Orban OPTIMOD-FM 5500 Operation Manual page 202

4-10
MAINTENANCE
DSP, the D/A converter, and the analog output circuitry.
H) Repeat steps (C) through (G) for the right channel.
5. Check distortion performance of Analog I/O.
A) Verify 5500 software controls are set to their default settings. (Refer to page
4-7.)
B) Be sure you are still in B
+17.0 dB.
C) Set the AO 100% control to +20 dBu.
D) Connect a THD analyzer to the Left Analog Output XLR connector. Set the
THD analyzer's bandwidth to 22 kHz.
E) Connect the oscillator to the Left Analog Input XLR connector. Set its fre-
quency to 50 Hz and its output level to +10 dBu. This should produce a level
of approximately +18 dBu at the 5500's output.
F) For each frequency used to measure THD, adjust the output level of the oscil-
lator to make the C
the output level of the oscillator at higher frequencies to compensate for the
pre-emphasis boost in the 5500. As the frequency increases, you will have to
reduce the output level of the generator to follow the 75s deemphasis curve.
At 15 kHz, you should have to reduce the output of the generator to ap-
proximately –7 dBu.
G) Measure the THD+N at the frequency levels listed below.
Frequency
50 Hz
100 Hz
400 Hz
1 kHz
2.5 kHz
5 kHz
7.5 kHz
10 kHz
15 kHz
H) Repeat the above measurements for the right channel. Connect the oscillator
to the right analog input and the distortion analyzer to the right analog out-
put.
I) Disconnect the oscillator and THD analyzer from the 5500.
6. Test Digital Sample Rate Converter (Receiver).
A) Verify 5500 software controls are set to their default settings. (Refer to page
4-7.)
B) Be sure you are still in B
mode [see step (3.F)] and set the B
YPASS
meter on the 5500 read 100. You will have to reduce
OMP
THD+N Typical
0.015%
0.015%
0.015%
0.015%
0.015%
0.015%
0.015%
0.015%
0.015%
mode [see step (3.F)].
YPASS
ORBAN MODEL 5500
YPASS
THD+N Maximum
0.03%
0.03%
0.03%
0.03%
0.03%
0.03%
0.03%
0.03%
0.03%
to
G
AIN