Mackie HR824, Руководство по обслуживанию

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16
LOW FREQUENCY AMPLIFIER TESTS
ACOUSTIC SPACE SWITCH
Disable the compressor circuit by shorting together pins 1 and 2 of J12.
Turn off the amplifier and connect the two resistor loads as shown on the previous page.
Set all switches to the NORMAL position and turn on the amplifier.
Set your audio signal generator for an output of 300mVrms(-10.46dBV).
Measure the output into the 4 ohm load for the three positions of the ACOUSTIC SPACE switch.
Do these measurements fairly quickly because the amplifier will be warming up.
The level of the output may be different from that shown, due to the factory settings of the
calibration pots. Just make sure that the speaker under test follows the overall shape and the
switch is working.
THD
Measure the THD at 400 Hz and verify it is less than 0.1%
FREQ(Hz)
100 200 300 500 1k 2k 30 50
LOW FREQUENCY AMPLIFIER OUTPUT
15
10
5
1
20
15
10
5
1
20
0.0
5
10
15
20
25
30
AMPL(dBV)
0.0
5
10
15
20
25
30
AMPL(dBV)
Vrms Vrms
ACOUSTIC SPACE
(Vary during this test)
LOW FREQ
(keep on 37Hz)