Table of Contents
Advertisement
3.4.2
EFFECTS
OF
COMPRESSION RATIO
A moderate form
of
gain reduction
is
achieved with ratios up
to about 8:1.
The dynamic range of the program material
is
controlled
without obvious alteration.
The average signal level will be
increased
and the
softer passages will be made louder.
A more drastic gain reduction results from compression
ratios
of 12:1 and 20:1.
The output signal level
is
limited, and for
practical purposes cannot exceed
a
preset level.
Dynamic range
is
significantly reduced,
and
high
level peaks are minimized.
3.4.3
EFFECTS
OF
THRESHOLD
Changing the relationship of the average input level
to
the threshold will
determine the amount
of
gain reduction,
or
how
much of the signal envelope
is
affected by the limiter action.
If
only occasional large-amplitude
peaks are allowed to exceed
this threshold, the
program material remains very much
the same.
However, overload problems which would be caused by these peaks are
eliminated.
The result can be
an
increase
in
loudness because the
operator can raise the signal level without adding distortion due
to
headroom limitations.
When
the input
is
adjusted so that the average signal level
is
above the threshold all the
time,
then
the entire
program material
will be compressed.
Monitoring the amount of gain reduction
is
made easy when the meter function
is
switched to
the
GR mode.
3.4.4
EFFECTS
OF
ATTACK TIME
Fast transients and high frequencies with large peak-to-peak
amplitudes can only be limited
or
compressed
if
a
fast attack time
is
chosen.
Then any overshoot,
and
with
it
overload problems,
are kept
to
a
minimum.
However, limiting with
a
fast attack time
alters the musical
quality of some instruments which are character-
ized
by sharp percussive attacks.
A slow attack time will allow the
first segment of fast
^pli-
tude changes to pass through the limiter unaffected.
The limiter
reduces gain after the initial envelope attack of the program
material.
Thus,
slow attack maintains
the "punch" of such percus-
sive instruments
as
drum, bass, piano, guitar, etc.
with some
sacrifice
of
amplitude control.
The aim of the user
in
adjusting the limiter
for the
correct
attack time then
is
to find the
best setting
for the
task at hand.
It
may be
a
compromise between
a
permissible
eimount
of initial
peak-to-peak amplitude before
full compression, and
how
much alter-
ation of the program material
is
acceptable.
-
13 -
Advertisement
Table of Contents
Troubleshooting
