background image

ADA-21

Doc. No. – 13911

Page 1 of 3

ADA-21  AUDIO DISTRIBUTION AMPLIFIER

GENERAL:

The ADA-21 Audio Distribution Amplifier is designed to provide six (6) outputs from a single 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-21 to be resident with any other Sigma 2100 Series module in a common frame.

POWER:

The ADA-21 operates from bus voltages of unreg20Vdc 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-21 module can reside in any of four different frames or Stand-Alone box 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.

  When assembled in a stand-alone box, it is assigned the model number ADA-26A. This is a desk top box.

  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 twelve (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

sixteen (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 is a single input on the rear panel of the unit (Figure 2). The INPUT is a high impedance

configuration. This allows the audio signals to bridge to other units. To ensure proper impedance matching it
may be necessary to terminate the outputs with a 600

 load. It is recommended that, if termination is

necessary, use a 600

, 1/2 watt resistor across the (+) and (-) outputs. When multiple units have inputs

bridged to the same source, only apply the 600

 resistor to the last unit in the line.

OUTPUT:  There are six (6) outputs on the rear panel of the unit. Each output is designed to drive a 600

load.

AUDIO CONNECTOR

REAR PANEL CONNECTIONS

Figure 1

Figure 2

AD

A-

21

-
C
+

INPUT

OUT

P

UT

1

2

3

4

5

6

-
C
+

-
C
+

-
C
+

-
C
+

-
C
+

-
C
+

Reviews: