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TASCAM TA-1VP 11
Limiting
Examine the 99:1 curve in the above graph. This setting
reduces all sounds above the threshold to the same
loudness. This is called limiting. Limiting is usually
employed to allow a dynamic signal to be recorded at a
maximum level with no risk that transient peaks will result
in overload. In this application, the threshold setting
(usually set relatively high) determines the extent to
which the peaks will be limited.
Dynamic Expansion and Gating
Sometimes, it is desirable to increase the difference
between the quietest signal and the noise in a recording
by using a downward expander. A typical application
would be eliminating room noises and breath sounds that
can be heard between the phrases of a recorded vocal
part.
The graph below shows the curveÉ<or a downward
expander. Notice that above the threshold, the curve
follows a 1 to 1 ratio (i.e., is unaffected by the gate). For
each unit of input change below the threshold the output
changes by two units. This is called a 1 to 2 expansion
ratio.
As the input signal drops below the threshold, its output
level drops at twice the rate it would using a 1 to 1 ratio.
In effect, sounds below the expander threshold are “faded
out” more quickly than they would be normally.
OUTPUT
LEVEL
INPUT LEVEL
LOUDER
LOUDER
THRESHOLD
1 TO 2 EXPANSION RATIO
1 TO 1 RATIO
When expanders use ratios higher than 1:10, sounds
below the threshold are faded out very rapidly. This effect
is called gating and can sound very abrupt. Adjusting the
gate ratio can smooth out the abrupt change. The graph
below shows the input/output curve for a typical gate.
OUTPUT
LEVEL
INPUT LEVEL
LOUDER
LOUDER
THRESHOLD
1 TO 99 EXPANSION RATIO
1 TO 1 RATIO
Sounds that are louder than the threshold get “through
the gate” unchanged. Sounds that are below the
threshold are not heard. Gates can be used to great
effect in processing drum tracks where sounds from the
other instruments in the drum set leak through the mike
of the instrument being recorded. Gates are also used
frequently to “gate off” a reverb tail or the ringing from an
insufficiently damped drum head.
Compression and Expansion
Combined
The TA-1VP allows you to use both compression and
expansion simultaneously. This ability is useful in taming
the typical problems that arise when processing vocal
tracks. The graph below illustrates the use of compression
with a downward expanding gate.
OUTPUT
LEVEL
INPUT LEVEL
LOUDER
GATE THRESHOLD
COMPRESSOR THRESHOLD
1 TO 99 EXPANSION RATIO
4 TO 1 RATIO
Using this setting, levels above the compressor threshold
will be compressed at a 4 to 1 ratio. Levels below the
compressor threshold but above the gate threshold will
not be changed. Levels below the gate threshold will be
gated out completely.
2 – Introducing the TASCAM TA-1VP Vocal Producer