Hx1-Hx2 Manual-1.4.1 - Telos

2.4 Input Audio Connection
The input connection, SEND IN, has the following characteristics:
♦ XLR Pin 1 = Ground,
♦ XLR Pin 2 = High (Active Balanced, RF suppressed)
♦ XLR Pin 3 = Low (Active Balanced, RF suppressed)
♦ Bridging impedance, > 100K Ohm
♦ Analog clip point at +24 dBu
♦ Analog-to-Digital converter resolution of 24 bits
♦ Adjustable input level from -10 to +8 dBu
♦ Switchable LINE and MIC level input range
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The unit can accommodate a line input level between -10 dbu and +8 dBu, adjustable with
a trim pot on the rear panel. The input level is set to +4 dBu level from the factory. A +4dBu
signal fed into the SEND IN connector should light the Yellow LED bargraph segment on the
Front Panel.
If more input gain is needed, turn the trimmer CLOCKWISE to increase the gain to match the
operating level of the hybrid.
Increasing the send level beyond a normal meter reading does not increase the level into the telco
line due to the hybrid’s AGC and limiting. You will only add distortion and degrade the hybrid’s
performance. There is a dip switch configuration option that applies an extra 3dB gain after the AGC,
should you need more send level.
Next to the input level pot is a pushbutton switch that selects between line and mic levels.
When the pushbutton switch is in the LINE position (out), the input range of the SEND IN
signal is –10 to +8 dBu. When the switch is in the MIC position (in), the input range of the
SEND IN signal is –70 to –52 dBu.
The inputs are designed to be sourced from balanced lines. Usually shielded cables have the
shield wire connected only on one end (most often the input) to prevent ground loops. Older
equipment with a transformer output stage may need a terminating resistor across pins 2 and 3
to maintain a proper “flat” frequency response; consult the manual for your equipment for how
to use it with high impedance inputs.
If you are connecting a device with an unbalanced output to your Hx, connect the shield from
the output of your device to pin 1 (ground) on the Hx input, and the “hot” lead from your
unbalanced output to pin 2 (high) on the Hx. Depending on the device, you might also want to