Cross talk: Set the Function Reading to Cross-talk. With channel A selected for
measurement, remove the source signal from channel A. The resulting
measurement is an indication of how much of the signal from channel B is
affecting channel A. Restore the source to channel A and perform the same
test on channel B.
Frequency Response: With both generators active, and with the Bandwidth set
to maximum (<10Hz and >500kHz), the frequency response of the unit can
be plotted. Set the DPS-475 headroom back to its nominal value of 18dB.
Set the generator output levels to 17.5dBu. Set dBr A and B values to their
respective readings. Invoke the Audio Precision Sweep table. Set Data 1 and
Data 2 to “Anlr Level” A and B respectively. Set the top and bottom limits
for both channels to +0.5dBr and –0.5dBr A or B as appropriate. Set Source
1 to “Gen.Freq”, with a start of 20Hz and a stop of 20kHz, for a total of 200
steps. Press the “go” button. The sweep will take several seconds to
complete. Evaluate the graph to determine if the measurement is within
specifications.
Measurement Maximum Minimum
Phase +0.2° -0.2°
THD+N – Non weighted 0.005%
THD+N – A-weighting 0.005%
Full Scale Output (THD+N < 0.01%) 23.1dBu
Signal to Noise Ratio – A-weighted -71dB
Channel Separation (Cross-talk) +0.005% -0.005%
Frequency Response 20Hz ~ 50Hz +0.2dB -0.2dB
Frequency Response 50Hz ~ 15kHz +0.05dB -0.05dB
Frequency Response 15kHz ~ 20kHz +0.5dB -0.5dB
Remaining Audio Channels
Repeat allof the above tests for the remaining two channels.
The Digital Audio Interfaces
This group of tests will ensure that the digital interface of the audio card is
functioning correctly and within specifications. For all of these tests, the basic
parameters of the DPS-475 Test Bench Unit should be modified as follows, unless
otherwise indicated:
Parameter Channel 1 Channel 2
Input AES AES
AES/EBU Process Process
Test Tone Freq. L 1000Hz 3000Hz
Test Tone Freq. R 2000Hz 4000Hz
116
DPS-475/575 Service Manual
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