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Setup
The preamplifier has four sets of input connections, two sets of output connections, an input
selector and three level controls. Optionally, it also has a remote control.
It also has an AC line power connection. The amplifier's voltage and current rating are
indicated on the rear. It will be either 240 volts, 120 volts, or 100 volts. A .5 amp 3AG slow
blow fuse is provided with 100-120 volt units, and a .25 amp slow blow fuse is provided with
220-240 volt units. The frequency rating of the power supply is 50 to 60 Hz. The
preamplifier typically draws 25 watts during operation.
We have provided a standard AC power cord which fits into the line receptacle at the rear.
The preamplifier is equipped for operation with an earth ground provided by the AC outlet.
Do not defeat this ground. The chassis and circuit ground of the preamplifier is connected to
earth through a power thermistor, which gives a ground connection but helps avoid ground
loops.
The four input connections on the rear are pairs of XLR and RCA connectors with right and
left channels indicated. If your signal source is balanced, you may use the XLR input
connectors. On these connectors, pin 1 is grounded, pin 2 is the positive signal input, and
pin 3 is the negative signal input.
If your signal source is unbalanced, input will occur through the RCA input connector, which
is in parallel with the XLR connections 1 and 2. For operation with unbalanced inputs, a
shorting plug is provided between pins 1 and 3, shorting the negative input to ground, and
providing optimal performance.
The unbalanced input impedance of the preamplifier is a nominal 10 kOhms. In balanced
mode, the input impedance is higher, with a differential impedance of 20 kOhms.
Next to the inputs on the rear panel, the preamplifier offers tape outputs through both XLR
and RCA connectors. This output is a direct connection to inputs 1, 2, and 3 when they are
selected from the front panel. Input 4 is deliberately not available through the tape output
connection. Input 4 is designated for use with a tape recorder if you have one, and we have
arranged that it will not place its output on the tape out, which will prevent you from
accidentally creating a feedback connection with your tape machine.
At the left hand side (viewed from the rear) of the rear panel, two male XLR connectors and
two RCA connectors are used for the main output. On the XLR, pin 1 is ground, pin 2 is
positive, and pin 3 is negative. The RCA connector's ground is in parallel with pin 1 and the
RCA hot is attached to pin 2. You may use either of these connectors for balanced or
unbalanced operation.
The circuitry of the preamplifier is such that it will drive any impedance without distortion,
however as the load impedance goes down, you will experience a reduction in gain. The
preamplifier will act as a maximum plus and minus 20 ma current source into a dead short.
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