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3.
Power Amplifier Part
3-1 Setting Conditions
Setting conditions are as follows unless otherwise specified.
Input terminal:
POWER AMP switch:
Output terminal:
Output Load:
INPUT CH1 - 4, CH6
LEVEL control:
3-2 Power ON Muting
The muting relay should be released 2.5 +/- 1 seconds after the power switch is turned on.
3-3 Speaker Terminal DC Voltage
When input terminals are grounded, confirm that each output terminal voltage is 0 +/- 100 mV.
3-4 Gain
Check that +22 ± 2.0dBs output voltage is obtained when a -26dBs signal is input to the input terminal. Perform
the same check under the setting conditions of POWER AMP switch at MAIN-MAIN and the output terminals at
POWER AMP 1G and POWER AMP 2B.
3-5 Frequency Response
Apply a -26dBs signal to the input terminal and check that the output voltage when the signal frequency is 20Hz
and 20kHz is within +1 and -3dB ranges respectively, using the output voltage at 1kHz as reference.
3-6 Harmonic Distortion
Apply a 1 kHz sine wave signal to the input; the output level should be 300 W/4 ohms (33.0 dBs/ch); the distortion
ratio should be less than 0.5 %.
Apply a sine wave signal of 20 Hz, 1 kHz and 20 kHz separately to the input; the output level should be 150 W/4 ohms
(30.0 dBs); the distortion ratio should be less than 0.5 %.
Do this inspection within 30 seconds.
3-7 Residual Noise
Set the MASTER level controls (MONITOR and MAIN) at minimum; the residual noise at the output terminal should be
less than -65 dBs.
Note: Use DIN-AUDIO filter.
3-8 Stability
Apply a 10 kHz -26 dBs rectangular signal to the input and connect a capacitor (10 pF to 0.47 µF) parallel to the 4
ohm load resistor, or connect an inductor (10 µH to 0.47 H) serial to the 4 ohms load resistor. Confirm that the output
signal is as illustrated below.
Overshoot:
Vp/Vo 1.8
Ringing:
5 waves and less than 5 waves
Next, only connect a capacitor (10 pF to 0.47µF) to the SPEAKERS terminal as a load, and confirm that the output
is as follows:
Overshoot:
Vp/Vo 2.5
Ringing:
It should end within 7 waves; there is no oscillation.
INPUT CH5 LINE1
MAIN-MONITOR
POWER AMP 1A, POWER AMP 2A
4 ohm (more than 300W)
Connect the load resistor of SPEAKER OUT only when inspecting the
power amplifier section unless otherwise specified.
Minimum
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Vp
Vo
EMX660
21
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