Preventing tape saturation
A
high
threshold (but below tape saturation) and high
compression
ratio will cause
the compressor to reduce gain in a controlled manner
before
the tape overloads and
distorts.
Speaker protection and acoustical
distribution
Compression will keep
excessive levels from damaging drivers in sound-reinforce-
ment systems. Limiting also enhances
intelligibility by letting low-level material be
reproduced throughout the
house
at higher volumes; in a performance, this increases
intimacy, as whispers
become
clear
at virtually every seat. Our OverEasy characteristic
permits high amounts of compression (e.g., iO:l) to be used without vocalists or musicians
feeling choked back
—
and with high average levels
maintained
without speaker damage
due to heat buiidup in the drivers. As
a
rule, to give tiie best protection, your 1 66
should
be as close as possible in the signal path to the power
amp. For maximum
SPLs, large
sound-reinforcement systems frequently
have a
separate compressor on each output of
the electronic crossover's).
Where
the 166 will be expected to allow
virtually
no
level change unless an emer-
gency (wildly excessive levels) arises, set the ratio to Infinityti and the
Threshold
to the
highest level. OverEasy will
never
act
in
the fast, unpleasant manner of a typical "hard-
knee" compressor, but it will give a measure of real protection. See the
next
section,
too.
ABOUT LIMITING and SOFT CLIPPING
PeakStop
ediows you to
control
the
maximum peak levels at the output of the
1 66
irrespective
of
any other control.
As
mentioned, it
comes after the compression and
other circuitry,
including
the output gain, so
it lets an absolute limit be put on the peak-
to^>eak excursions
of
the output. PeakStop works instantaneously; you'll be able to apply
moderate amounts of compression
and still be
independently protected from
large trans-
ients, other
short-term
overloads,
and broadcast overmodulation.
PeakStop
cwsists of
a
sophisticated voltage-controlled clipper that produces a
minimum
of
audible
distortion. It rounds the comers of a peak rather than cutting it off
sharply, as the term "clipping" implies.
By
making a signal's
leading
and trailing edges
curves instead
of
sharp corners,
it reduces the
amount
of
higher-order,
offensive-sounding
harmonics that conventional clipping causes. The level at which PeakStop is activated is
adjustable from 0 to
+20 dBv. Note
that small signal excursions above the s^ value of
PeakStop are possible, to allow the rounding to take place. Therefore, for any applica-
tions where you
must not exceed
a
given ceiling, set the PeakStop
control
1-2
dB
below
it
to be sure.
The PeakStop LED flashes whenever peaks attempt to exceed the PeakStop level
and
get reduced
in
amplitude. To disable
the
function
altogether, simply set the control
to +20 (which is the maximum output level of the 166 anyway).
In
use, the
PeakStop function can prevent
an
amplifier from
being driven into hard
clipping, where it may lose control over the speaker
system.
PeakStop Is a smooth, well-
controlled clipper whose behavior is s<micaiiy similar to the gentleness of OverEasy com-
pression; its clipping is much
preferable
to a
power
amp's.
As
noted, control of speaker
overexcursion, of broadcast overmodulation, and
of
harsh electronics clipping are all
applications; with PeakStop and OverEcisy, you have the best of both worlds: virtually
inaudible
rms compression and peak protection downstream,
at the end.
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9
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