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 preampliers and condenser microphones. It provides:
• a polarization voltage for condenser microphones
• a voltage supply of ±15 V DC for powering microphone preampliers
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.
preampliers, 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 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 signal of the microphone preamplier 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
