4
LI0083 – Revision 22 June 2017
General Description
The G.R.A.S. 12AU Power Module is a supply and conditioning amplifier for simultaneously
powering a preamplifier for a condenser microphone and an amplifier for a loudspeaker or any
other sound source using a loudspeaker/earphone/coupler. By design, it avoids system-generated
noise, e.g. from ground loops. In a measurement set-up, the 12AU controls both the paths of the
signal sent out to the loudspeaker and the resulting acoustic signal picked up by the microphone.
In both cases, its set-up for handling these signals independently comes under external control.
The 12AU is remote controlled entirely via its USB interface, and, for this purpose, is delivered with
a control program for Microsoft Windows
®
. Settings on the 12AU can be controlled by the control
software’s graphical user interface and easily confirmed by the LEDs on the front panel. See “Using
the Graphical User Interface” on page 23 for instructions. It is also possible to operate the 12AU
typing commands in its
View Log
window, see “Operating the 12AU Using Commands” on page
28.
It is optimized for computerized production line testing. Up to six 12AUs can be connected to and
operated from the same PC.
Features
•
Single channel conditioning amplifier for microphone preamplifier and speaker amplifier with
measurement of current output
•
Controls the paths of the outgoing and received signals at the same time
•
Very low inherent noise
•
The speaker input and the analogue outputs are floating with respect to common ground to
avoid system-generated noise
•
Measurement of loudspeaker impedance without disturbing the speaker
•
Fulfils EMC requirements according to EU regulations
•
Full remote control via USB interface
•
LEMO input with 200 V polarization voltage for externally polarized microphone
•
CCP input for prepolarized microphone
•
Gain settings for noise and overload control:
– Microphone conditioner: 0 to 50 dB in 10 dB steps
– Speaker amplifier: –20 dB to +10 dB in 10 dB steps
– Current output: 0 dB and +20 dB
•
Filters:
– Microphone amplifier: 1 Hz or 20 Hz
– Speaker amplifier: DC or AC coupling (10 Hz)
•
Comprehensive status and overload indication
•
Rack mountable in 19” rack.
