9
Grounding options: In certain installations, it may be desirable to separate the
preamplifier signal ground from the power supply chassis and earth grounds. Noise
inducing ground loops can be broken while retaining the safety feature of the grounded
AC power cord. The 801R should not be operated with a ground lift or "cheater" plug on
the AC power cord. Simply set the AUDIO GND toggle switch on the rear panel of the
power supply unit to the desired setting (ISO or EARTH).
REMOTE UNIT POWER CONNECTION
The RCU is powered with the supplied AC wall adapter. It is recommended that the I
2
C
data connections be made before applying power to the RCU. Simply plugging the
2.1mm barrel connector into the DC power jack turns the power on. The AC wall adapter
is rated for 7.5V / 1A DC. (+) is in the center and (–) is on the outside sleeve.
AUDIO CONNECTIONS
Input connections are made via female XLR connectors with pin 2 positive, pin 3
negative and pin 1 ground. 48V phantom power is supplied on pins 2 and 3.
Output connections are made via male XLR connectors with pin 2 positive, pin 3
negative and pin 1 ground. An additional set of parallel outputs is provided with a 25 pin
D-sub connector. Both sets of output connectors can be used simultaneously.
If the output is to be used unbalanced, pin 1 should be connected to signal ground and
pin 2 to signal hot. Due to the nature of the balanced output stage, pin 3 should be left
open for unbalanced operation. See figure below. Note: This will provide a signal of
positive absolute polarity when the preamplifier is being used with a microphone which
produces a positive voltage on pin 2 with positive air pressure on the front of the
diaphragm. While a vast majority of microphones conform to this standard a few do not.
Use the phase reverse switch to compensate if necessary.
1
2
3
SHIELD
HOT
XLR FEMALE
Figure 6. Unbalanced output cable termination
