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5-6
Troubleshooting
L–R (Stereo Difference Channel) Will Not Null With Monophonic Input
This problem is often caused by relative phase shifts between the left and right channels prior to the 5750's input.
This will cause innocuous linear crosstalk between the stereo main and subchannels. Such crosstalk does not cause
subjective quality problems unless it is very severe.
Audio Mute Occurs When Switching Between UL and Non-UL Presets
This is normal. It occurs because the DSP code must be reloaded.
HD Output Sounds Too Bright
Enable adjustment of the HD output's spectral balance by putting the on-air preset into INDEPENDENT mode. Do
this by setting the FM→HD CONTROL COUPLING control in the HD LIMITING page of ADVANCED CONTROL to
INDEPENDENT. You can also toggle this control via two buttons on the button bar in HTML application.
In this mode, the HD processing channel's equalizer, five-band compressor, and band-mix controls are independent
of the corresponding controls in the FM channel and can be adjusted separately. You can therefore fine-tune high
frequencies by adjusting the equalizer, parameters in the band 4 and band 5 compressors, the band 4 and band 5
BAND MIX controls, and the HD DE-ESS control. One of the most effective ways to tame harsh high frequencies
dynamically is to activate the HD channel's band 5 compressor.
Harsh Sibilance ("Ess" Sounds) in the HD Channel
Adjust the HD DE-ESS control and/or activate the HD channel's band 5 compressor.
HD and FM Levels Do Not Match When the Receiver Crossfades
Adjust the HD LIMIT DR control in the on-air preset to match levels.
Do not match levels by adjusting the output level of the output driving the HD exciter. Only use this control to match
the peak levels of the OPTIMOD output to the exciter.
In other words, if the exciter is set to clip when it receives at –3 dBFS, adjust the OPTIMOD output level to –3 dBFS.
This uses all of the headroom available in the transmission channel, minimizing the amount of look-ahead limiting
that the OPTIMOD needs to do.
If you have accidentally turned on the BS.1770 Safety Limiter, this will cause the loudness to be lower than expected
in HD Radio applications. Turn it off.
Loudness is unexpectedly low from the analog FM processing chain
The MPX Power Controller and/or analog FM processing chain BS.1770 Safety Limiter may have been turned on
accidentally.
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