Omnia Omnia-3

52
Clip (Omnia-3am and Omnia-3fm Turbo only)
Drive: Here is where the loudness versus quality trade-off is most evident. Generally you want to set this
control to the lowest value possible to achieve the desired loudness level. A good strategy is to reduce it in 0.5
dB steps until loudness falls off perceptibly and then increase it one step. Adjustment is in 0.1 dB steps, so
making minor changes will not create an abrupt overall change to the signal. Be careful with this one; there is a
lot of available power here!
P.A.C : (Omnia-3fm Turbo only) Set this to ON only when using an AES / EBU digital output connection from
the Omnia-3 to a digital FM exciter.
This Prediction Analysis Clipper (P.A.C.) mode compensates for overshoots that invariably result when an
AES/EBU interconnection, involving multiple stages of sample rate conversion and lowpass filtering, is used.
Under these conditions:
• Overshoots occur whenever down-conversion of a 44.1 or 48 kHz sample rate to 32 kHz sampling is
performed
• The tight transition slope of the 16 kHz filter in the sample rate converter is a significant contributor to
overshoots
• The problem occurs only with signal components above 5 kHz.
Yet:
•
We do not want to reduce the slope of the lowpass filter in the audio processor, as it degrades sound
quality.
• Adding more clippers and filters only increases distortion.
Fortunately, it’s possible to pre-compensate for predicted occurrences of overshoots by the use of
supplementary control signals. These are applied to the upper audio spectrum by the Omnia-3’s main clipper
algorithm—the same one employed to eliminate digital grunge!
As a practical matter, the use of the Prediction Analysis Clipper reduces overshoots in the sample rate converted
signal path from a worst case of 20% to less than 3%.
Final Limit (Omnia-3net/drm only)
This is the final limiter that operates in place of the clipper on all of the other Omnia-3 styles. There are two
controls here: With the first you can turn the final limiter ON or OFF. This should normally be left ON unless
the equipment following the Omnia-3net/drm has a non-defeatable limiter or otherwise requires non-limited
audio.
The second is the Drive control, which controls the amount of final limiting. The gain-reduction of the final
limiter can be monitored on the Process Bargraph screen.
Comp (Omnia-3fm Turbo only)
The Drive setting in this block controls the drive to the DSP-based composite clipper. A setting of 0.0 is the
same as the clipper being “off “. This clipper operates on the entire baseband signal up to 53kHz, except for the
19kHz pilot. No matter how hard you drive the composite clipper, you cannot clip the stereo pilot. Embedded
within the composite clipper is a 53Khz phase linear low pass filter for SCA protection.