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ADA-21S STEREO AUDIO DISTRIBUTION AMPLIFIER
ADA-21 Doc. No. – 14466
Page 2 of 3
AUDIO CONFIGURATIONS:
The source and destination audio equipment must be evaluated to determine if they are Balanced or
Unbalanced. After determination is made, refer to the drawings provided to select the proper audio
configuration. The outputs can be any combination of balanced or unbalanced.
Balanced In to Balanced Out Balanced In to Unbalanced Out
Vout = Vin Vout = 0.5 Vin
Unbalanced In to Balanced Out Unbalanced In to Unbalanced Out
(-) Input Grounded; Vout = Vin Vout = 0.5 Vin
(-) Input Floating: Vout = 0.75 Vin
The input to output level comparison provided in the figures above, assumes the outputs are terminated
into a 600Ω load.
FRONT PANEL:
The adjustments and indicators on the front panel (Figure 3) can be accessed through the slots provided
in the frame in which the ADA-21S is installed. When mounted within the SS-2100 Series frames, it will be
necessary to remove the front panel of the frame to gain access to these items. Factory settings of the module
provide unity gain when terminated in 600Ω, and a bandwidth of 30 KHz.
Gain control for the right channel is achieved by adjustments to S01and R012. Gain control for the left
channel is achieved by adjustments to S901and R912. S01 and S901 provide gain adjustment in increments
of 6dB, while R012 and R912 provide fine adjustments of +/- 3dB. The positions of S01 make the following
adjustments to the gain level of the circuit - = OFF, 1= -6dB, 2= 0dB, 3= +6dB, 4= +12dB, 5= +18dBand 6=
+24dB.
Figure 3: Front Panel Gain Adjustment
+
C
-
IN OUT
+
C
-
+
C
-
+
C
-
ADA-21
+
C
-
IN OUT
+
C
-
+
C
-
+
C
Open
ADA-21
+
Gnd
IN OUT
+
C
-
+
C
-
+
C
-
ADA-21
+
Gnd
IN OUT
+
C
-
+
C
-
+
C
O
p
en
ADA-21
S01
R012
3
1
2
4
5
6
3
1
2
4
5
6
S901
R912