level before the trim control, preamplifier overload can be avoided. It is best to
leave the trim control fully clockwise for normal recording operations.
II. INSTALLATION
A. AUDIO TERMINATIONS
1. 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.
2. Output connections are made via male XLR connectors with pin 2 positive, pin 3
negative and pin 1 ground. 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 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
SHIELD
HOT
GND
(OPEN)
3
Figure 1. UNBALANCED OUTPUT CABLE TERMINATION
3. The balanced output driver is capable of driving a matched 600
Ω
line. This type
of termination can be very advantageous for driving very long lines because it
provides maximum power transfer through the cable. With a higher power music
signal, aberrations caused by distributed capacitance and inductance in the
cable are minimized which improves transient performance and harmonic
integrity. To create a 600
Ω
balanced line, simply connect a 301
Ω
1% metal film
resistor between pins 2 and 3 at the destination end of the cable. This
termination combines with the preamplifiers 300
Ω
output impedance to provide a
matched 600
W
line.
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