Za 190-Hz Amplifier (Hi-Z Slave Unit) - Bose FreeSpace IZA 190-HZ Service Manual

- Change the input signal frequency to 60Hz.
Verify that the output level is now -1dBr
+/- 1dBr.
- Change the input signal frequency to
18kHz. Verify that the output level is now
-1dBr +/- 1dBr.
4. Signal to Noise Ratio Test
Note: A 20kHz filter and A-weighting must be
used for this test.
4.1 On the rear panel, apply a 1kHz, 0dBv
+/- 1dBv sine wave to the RCA input jacks.
Verify a 50W output level on outputs 1 and 2.
Measure the signal-to-noise levels on outputs
1 and 2. Verify that they are > 88dB. Ideal is
92dB.
5. Channel Separation Test
Note: A 20kHz filter and A-weighting must be
used for this test.
5.1 On the rear panel, apply a 1kHz, -20dBv
+/- 2dBv sine wave to the Input A RCA input
jack. Increase the input signal level until you
see a 10W output level at the Output 1
connector. Measure the output level at the
Output 2 connector. It should be -55dB,
+5dB max.
- Change the input frequency to 100Hz.
Measure the output level at the Output 2
connector. It should be -65dB,
+5dB max.
- Change the input frequency to 10kHz.
Measure the output level at the Output 2
connector. It should be -50dB,
+5dB max.
TEST PROCEDURES
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ZA 190-HZ Amplifier (Hi-Z Slave Unit)

Items required:
Audio Precision ATS-1 or similar
Audio Precision AUX-0025 filter
50 Ohm, 100 Watt load resistor
100 Ohm, 100 Watt load resistor
Note: All power amplifier measurements
require the Audio Precision AUX-0025 filter
to ensure correct readings.
Control settings:
• Set the Output gain trim to max.
• Connect the 50 ohm load to the output
for 70V output units. Connect the 100
ohm load for 100V output units.
1. Input Sensitivity Test
1.1 On the rear panel, apply a 1kHz, 0dBv
+/- 1dBV sine wave to either the left or
right RCA input jack. Verify a 90W output
level on the output connector.
2. THD+N Test
2.1 On the rear panel, apply a 1kHz, 0dBv
+/- 1dBv sine wave to either the left or right
RCA input jack. Verify a 90W output level on
the output connector. Measure the THD+N
level at the output connector. Verify that the
level is < 0.8%. Optimum level is 0.5%.
3. Frequency Response Test
3.1 On the rear panel, apply a 1kHz, -20dBv
+/- 2dBv sine wave to the RCA input jacks.
Adjust the input signal level to obtain a 1W
output level on at the output connector.
Reference a dB meter to this level.
- Change the input signal frequency to 60Hz.
Verify that the output level is now -4dBr
+/- 1dBr.
- Change the input signal frequency to
18kHz. Verify that the output level is now
-1dBr +/- 1dBr.