Lighting Check Of Level Meters; Distortion; Maximum Output; Equivalent Input Noise - Yamaha MG 166CX-USB Service Manual

MG166CX-USB/MG166CX/MG166C-USB/MG166C

2-12 Lighting Check of LEVEL meters

Check the "0" indicator of meter lights up when the output level at ST OUT (L, R) is +4 ± 2 dBu.
Move the ST master fader and check the indicators light up in order from "-30" to "PEAK".

2-13 Distortion

In the signal routes 3 to A specified in the table 2-6-1 to 2-6-6, set the GAIN controls to the position specified in the table
(except PHONES), and apply the frequency 20 Hz, 1 kHz and 20 kHz. Then check the distortion is 0.1 % or less, when the
output signal level obtained at the each output terminal is +14 dBu.
Also check the distortion is 0.2 % or less, when the output signal level obtained at the MONITOR OUT (L/R) is +14 dBu.
In the signal route A, turn the PAN/BAL control to L or R fully and measure the distortion when the signal level obtained at
*
ST L or R OUT is +14 dBu.
In the signal route 9, measure the distortion of all output terminals in the table 2-6-1.
*
* In the signal route 0, check the distortion is 0.1 % or less when the signal level obtained at INSERT OUT is +10 dBu.
* Set the unmeasured output master level control and fader to minimum.

2-14 Maximum Output

With controls set as specified in the section 2-2, check the distortion is 1 % or less when the output level is +24 dBu at ST OUT.
Check the distortion is 1 % or less when the output level obtained at GROUP OUT, AUX1, AUX2, AUX3 SEND (MG166C-USB,
MG166C), AUX1, AUX2, EFFECT SEND (MG166CX-USB, MG166CX) and MONITOR OUT is +20 dBu.
Check the distortion is 1 % or less when the output level obtained at PHONES (L, R) is +7.5 dBu.
Notes:
• When measuring ST OUT and GROUP OUT, turn the PAN or PAN/BAL control to the left or the right fully.
• Only when measuring PHONES, turn the PFL switch of INPUT channel to ON.

2-15 Equivalent Input Noise

With controls set as specified in the section 2-2, connect pin 2 (hot) and pin 3 (cold) of the CH INPUT MIC terminal with
150 Ω and check the noise level obtained at ST OUT L is -44 dBu or less.
If the noise level exceeds -44 dBu, check the equivalent input noise level is -128 dBu or less.
With controls set as specified in the section 2-2, connect pin 2 (hot) and pin 3 (cold) of the ST INPUT MIC terminal with 150 Ω
and check the noise level obtained at ST OUT L is -37 dBu or less.
If the noise level exceeds -37 dBu, check the equivalent input noise level is -121 dBu or less.
Notes:
• Set the LEVEL controls of input channels except measured one to minimum.
• Noise should be measured with a 12.7 kHz -6 dB/octave low pass filter.
• The equivalent input noise level is obtained by subtracting the channel gain from the noise level.
2-16 Residual Noise
With controls set as specified in the section 2-2, set the fader and LEVEL controls of all input channels to minimum and the
assign switches of all input channels to OFF.
Then check the noise level is less than the values in the table 2-16 when the fader and LEVEL controls of MASTER is set to
maximum or minimum.
Table 2-16
FADER/VR
Max.
Min.
Notes:
• When measuring MONITOR OUT, set the ST FADER to minimum.
• Noise should be measured with a 12.7 kHz -6 dB/octave low pass filter.
48
STEREO OUT GROUP OUT
(L, R) (1-4)
-78 dBu -80 dBu
-98 dBu -100 dBu
AUX1, AUX2, AUX3 SEND (MG166C-USB, MG166C)
AUX1, AUX2, EFFECT SEND (MG166CX-USB, MG166CX)
-75 dBu
-100 dBu
MONITOR OUT
(L, R)
-72 dBu
-85 dBu