Instruction manual

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14
COMPOSITE
PROCESSING
In the fully-counterclockwise (OUT) position, an
output “safety” clipper catches only those very fast
peaks and overshoots which sneak by the earlier
protection circuitry. As the COMPOSITE
PROCESSING control is rotated clockwise, the level
applied to the safety clipper is increased by the dB
value indicated on the front panel. Composite clipping
will increase apparent loudness, but at the expense of
generating some spurious harmonic products. The
following tabulation is approximate.
COMPOSITE
PROCESSING
PEAK VALUE OF
CLIPPING PRODUCTS
OUT >60dB below 100%
1dB 50dB below 100%
2dB 45dB below 100%
3dB 40dB below 100%
Composite clipping is performed prior to 19kHz stereo
pilot insertion. This averts clipping or other pilot
amplitude modulation. Nevertheless, crosstalk of the
program audio into RDS or SCA subcarriers is
exacerbated by composite clipping and its inevitable
intermodulation and harmonic generation. Use this
feature sparingly!
COMPOSITE
OUTPUT / PILOT / SUB
The PILOT INJ. and SUB INJ. controls set the injection
levels of the 19kHz stereo pilot and an externally-
applied SCA or RDS subcarrier. The OUTPUT LEVEL
control varies the overall composite output level of the
DAVID-II delivered to the exciter or STL. OUTPUT
LEVEL is a “master” adjustment and does not affect
the relationships (level ratios) between the stereo
program, pilot and RDS/SCA subcarrier.
AUDIO PROCESSING
In the IN position, this switch routes the input audio
program signal through the AGC and compressor/
limiter processing circuitry. When AUDIO
PROCESSING is switched OUT, program audio
completely bypasses the processing section. The green
LED indicates normal operation, the red LED shows
that processing has been manually defeated.
The OUT position defeats program audio pre-emphasis
as well. However, “Bass-Enhance” equalization (if
enabled), low-pass filtering (and its overshoot
correction), and composite processing do remain active
in the program signal path. It is important to leave
the AUDIO PROCESSING switch in the IN position