GRAS 12AD User manual

Instruction Manual
12AD Power Module

Revision 29 10 2007

CONTENTS
1. Introduction and Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Polarization Voltage ................................................3
1.2 Power Supplies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.3 Input/Output ......................................................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. Specications ...................................................7

Power Module Type 12AD - Page 4
1. Introduction and Description
The G.R.A.S. Power Module Type 12AD (Fig. 1) is a portable, single-channel power supply for
use with microphone preampliers and condenser microphones. It provides:
• a polarization voltage for condenser microphones
• a voltage supply of ±15 V DC for powering microphone preampliers
1.1 Polarization Voltage
The polarization voltage can be set to either 0 V or 200V 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 12AD can run on batteries with a battery life of approximately 50 hours using G.R.A.S.
preampliers, or from an external power supply of 4.5 - 24 V DC (see section 3).
1.3 Input/Output
The Type 12AD has a 7-pin LEMO input connector for microphone preampliers such as the
G.R.A.S. Preampliers Types 26AM, 26AC and 26AK. This input connector is also compatible
with a range of microphone preampliers from other suppliers such as Norsonic, L&D and Brüel
& Kjær. The output signal of the microphone preamplier is available via a standard BNC socket
for direct use with analyzers, voltmeters, oscilloscopes etc. This output signal from the LEMO
input connector (pin 4 - see Fig. 2.2) is AC coupled to the BNC output connector.
Fig. 1.1 Power Module Type 12AD

Power Module Type 12AD - Page 5
2. External Features
2.1 Front Panel
The front panel has the following features (see also Fig. 2.1):
• 7-pin LEMO input connector for the microphone preamplier. Wiring diagram shown in Fig.
2.2.
• BNC output socket for output signal of microphone preamplier.
• 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 +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).
• 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 12AD
Fig. 2.2 7-pin LEMO female socket 1B (external view)
Power switch
Green LED
power OK
Red LED Batt.
Low
Input for micro-
phone preampli-
er using a 7-pin
LEMO connector
Output BNC
socket

Power Module Type 12AD - Page 6
3. Batteries and External Power
The Power Supply Type 12AD 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 12AD is switched on via the l– Oswitch
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 compart-
ment 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 12AD
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

Power Module Type 12AD - Page 7
making sure to observe the correct polarity as indicated in the battery drawer. Use alkaline bat-
teries 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 12AD (see section 3) but don’t switch it on
yet.
2. Select which polarization to use (200 V for an externally polarized microphone or 0 V for a
prepolarized microphone).
3. Mount the microphone on to the preamplier
Note: the microphone must be compatible with the polarization voltage selected in step 2.
4. Insert the LEMO plug of the preamplier into the Input socket of the Type 12AD.
5. Using a suitable lead, connect the Output socket of the Type 12AD to an analyzer, voltme-
ter, oscilloscope etc., and switch it on.
6. Switch on the Type 12AD.
7. Adjust the analyzer, voltmeter, oscilloscope etc. to gauge correctly the signal from the Type
12AD.
5. Service and Repair
Repairs should be carried out only by qualied personal. The Power Module Type 12AD should
not be dismantled with power on because of high-voltage circuits.

Power Module Type 12AD - Page 8
6. Specications
Input/Output:
Input: 7-pin LEMO 1B female connector for microphone preamplier
Output: BNC coaxial socket for output signal of microphone preamplier
Output impedance:
30 Ω
Frequency response:
± 0.2 dB: 0.05 Hz - 200 kHz
Preampliersupplyvoltages:
Preamplier: ±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:
35 mA with a G.R.A.S. preamplier
Battery life:
Approximately 50 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:
520 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.