dbx 128 - Page 35

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dynamic range at ali times, regardless of level. This means such matching is unnecessary (the PLAY LEVEL MATCH
that the gain changes are very gradual, spread evenly over feature is more for the benefit of ““A-B’’ comparison than
the dynamic spectrum. Non-dbx systems which concentrate anything else).
gain changes only at the upper or lower end of the dynamic The peak unlimiting capability (or peak limiting capability)
range must, necessarily, cram a lot of gain change into a of the 128 is a special purpose feature. When the 128 is in
small
area.
Obviously,
the
audio
quality
cannot
benefit
from
the
ABOVE
THRESHOLD
mode,
it
operates
by
‘ignoring’
such processing. Furthermore, the use of a threshold-type all data below the preset THRESHOLD level (set by the
system necessitates tricky compression/expansion adjust- LEVEL control). Above that level, the compression or ex-
ment
that
would
require
repeated
attention
with
almost
pansion
works
just
as
when
the
128
is
in
its
LINEAR
mode.
every new program. The linearity of the dbx system means
Fig. 19 — Compression/Expansion
.
A. Linear expansion operates over the
entire dynamic spectrum of music irrespec-
tive of frequency (20-20,000Hz), making
loud passages louder and quiet passages
quieter, reducing audible noise. Expansion
ratios are adjustable. For example: 1.0 = 0%
increase in dynamic range; 1.2 = 20%;
1.5 = 50%; 2.0 = 100%.
B. Above threshold expansion is used to
make loud passages louder above a user
adjustable threshold level when no low level
dynamic alteration is desired.
C. Linear compression reduces the
entire dynamic range of the music irrespec-
tive of frequency (20-20,000Hz).
D. Above threshold compression has no
effect on low level signals. When signal level
reaches the adjustable threshoid, the
dynamic content of the music is decreased
but only above that threshold. Higher com-
Pression ratios may be used in above thres-
hold compression than in linear compression;
however, all ratios are available.
55 4B
Program 56
, program
expanded
program at 14
program peak expanded program above threshold
program at 16 compression at 4.0
above Ihreshold