R a d i o S y s t e m s , I n c .
D A - 2 / 4 x 4 b M a n u a l
5 / 0 7
P a g e 4
Overview
The Radio Systems DA-4x4b is designed to function as a super low noise, low
distortion audio distribution amplifier which may be user wired to function in various
flexible input and output configurations.
Excellent isolation is provided between outputs. Each balanced channel, regardless
of level set and load, is unaffected by the other channels. The Radio Systems DA-
4x4b Distribution Amplifier allows audio sources to be routed to multiple locations
with various level requirements and impedances while maintaining the integrity of
signal quality throughout.
The distribution amplifier is configurable to a dual channel, 2x4 output version, or
quad channel, 4x4 output version.
Mounting
The 4x4b occupies only 1 rack unit (1-3/4 inch) of height in a 19 inch EIA rack. To
allow for adequate ventilation, avoid mounting the unit directly above large heat
producing equipment such as power amps or power supplies.
When stacking units, it is recommended that one rack space (1-3/4 inch) remain
open between every three units.
Operation
Apply an input level of approximately 0dB to the input terminals. The gain of any
stage may be increased by 20dB in 10dB steps by changing the internal gain straps.
To locate and reset these jumpers, refer to the parts layout for the location of JU1
and JU2. The lid of the unit must be removed to access these jumpers. Place a
shorting strap across the center and rear pin (pin towards the rear barrier strip) to
increase input gain by 10dB. Place a shorting strap across the center and forward
pin to increase input gain by 20dB.
Output level is factory set for unity gain. Each output can be individually set via its
front panel recessed level pot over a range from –60 to +18dBm. Nominal
operating levels are 0dBm input and +10dBm output. Higher operating levels can
cut dynamic range by operating too close to the clipping point. Adjust each output
to the desired level, keeping clipping in mind.
Connections
The units are primarily designed for balanced inputs and outputs. The input ground
is connected to the chassis and power supply at a single point. If unbalanced lines
are used, tie the unused input terminal to ground. However, do not tie any unused
output terminals to ground. Wire an unbalanced output between one output
terminal and the input ground terminal. For further details, see the section on
using active balanced circuitry in this manual.
Although the outputs are short circuit protected, operating into less than a 600 ohm
load is not recommended. The input is bridging (high impedance) and will not load
