Instruction Manual
Power Module Type 12AR
Skovlytoften 33, 2840 Holte, Denmark
www.gras.dk gras@gras.dk
SOUND & VIBRATION
G R A S
...
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Revision 08 09 2006
Power Module Type 12AR
G.R.A.S. Sound & Vibration
CONTENTS
1. Introduction and Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Polarization Voltages ...............................................3
1.2 Power Supplies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.3 Inputs/Outputs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. External Features ................................................4
2.1 Front Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2 Rear Panel .......................................................4
3. Batteries and External Power Supply ................................5
4. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5. Service and Repair ...............................................6
6. Specications ...................................................7
G.R.A.S. Sound & Vibration
Power Module Type 12AR - Page 4
1. Introduction and Description
The G.R.A.S. Power Module Type 12AR (Fig. 1) is a portable, dual-channel power supply for
use with microphone preampliers and condenser microphones. It provides:
• Polarization voltagees for two condenser microphones
• Voltage supplies of ±15 V DC for powering two microphone preampliers
1.1 Polarization Voltages
The polarization voltages can be set to either 0 V or 200 V via a switch on the rear panel (see
Fig. 2.3). This switch is latched to avoid inadvertently changing its setting. Just pull the latch on
the switch before changing the setting. Use:
• 0 V for prepolarized microphones, and
• 200 V for externally-polarized microphones
1.2 Power Supplies
The Type 12AR can run on batteries with a battery life of approximately 30 hours using G.R.A.S.
preampliers, or from an external power supply of 4.5 - 24 V DC (see section 3).
1.3 Inputs/Outputs
The Type 12AR has two 7-pin LEMO input connectors for microphone preampliers such as the
G.R.A.S. Preampliers Types 26AM, 26AC and 26AK. This input connector is also compatible
with a range of microphone preampliers from other suppliers such as Norsonic, L&D and Brüel
& Kjær. The output signals of the microphone preampliers are available via two standard BNC
sockets for direct use with analyzers, voltmeters, oscilloscopes etc. The output signals from the
LEMO input connectors (pin 4 - see Fig. 2.2) are AC coupled to the BNC output connectors.
Fig. 1.1 Power Module Type 12AR
G.R.A.S. Sound & Vibration
Power Module Type 12AR - Page 5
2. External Features
2.1 Front Panel
The front panel has the following features (see also Fig. 2.1):
• Two 7-pin LEMO input connectors for microphone preampliers. Wiring diagram shown in
Fig. 2.2.
• Two BNC output sockets for the output signals of the microphone preampliers.
• Power switch with two LEDs: green “OK”, red “Batt. Low”.
2.2 Rear Panel
The rear panel has the following features (see also Fig. 2.3):
• Input socket for an external voltage supply of 4.5 - 24 V DC; centre pin is +terminal.
• Twist/release holder for 160 mA low-impedance, slow-blow fuse.
• Latched switch for selecting a polarization voltage of either 0 V (for prepolarized micro-
phones) or 200 V (for externally-polarized microphones). Applies to both channels
• Detachable battery drawer for housing 4 alkaline cells LR 6 /AA. The use of an external
voltage supply automatically disables power from the batteries.
Fig. 2.1 Front panel of the Power Supply Type 12AR
Fig. 2.2 7-pin LEMO female socket 1B (external view)
Power switch
Green LED
power OK
Red LED Batt.
Low
Inputs for microphone preampli-
er using a 7-pin
LEMO connectors
Output BNC
sockets
G.R.A.S. Sound & Vibration
Power Module Type 12AR - Page 6
3. Batteries and External Power
The Power Supply Type 12AR can be powered either by internal batteries or from an external
power supply. If an external DC power supply is connected via the Ext. Supply socket on the
rear panel; any batteries inside the unit will automatically be disconnected.
The external power supply should be a mains/line adapter regulated to supply 4.5 - 24 V DC
with the centre pin as the + terminal. When the Type 12AR is switched on via the l – O switch
on the front panel, the green Power LED will light up, and the red Low Batt. indicator should
remain extinguished to ensure correct operation of the unit. If the Low Batt. LED lights up,
either the external power supply voltage is too low, or the batteries need changing. To ensure
valid measurements, we recommend that you change batteries whenever the Low Batt. LED is
lit; there will be at least one hour’s use left after it rst warns of low batteries.
To change the batteries, squeeze and pull out the battery drawer from the battery compartment on the rear panel (see Fig. 3.1). Remove all 4 batteries and replace them with fresh ones,
Fig. 2.3 Rear panel of Power Supply Type 12AR
Fig. 3.1 Battery drawer open: note polarity of batteries
Latched switch
for selecting
polarization
voltage:
0 V or 200 V
Input for external
power supply
4.5 - 24 V DC
Fuse 160 mA
low-impedance,
slow-blow
Battery drawer
for 4 alkaline
batteries LR
6/AA
G.R.A.S. Sound & Vibration
Power Module Type 12AR - Page 7
making sure to observe the correct polarity as indicated in the battery drawer. Use alkaline batteries size AA or LR6. Replace the battery drawer in the battery compartment.
If the fuse blows, rst rectify the cause then replace it with a new low-impedance slow-blow fuse
rated at 160 mA.
4. Operation
1. Make sure that power is available to the Type 12AR (see section 3) but don’t switch it on
yet.
2. Select which polarization to use (200 V for externally-polarized microphones or 0 V for prepolarized microphone).
3. Mount the microphones on to the preampliers
Note: the microphones must be compatible with the polarization voltage selected in step 2.
4. Insert the LEMO plugs of the preampliers into the Input sockets of the Type 12AR.
5. Using a suitable lead, connect the Output sockets of the Type 12AR to an analyzer, volt-
meter, oscilloscope etc., and switch it on.
6. Switch on the Type 12AR.
7. Adjust the analyzer, voltmeter, oscilloscope etc. to gauge correctly the signal from the Type
12AR.
5. Service and Repair
Repairs should be carried out only by qualied personal. The Power Module Type 12AR should
not be dismantled with power on because of high-voltage circuits.
G.R.A.S. Sound & Vibration
Power Module Type 12AR - Page 8
6. Specications
Inputs/Outputs:
Input: Two 7-pin LEMO 1B female connectors for microphone preampliers
Output: Two BNC coaxial sockets for the output signals of microphone
preampliers
Output impedance:
30 Ω
Frequency response:
± 0.2 dB: 0.05 Hz - 200 kHz
Preampliersupplyvoltages:
Preamplier: ±15 V
Polarization: 200 V (can be switched to 0 V when using prepolarized microphones)
Power supplies:
4 x LR6 (AA) standard alkaline cells or
Mains/line adapter supply regulated to 4.5 - 24 V DC
Power consumption:
45 mA with G.R.A.S. preampliers
Battery life:
Approximately 30 hours using alkaline batteries
(Valid at 23 ºC)
Fuse:
160 mA (Slow), 250 V
(Low-impedance fuse)
Operating temperature range:
–10 °C to +50 °C
Dimensions:
Height: 60 mm
Width: 105 mm
Depth: 130 mm
Weight:
540 g without batteries.
Accessories included:
EL0001: 4 x LR6 (AA) batteries
WEEE directive:
2002/96/EC
CE marking directive:
93/68/EEC
Manufactured to conform with:
RoHS directive:
2002/95/EC
G.R.A.S. Sound & Vibration continually strives to improve the quality of our products for our customers; therefore, the
specifications and accessories are subject to change.
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