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ADA-21S STEREO AUDIO DISTRIBUTION AMPLIFIER
ADA-21 Doc. No. – 14466
Page 1 of 3
GENERAL:
The ADA-21S Stereo Audio Distribution Amplifier is designed to provide three (3) dual-channel outputs
from a stereo audio signal source. The module is compatible with either balanced or unbalanced audio signals
on the input and outputs. Outputs can be mixed between balanced and unbalanced configuration dependent
on the requirement of the destination equipment.
This module must be installed in a Sigma Frame for proper operation. Power is provided by the power
supply within the frame. A Sigma frame is designed to accommodate any 2100 Series module. This allows the
ADA-21S to be resident with any other Sigma 2100 Series module in a common frame.
POWER:
The ADA-21S operates from bus voltages of unregulated +20Vdc and -20Vdc. These voltages are supplied
by the Sigma frame / power supply. The module regulates the bus voltage to +15Vdc and -15Vdc. Circuit
protection is provided by PTC Thermistors (Positive Temperature Coefficient Thermal Resistor) which serve
as a permanent fuse. Upon correction of the fault, the PTC Thermistor will reset.
FRAMES:
The ADA-21S module can reside in any of four different frames provided by Sigma Electronics, Inc. If this
module is purchased as a component of a system, please refer to the SERIES 2100 FRAMES Instruction
Manual. If the module was purchased separately, an existing frame must be present for proper operation.
Sigma would like to emphasize the fact that any of the Series 2100 modules can be mixed in any frame.
♦ The SS-2100-2 frame is also designed for desk top applications. This frame provides two (2) slots for dual
module configurations; i.e. stereo audio.
♦ The SS-2100-6 frame is designed for 19 inch EIA rack installations. It provides six (6) slots for modules in
1 rack unit of space.
♦ The SS-2100-12+ frame provides thirteen (13) slots for modules within 3 RU. Redundant power supplies
are provided within this frame.
♦ The SS-2100-16+ frame is also available for installations in a 19 inch EIA rack. This frame provides
seventeen (17) slots for modules within 3 RU.
Additional information on the various frames is available. Please refer to the special section on frames if
this was purchased as a complete system. If this information is not provided with this shipment, contact Sigma
Electronics for assistance.
CONNECTIONS:
Wiring to the module is performed via detachable screw terminal connectors (Figure 1).
INPUT: There are dual-channel inputs on the rear panel of the unit; the first and last connectors (Figure
2). The Right channel is on the left (or top if mounted vertically) and the Left channel is on the right as seen
from the rear of the unit. Both inputs are a high impedance configuration. This allows the audio signals to be
bridged to other units. To ensure proper impedance matching it may be necessary to terminate the outputs
with a 600Ω load. It is recommended that, if termination is necessary, use a 600Ω, 1/2 watt resistor across the
(+) and (-) outputs. When multiple units have inputs bridged to the same source, only apply the 600Ω resistor
to the last unit in the line.
OUTPUT: There are three (3) outputs on the rear panel of the unit for each channel . Each output is
designed to drive a 600Ω load. Since each output on a channel is identical, the numbering is only provided for
the operator’s convenience.
AUDIO CONNECTOR REAR PANEL CONNECTIONS
Figure 1 Figure 2
INPUT L
ADA-21S
-
C
+
INPUT R
1
2
3
3
2
1
-
C
+
-
C
+
-
C
+
-
C
+
-
C
+
-
C
+
-
C
+