Lexicon LEXICON480LV4 Owner's Manual page 93

ATC (Attack Time Constant)
ATC adjusts the speed with which the compressor
responds to an increase in input level. The nominal
value is about 30ms. The times on the slider move in
factors of 2, from 7ms to about 1 second. Both 7ms and
15ms will cause some distortion and are not recom-
mended unless delay through the program cannot be
tolerated. High values of ATC can be used with large
delays in a program-leveling application. The filter
used for ATC is a non-linear filter. The number of dB/
second depends on the rate at which the input is
changing. Fast changes will make a quicker attack,
causing the gain to decrease quickly.
RTC (Release Time Constant)
RTC adjusts the release time constant. This filter
maintains a constant number of dBs per second, re-
gardless of the size of the change. Thus, the rate of
increase in gain is constant. The value displayed for the
release time is something of an approximation, since
the ordinary meaning of "time constant" does not apply
to this type of control.
Page Two
EXS (Expand Slope)
EXS adjusts the slope of the expansion. It behaves
similarly to the compression ratio, but it is important to
keep in mind that the expander and the compressor in
this program are not in series. They both respond to the
same input level, but in different ways. For example, if
some material is compressed with a 2:1 ratio, re-
corded, and then played back through the expander
with a 2:1 expansion ratio, the original dynamics will be
restored. The same will occur if two compressor pro-
grams are run in cascade. However, if the compressor
and expander are both set to operate in the same
program at the same time with identical THR points and
slopes, the result will not' have the original dynamics.
Consider a drop in input level of 6dB. For a 2:1
compression in level the output gain should increase
3dB, giving a net drop in output level of 3dB. However,
for a 2:1 expansion, the output gain should drop 6dB,
giving a net output of -12dB. If both the compressor and
expander are operated at the same time, the net result
will be an output gain decrease of 3dB, representing a
net expansion of the signal.
Bank 10: the Compressor Programs
EXT (Expander Threshold)
EXT sets the level below which expansion starts. When
the expansion is intended to apply to the whole pro-
gram, or perhaps just to the peaks of the program, EXT
should be set to about 10 or 12dB, similar to the setting
of the THR control of the compressor. If the expander
is to be used as a noise gate, EXT should be set much
higher, to just below the level of the noise.
EXM (Expand Maximum Attenuation)
EXM sets the maximum attenuation reached by the
expander. It is similar in operation to the GAIN control
of the expander.
Programs — BANK 10:
Compressor/Expander
1 2.00=1 COMP
DLY SLP GAIN
27.45ms 2.00=1 9dB
EXS EXG EXT
2.00=1 10dB -48dB
2 6.24=1
DLY SLP GAIN
12.56ms 6.24=1 12dB
EXS EXG EXT
1.88=1 7dB -40dB
3 18.28=1 COMP
DLY SLP GAIN
20.38ms 18.28=1 10dB
EXS EXG EXT
2.00=1 10dB -48dB
4 Transfer
DLY SLP GAIN
40.26ms 1.33=1 10dB
EXS EXG EXT
1.00=1 0dB 0dB
5 Vox Easy
DLY SLP GAIN
12.56ms 5.00=1 8dB
EXS EXG EXT
1.88=1 7dB -40dB
THR ATC RTC
21dB 15ms 91ms
THR ATC RTC
16dB 7ms 91ms
THR ATC RTC
20dB 15ms 91ms
THR ATC RTC
10dB 30ms 73ms
THR ATC RTC
15dB 7ms 73ms
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