Sigma ADA-21 Instruction Manual

ADA-21

AUDIO

DISTRIBUTION AMPLIFIER

INSTRUCTION MANUAL

SIGMA ELECTRONICS, INC.

P.O. Box 448

1027 COMMERCIAL AVENUE

EAST PETERSBURG, PA 17520-0448

[phone]

ADA-21 AUDIO DISTRIBUTION AMPLIFIER

GENERAL:

The ADA-21 Audio Distribution Amplif ier is designed to provide s ix (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 c onfiguration dependent on the requirement of the
destination equipment.

This module m ust be installed in a Sigma Frame for pr oper operation. Power is provided by the power
supply within the frame. A Sigma frame is designed to ac c ommodate 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 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-21 module can reside in any of four different frames or Stand-Alone box provided by Sigma
Electronics, Inc. If this module is pur chased as a component of a system, please r efer to the SERIES 2100
FRAMES Instruction Manual. If the module was purchas ed separately, an existing frame m ust 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 f rame provides two (2) slots for dual

module configurations; i.e. stereo audio.
♦ The SS-2100-6 frame is designed f or 19 inch EIA r ack installations . It provides six (6) slots f or m odules in
1 rack unit of space.
♦ The SS-2100-12+ fram e 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 f rames is available. Please r efer to the special section on frames if
this was purchased as a com plete s ystem. 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 im pedance 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: Ther e are s ix ( 6) outputs on the r ear panel of the unit. Eac h output is des igned to drive a 600Ω
load.

1

­C

INPUT

+

AUDIO CONNECTOR REAR PANEL CONNECTIONS

Figure 1 Figure 2

­C
+

OUTPUT

ADA-21 Doc. No. – 13911

2 3

­C
+

4

­C
+

­C
+

5 6

­C
+

­C
+

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ADA-21