Yamaha SB168-ES, Руководство по обслуживанию

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SB168-ES
74
1. Preparation
1-1. Setup
Conduct the ANALOG IN/OUT characteristics test with the
ANALOG test of the test program. Set up so that the test
program can be executed referring to “Test Program” (page 46).
1-2. Measuring Instruments
Use measuring instruments which can measure the inspection
items accurately with con
fi dence.
Input impedance of the measuring instrument should be 100 k Ω
or more.
· Level meter
· Frequency counter.
· Distortion meter
· Oscillator
1-3. Parameters
Unless otherwise speci fi ed, the following conditions should be
met.
· Set 0 dBu = 0.775 Vrms.
· 0 dBFS = 0 dB, full scale
· Set the +48V MASTER switch to ON.
· Analog output load should be 600
Ω for each channel.
· Weight with LPF at 12.7 kHz, -6 dB/oct during the
measurement of noise level and crosstalk between adjacent
channels. Measuring should be at average values, not root-
mean-square values.
· Correct the distortion measurement with an 80 kHz, -18 dB/
octave low pass fi lter.
· Set the oscillator output impedance to 150 Ω .
2. ANALOG IN/OUT Characteristic Test
2-1. INPUT 1 – 8 → OUTPUT 1 – 8
Select the test program menu “MUTE OFF” for the tests
①
through
⑤
. (See page 55)
Select the test program menu “MUTE ON” for the test
⑥
.
(See page 55)
Parameters
Input an analog signal from the CHn input (n = 1 to 8) and
measure the output signal from the CHn output (n = 1 to 8).
① Gain
Input Frequency Input Level Specifi ed Output Level Permissible Range
1 kHz +10 dBu +4 dBu +4 ±2 dBu
② Distortion
Input Frequency Output Level Permissible Range
1 kHz +4 dBu 0.05% or less
1 kHz +22 dBu 0.01% or less
③ Residual noise
Parameters
Short the INPUT to be measured with 150 Ω .
Permissible Range
-80 dBu or less
④ Level Difference between channels
The range of difference in the gain measured in the item
①
should be as follows.
Permissible Range
Within 1.5 dB
⑤ Crosstalk between adjacent channels
Parameters
Measure the noise level between an odd number channel and
the adjacent even number channels on both side. Open the input
of the even channels to be measured.
Input Frequency Output level (Odd channel) Permissible range (Even channel)
1 kHz +23 dBu -57 dBu or less
The parameters for even channels are the same.
⑥
MUTE signal (OUTPUT 1)
Output a signal of +4 dBu from an output and check that output
level is -25 dBu or less when the MUTE is turned ON.
Take measurement of OUTPUT 1 as a sample.
2-2. Sound check
Select the test program menu “GAIN MIN”. (See page 55)
Input an analog signal (400 Hz, +10 dBu) from the CH1 input
and audibly check the analog signal output from the CH1
output.
Audibly check for over 15 seconds and make sure that no noise
is output.
2-3. Vari pitch sound signal test
Select the test program menu “GAIN MIN”. (See page 55)
Input an analog signal from the CH1 input and measure the
output signal from the CH1 output.
Gain
Word Clock
Input
Frequency
Input Level
Specifi ed
Output Level
Permissible
Range
q
43.0 kHz
1 kHz +10 dBu +4 dBu +4 ±2 dBu
w
49.2 kHz
Audibly check for over 15 seconds and make sure there is no
sound discontinuity or distortion.
INSPECTIONS