Instruction manual

9-10
Section 9-6 - SAA-40S (Supervised Audio System Amplifier/Signal Circuit
Module, 40 Watts)
Wheelock, Inc. Part Number: 105493
The SAA-40S is a supervised audio system amplifier/strobe circuit module. It is capable of
providing 40 watts of audio amplification and a 24V, 2.0 Amp strobe NAC circuit for the
SAFEPATH
®
Panel. The amplifier section can select either a 25V or a 70.7V audio output. The
amplifier contains a switch mode power supply, a linear amplifier, and supervision circuitry.
The switch mode power supply is used to provide a constant DC voltage to the amplifier while the
input voltage is allowed to fluctuate over its operating range. The amplifier amplifies the low-level
600-ohm audio to 40 watts output at either 25V or 70.7V. The supervision circuit monitors field
speaker wiring integrity, field strobe wiring integrity, and amplifier functionality.
The board can be field configured for either 25V or 70.7V output. The configuration is done using
a two-position slide switch (S1) on the printed circuit board. The down position configures the
amplifier for a 25V output and the up position configures the amplifier for a 70.7V output. See
Figure 9-6 for switch location.
The amplifier supervises both the strobe field wiring and the speaker field wiring with a DC
current. The strobe field wiring is supervised with a reverse polarity technique, which applies a
DC voltage with one polarity to supervise the wiring and then reverses the polarity to energize the
strobes. The speaker field wiring is supervised with a DC current, which is removed when audio
is being played. Both field-wiring circuits are only supervised in the standby state. The amplifier
is supervised by monitoring the amplifier output for audio. The state of each of the three
supervision features is indicated via three LEDs on the printed circuit board. See Figure 9-6 for
LED locations.
There are two fuses on the printed circuit board, F1 and F2. Fuse F1 is the main fuse for the
entire board. F2 is the fuse for the strobe power. See Figure 9-6 on Page 9-11 for fuse locations.
Two UL LISTED 10K Ohm, 1W EOLR Resistors are included.
Fuse Rating
F1 10A
F2 3A
Nominal Specifications:
Rated Output @ 1kHz 40 Watts
Input Sensitivity 1Vrms
S/N Ratio 72dB
Frequency Response 275Hz to 6kHz
Input Voltage Range 24VDC
Supply Current (Standby) @ 24VDC 400mA
Supply Current (Full Load) @ 24VDC 3.6A
(Including 2.0 Amp Strobe Current)
Operating Temperature Range 0 to 49 Degrees C (32-120
Degrees F)