Za 250-Lz Amplifier (Low-Z Slave Unit) - Bose FreeSpace IZA 190-HZ Service Manual

12.2 OUTPUT MONO or OUTPUT STEREO
- Place the Output Mono or Output Stereo
DIP switch on the rear panel to the Output
Stereo position. Apply a line level audio signal
to Inputs A and B on the rear panel. Verify a
stereo output from the Output 1 and 2 con-
nectors located on the rear panel.
- Remove the input signal. Change the
Output Mono / Output Stereo switch to the
Output Mono position. Re-apply the line level
signal to inputs A and B. Verify that the inputs
are now summed internally by the amplifier.
12.3 FRONT MIC MIX or FRNT MIC DUCK
- Place the Front Mic Mix / Frnt Mic Duck
switch to the Front Mic Mix position. Apply a
line level audio signal to the Input A conn-
ector on the rear panel. Apply a 1kHz,
-50dBv +/- 3dBv to the Mic/LIne input. Verify
that the Mic/Line audio input is mixed with
the audio applied to Input A.
- Place the Front Mic Mix / Frnt Mic Duck
switch to the Frnt Mic Duck position. Apply
a line level audio signal to the Input A connec-
tor on the rear panel. Apply a 1kHz, -50dBv
+/- 3dBv to the Mic/LIne input. Verify that the
Mic/Line audio input causes the Input A
audion to be muted, and that it ramps back
up and returns when the Mic/Line audio input
is removed.
12.4 AUX OUT EQ or AUX OUT FLAT
- Place the Aux Out EQ / Aux Out Flat switch
to the Aux Out EQ position. Apply an audio
signal to the Input A or B input. Verify that the
output signal from the Aux Out connector
mirrors the EQ selected for the main output.
Switch for aux out EQ mirror main output
EQ or flat EQ
TEST PROCEDURES
108

ZA 250-LZ Amplifier (Low-Z Slave Unit)

Items required:
Audio Precision ATS-1 or similar
Audio Precision AUX-0025 filter
4 Ohm, 100 Watt load resistor
Control settings:
•
Set the Output gain trim to max unless
otherwise specified.
• OUTPUT MODE: set to STEREO
• Connect the 4 ohm load to the output.
Note: All power amplifier measurements
require the Audio Precision AUX-0025 filter
to ensure correct readings.
1. Input Sensitivity Test
1.1 On the rear panel, apply a 1kHz, 0dBv
+/- 1dBv sine wave to the Input A and Input B
RCA input jacks. Verify a 50W output level
on outputs 1 and 2.
1.2 Remove the input signal. On the rear
panel, change the OUTPUT MODE switch
from STEREO to MONO. Apply a 1kHz, -
6dBv +/- 1dBv sine wave to the Input 1 jack.
Verify a 50W output level on output 1.
Repeat this step for Input 2 and Output 2.
2. THD+N Test
2.1 On the rear panel, set the OUTPUT
MODE switch to STEREO. Apply a 1kHz,
0dBv +/- 1dBv sine wave to the input RCA
input jacks. Verify a 50W output level on
outputs 1 and 2. Measure the THD+N level
at outputs 1 and 2. Verify that it is < 0.8%.
Optimum level is 0.5%.
3. Frequency Response Test
3.1 On the rear panel, apply a 1kHz, -20dBv
+/- 1dBv sine wave to the RCA input jacks.
Adjust the input signal level to obtain a 1W
output level on outputs 1 and 2. Reference a
dB meter to this output level.