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FIG.2 Pilot Phase 10X
e) Change the phase calibration jumper to NORMAL
mode ("N" position).
7.2.4
CHANNEL SEPARATION
Due to the high channel separation of the Solidyne
SC-100, the only way to recalibrate to original spe-
cifications is to use as reference a good measure-
ment set like the BELAR (USA) model FMS-2.
If you do not have an excellent measurement set,
please do not intend this calibration. Anyway the
Factory Calibration of our stereo coder, do not
change with the years.
Note 1:
Previous to this adjustment, the Pilot Phase (item # 2)
must be adjusted.
Note 2:
This calibration must be done with stereo coder inputs
disconnected from audio processor. Then, it must be necessary
to install a new flat cable connector set, which avoids connec-
tion with audio processor and allows direct connection of the au-
dio generator to JS1 and JS3 (JS connector).
a)
Verify that the input stage bias is correct. Use a DC
millivoltimeter to check that voltage difference betwe-
en TP2 (R222) and TP3 (R233) is less than 0,1 mV.
If not, correct it using P1.
b) Connect the BELAR measurement set to the MPX
output connector.
c) Check the PHASE mode of the Belar. You must get
at least – 65 dB rejection at 19 KHz pilot tone. If not,
please make the Belar calibration procedure of PHA-
SE (see Belar manual).
d)
Connect a sine wave generator at 400 Hz, 1V RMS
to the Left Input (pin JS1). Leave disconnected the
right input S3.
e)
Measure channel separation at the Belar. Right chan-
nel will be under 70 dB (typical is 75 dB). Correct the
phase control of the Belar to improve this figure. Cali-
brate channel separation to the minimum Right level,
using C1 trimmer at the low pass filter of SC100.
More than 70 dB rejection is a correct figure. If not,
make the complete procedure of channel separation
calibration of the Belar set (see Belar manual).
Página 44
f)
Now, connect the sine wave generator, at the same
frequency and level, to the Right Channel (pin JS3).
g)
Measure at the Belar the residual level of the Left
channel. Calibrate channel separation to the mini-
mum Left level, using P2 control. More than 70 dB
rejection is a correct figure.
h) Verify channel separation at the 20 Hz – 15.000 Hz
range. This must be better than 60 dB (65 dB typi-
cal).
7.2.5
MEASUREMENT OF RESIDUAL NOISE
Disconnect S1 and S3 from the Audio Processor.
Use a good Audio Voltmeter with A weighted filter
connected at the Left and Right audio outputs of
the BELAR modulation monitor. Use as reference 4
Vpp sine wave. Values better than 92 dBA must be
measured (94 dBA is typical value)
7.2.6
AUDIO DISTORTION MEASUREMENTS
Connect a good distortion measurement set like
System ONE, Agilent 8903B or Sound Tech ST
1710A to the Left & Right audio outputs of the BE-
LAR set. Values under 0,01 % must be measured
at 1 kHz.
Since Belar has it distortion floor at 0,01%, in order
to measure the real distortion of SC100 stereo co-
der, is recommended to use a procedure not based
on modulation monitors. Proceed this way:
a)
Connect to ground Test Point TP1 in order to cancel
19 KHz Pilot
b)
Then, connect a very low distortion audio generator
at both inputs S1 & S3. This will cancel 38 Khz sub-
carrier. Connect a good THD distortion measurement
set at the MPX output of stereo coder. Adjust to mini-
mum value the THD meter.
c) Use the monitor output of the THD measurement set
to analyze the distortion products in order to separate
38 KHz residual and noise from the true distortion
components. Use a Tektronix 5L4 N analyzer, or Tie-
Pie FFT HS3 probe, or SoundTech Lab software, etc.
Identify the harmonics of 1 KHz and calculate:
100
=
×
Distorsión
H
1
H1 = Level of fundamental tone.
Hn = Level of harmonics (reduced by the gain set
of the THD meter).
d)
Verify that the distortion level is lower than 0,003 %
at 1 KHz.
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