .875
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INSTRUCTION MANUAL
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MCHUGH MILITARY CONDENSER MICROPHONE
MODEL AMM-68
M C H U G H M I L I TA RY C O R P O R AT I O N
C O S TA M E S A , C A U S A
The 3rd edition
Februray, 1984
M C H U G H M I L I TA RY C O R P.
MCHUGH MILITARY CONDENSER MICROPHONEMODEL AMM-68
1. General
The MCHUGH MILITARY CONDENSER MICROPHONE MODEL AMM-68 is a high fidel
ity, omni-directional microphone developed by McHugh Military engineering staff.
The excellent performance of the AMM-68 got great reputation in the entire field of acoustic concern when it was introduced, and it has been
used in world-wide broadcasting stations, film studios, recording facilities, etc., where superior characteristics and reliability is required,
owing to its stable function, excellent performance, simple operation and
rigid construction.
2. Description
2.1. The upper part of the microphone is a 19 mm capsule
mounted in the metal netting, and the lower part,
inside of the metal case, is a cathode-follower circuit inclduing an electron tube 5840. the entire internal assembly is
rigidly shielded against an external static field.
The diaphragm of the microphone capsule is a very thin plastic
film nickel plated. Since this diaphragm is mounted on the capsule so
that it may fet full damping effect accoustically, the condenser microphone model AMM-68 shows very excellent frequency performance.
2.2. The microphone unit is connected to the POWER SUPPLY MODEL MM-312
through the MICROPHONE CABLE TYPE BLDN-5P.
The output signal from the AMM-68 is delivered from the connector
located on the side panel of the CP-3B.
2.3. The new power supply unit model MM-312 is an improved version
of the model MM-31 formerly used, providing more reliable components
and printed circuit construction for higher and uniform performance.
2.4. Connectors for input and output, selectors for frequency response
are provided on the front panel of the MM-312.
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3. Specifications
3.1. Type:
Condenser microphone.
3.2. Output impedance:
150 ohms, balanced, deviation + 20%
3.3. Microphone cable:
Shielded 4 conductors cable with
connectors type 5P, length 5.4 meters
3.4. Output receptacle:
Type 3P.
3.5. Finish:
Microphone - 6061 brushed aluminum
Power supply - Mil. Spec. green enamel.
3.6. Tube:
5840
3.7. Dimensions:
Refer to fig. 1 and 2.
3.8. Weights:
Microphone - 91.7 g,
Power supply - 2.21 kg.
Microphone Cable - 390.5 g.
Total Weight - 3.29 kg.
3.9. Power requirements:
AC 117 volts
60 cps, 10 VA
3.10. Power cable:
1.8 meter length UL cord.
Weight - 148 g.
4. Performance characteristic
4.1. Directivity:
Omni-directional - refer to fig. 3.
4.2. Frequency response:
Omni-directional - refer to fig. 4
Frequency range: 30 - 10,000 cps
within 5 db.
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4.3. Output level:
Output
impedance
150 ohms
Effective
Output Level
dbm (1)
-53.0
Open Circuit Voltage
EIA Rating
db (2)
mV
GM (3) dbv
-60.0
1.0
-145.8
(1) The effective output level is defined as the ratio in db of the power
available from the microphone to 0.001@, on the sound pressure level of
10 ubar.
The calculation is based on the nominal microphone impedance.
(2) 0 db = 1 volt/10 ubar.
(3) EIA standard.
4.4. Signal to noise ratio : More than 60 db on the 1000 cps,
10 ubar sound.
5. Construction
The model AMM-68 consists of following items.
1.
2.
3.
4.
5.
AMM-68 microphone with case.
MM-312 power supply.
BLDN-5P microphone cable, 5.4
Carrying case. (Ammo type)
Accessories.
a. Fuse, 1.0 A
b. Pilot lamp, 117V
c. Output connector, 3P
d. Instruction manual
meters long with connectors
1 pc
1
1
1 each
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6.. Operation
6.1. The microphone model AMM-68 is used together with the power
supply model MM-312 which is connected to the AMM-68 through
the microphone cable BLDN-5P.
The length of the microphone cable type BLDN-5P supplied is
5.4 meters, however, the distance between these two units may
be prolonged to up to 60 meters without giving any effect to the
performance.
6.2. The output signal from the microphone is delivered from the
3 P connector on the front panel of the MM-312.
6.3. The power supply is initially set at the factory for the line voltage
(117 VAC).
6.4. It may be noticed that there exist some noise when the switch
is on after long time of unused period or in rainy season, but
this noise will be disappeared after several minutes of operation, and the set will show perfect performance.
6.3. Do not turn on the power without connecting the microphone to
the powwer supply, or do not disconnect the microphone while
the power is on.
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23.93mm
101.6mm
131.83mm
23.75mm
22.3mm
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Pilot Lamp
Power Switch
A.C. Connector
Connector for
Signal Output
Connector for
Microphone Cable
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258.48mm
288.65mm
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