UTILITY SUMMING & DISTRIBUTION AMPLIFIER
USDA 2X4 is a 2-in/4-out audio distribution amplifier that has the unique ability to combine as
well as "split" audio signals for distribution. The unit has two inputs (one stereo pair) and four
outputs (two stereo pairs). USDA 2X4 can be used as a 1X4 or 2X4 DA and can combine a
stereo input to a mono output(s) without degrading the separation of the stereo source signal.
All inputs are 20K bridging balanced; each output can drive a 600 ohm load to +26 dBm. An
output level adjustment is provided for each output channel. Overall gain is adjustable from -12
to +14 dB. Nominal input levels between -10 and +8 dBm are recommended. All USDA 2X4
circuitry is active and direct-coupled.
All audio connections are via the plug-in euroblocks. Remove about 1/8” of insulation, insert
wires into the plug, and tighten the screws. Be sure that no bare wiring is exposed.
Connect input signals to the USDA inputs, labeled "1" and "2". For unbalanced inputs, install a
jumper between the - input and GND. Single (mono) inputs may be fed to all 4 output channels
by connecting both 1 and 2 inputs in parallel. Connect output loads to USDA outputs, labeled 1
through 4. For unbalanced loads, connect to the + and GND terminals only. (Do not
the - terminal to ground.) It is not necessary to terminate unused outputs.
The signal fed to input 1 will appear at outputs 1 and 3. The signal fed to input 2 will appear at
outputs 2 and 4. Hence, outputs 1 and 2 are a Left/Right stereo pair, as are 3 and 4. Each
stereo output pair has a STEREO-MONO SWITCH. If the switch is in the "S" position, a stereo
input will produce a stereo output. If the switch is in the "M" position, that output will be
combined to monaural. The two stereo outputs operate independently; switching one output
pair to MONO has no effect on the other pair, and does not degrade the separation of the stereo
input signal. Each output has a gain adjustment for setting output level. A maximum of +8dBm
(average) is recommended. Input levels should be between -10 and +8 dBm. For input levels
outside of this range, consult the factory.
Input impedance 20K ohms balanced; 10K ohms unbalanced
Input levels -10 dBm to +8 dBm nominal
S/N ratio 100 dB, ref +4 dBm output w/ unity gain
Output source Z 100 ohms balanced; 50 ohms unbalanced
Output load 600 ohms or more per output, X4
Specifications subject to change without notice. P/N 3310 Rev. 6/04.
