Solidyne D 816, Руководство пользователя

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5.1.7 Phase
Staying the conditions of the previous item, connect
the generator to both microphone inputs (right and
left). Connect a digital phase meter to the channels
left and right of the program output. Load each chan-
nel with 600 ohms. Change the generator’s fre-
quency to measure the phase. The variation will be
smaller than 2 degree between 50 Hz - 15 KHz.
5.1.8 Stereo Tracking
Maintain the conditions of the previous item. Change
the generator frequency to 1 kHz. Take the main fa-
der to the maximum. Adjust the Pan-Pot to obtain the
same level in both channels (L & R) of PGM output.
This level will be in order of +10 dBm. Now, move the
fader between 0 and -30 dB and measure the diffe-
rence among the levels of both program outputs.
This difference will be below +/- 0.2 dB.
5.1.9 Harmonic Distortion (THD)
Connect the audio generator at 1 KHz / 4dBm, to a
left line input. Connect a Harmonic Distortion meter
and the oscilloscope to the left program output. Load
this output with 600 Ohms. Then, select BAL and
PGM in this channel. The other switches should be
out.
Take the fader to the maximum level (0 dB). Then,
change the preset line level until obt4 dBm
on the left output. Measure now the total harmonic
distortion. Change the frequency between 30 and
15,000 Hz and to check if the distortion is below the
specification. Repeat for right channel.
Reduce now the level from the generator to -50 dBm
and connect it to the microphone input. Take the fa-
der to 0 dB position. Select MIC; change the level
from the MIC preset gain, until obt 4 dBm at
the output and to proceed like in the previous item.
It is necessary to keep in mind so that this measurement has vali-
dity, the following conditions must be verified:
1. The measurement chain must have a distortion smaller than
0,002%.
2. The distortion components, just as they are seen at the oscillos-
cope screen, connected to the output of the THD meter, must be
clearly distinguished from the residual noise and buzz.
5.1.10 Equivalent Input Noise
Connect the audio generator to a microphone input.
Load it with 600 ohms. Connect to PGM output an
audio level meter with A-weighting noise filter. Chan-
ge the generator output to 1 kHz / -50 dBm. Select
MIC and PGM in the channel under test. Enable the
module by pressing AIR. Set the main fader to -10
dB. Change the gain control until obt15 dBm
at the console output (this is the reference level:
REF). Verify that the signal does not clip.
Replace now the audio generator by a resistance of
150 ohms placed inside the connector. Measure the
residual noise in the audio level meter with “A-weigh-
ting” filter. We will denominate it Vn (dBm). Verify in
the oscilloscope that there is not any buzz; only ran-
dom noise signal. In order to eliminate buzz, recon-
nect the grounds of the measurement instruments so
that the buzz disappears. The level of equivalent in-
put noise will be:
EIN = Vgen + Vn-RE; that is to say:
EIN (dBm) = 65 + Vn(dBm)

If the “ A” weighted filter is not available, a simple RC filter
will be used, that attenuates 3 dB in 15 khz. The measured
noise will be between 5 and 7 dB above to the real one.
5.1.11 Signal/Noise ratio
In the same outline of the previous point, connect the
audio generator at 1 kHz / + 4 dBm to the line input.
Connect to the output an audio level meter with “A”
weighting filter and an oscilloscope. Load the output
with 600 ohms.
Move the fader to -10dB position. Adjust the line level
preset until get + 4dBm output and use this value as
reference for the measurement of noise. Replace the
generator by a resistor of 600 ohms and measure the
new output level. This value plus + 4dBm is the S/N
ratio.

This measurement result is the noise level in dBA.
5.1.12 Crosstalk
Connect the audio generator (+4 dBm; 1kHz), to an
left channel of a line input. Connect an audio level
meter with “A” weighting filter, an oscilloscope and a
load of 600 ohms to the left
REC output. Connect
another load of 600 ohms to the left PGM output. All
buses in others modules must be on REC bus. Move
the fader to the maximum. Change the level of the
generator until obt15dBm in the REC output.
Change the position of the audio level meter from
REC to PGM output. Verify that the audio level is +15
dBm +/- 0,5 dB.
Change the switch PGM to REC
and measure the residual level of the signal. This le-
vel, referred to +15 dBm, is the crosstalk between left
recording and left program. Repeat for all the combi-
nations of left and right program with left and right re-
cording. In the same way, the crosstalk on PGM bus
can be measured. Check it with the console specifi-
cations.
Page 28 D·816 broadcast console SOLIDYNE