dbx 165A Gebrauchsanweisung - Seite 9
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OPE
RATION
&
APPLICAT IONS
Addi
tion al Inform ation on th
e
Setting and
Functi on of Certain Contro ls.
Compress
ion
Co
ntrol
T
his contro
l
is
contin uously adjustable from a com-
pression
ratio of 1:
1
to
infinite
compression (that is, no
change in
output
level
regardless
of
changes
in
input
level
above the set threshold). High compression (settings
greater than
6)
significantly
level out program
mat
erials.
Infinite compression virtually stops music levels from
exceeding
the thresho ld setti
ng.
Lower compression
settings
(below 4)
sti
ll permit dynamic range to
exi
st.
They
are
used to
t
ighten up the sound of a bass guitar,
lead guitar, snare
drum, kick drum and vocals. Moderate
overall compression
is typically used during stereo
mixdowns.
Here
a
variety of settings could be used.
While
any
compression ratio can be set with this
control,
remember that the Over Easy curve causes
that
ratio
to
be
approached
gradual
ly as
t
he
i
nput
signal
level
rises through the
threshold
.
Only when the
input
signal is considerab ly above the t hreshold does the
165
closely
approach
the set
ratio
of compression.
(See
Figure 3.)
Thr eshold Adju stm ent
&
LED Indicator
s
The Threshold contro
l
sets
the
level at whic
h
the
165
begins
to compress the
signal
(i.e., it sets the point
where
the Over Easy compression curve
intersec
t
s the
in
put signal).
The contro
l
has a wide range so that the
desired
results can be
obta
ined with any l ine
level
input
signal.
When the Threshold contro
l
is set
too
low, the
165 wi
ll compress
most if not
all
of the input
signal
(red LED ON most of the time). At low compression
ratios, the very low
threshold sett ing can be used to
gently
reduce the
overall
dynamic range of the program.
Low
threshold settings
(-
20 to
-4
0
) are used w hen
program
materia ls
are to be compressed
.
Low settings,
with
high input levels, cause
the
165 to "work"
all
or
more of
the time than with lower
input
levels.
Th
e
major
portion of program mater
ial
is processed with a
low
threshold setting.
Normal compress ion and "leveling"
of vocals
and
instruments typical
ly use lowe
r
settings.
Compression
of the whole program, however, may not
sound
natural, especially
at compression
ratios of 1
O:
1
or
greater. High
threshold
settings (-10
to +10)
are
used for limiting program
levels or where only peaks are
to be compressed.
The major portion of the program
material is
not
processed with
a high threshold setting.
Speaker
protection and
peak
overload prevention are
just two applications.
NOTE:
Whenever threshold level and compression ratio
settings
are
made,
it
is
important to watch the LED's
and meter for reference
and
confirmation.
Remember
that a compressor/limiter is a
tool
that can provide
desirable effects
when used properly. When used to
excess,
the
results can
sound unusual, and may be of
value
only for
special effects.
With the Compression
contro
l
set for
t
he desired
rnaximum
compression ratio (or an
approx imation
thereof),
rotate
the
Thresho
ld control counte
rclockwise
until
the
desired sound,
special
effect,
or
amount
of gain
reduction
is
achieved.
Auto
Switch &
A uto A
tt
ack/
Release LED Indicator
When the Auto switch is
IN (Auto Mode), the LED
indicator
will be illuminated and the
Model 165 w il
l
automatically adjust its attack rate
and
release
time to
suit the program envelope. (This
Auto Model
sets the
Model
165
for the
same
attack and
release characteristics
as dbx Models
160, 161, 162, 163 and 164 compressor/
8
li
miters .) When the Auto switch is OUT (manual mode),
t he
L
ED
indicator
above it turns OF F, and t he front
panel Attack and Release rate controls determine the
max
imum rate of
gain
change and the behavior
of
the
level
det
ector ci rcuitry (see below)
.
Attack Rate
&
Release Rate Controls
The Model 16
5
is
t
he fir st
d bx
compressor/ lim iter to
offer a choice of aut omatic or
user
adjustab le attack and
rel
ease character istics. In
A ut
o Mode, the
165
ut
il
izes
the patented dbx RMS level detector with
its
program
dependent attack/release characte rist ics
t
o obta in
natural-soundi ng co mpression or
l
imit ing. For
special
effects and certain
signal
situations, however, it is often
desi
rable to set
fix
ed attack and release characteristics.
Manual mode affords
t
h is capability. The Auto Mode is
recomme nded for vocals as wel
l
as
instrume
nts.
When
determining separate attac
k
and release rate control
settings,
it
prov ides a
good
starting poin
t
. Because the
Auto Mode has a variable
at
tac
k
rate, the
165
may
compress or limit some program mater ials smoother
than
in
t he
manu.al
mode which has a fi
x
ed rate of
attack. Th is is especially
t
rue on voca
ls.
Where To Set Attack
&
Release
Controls
There is no "right"
way
to set the Attack and
Release contro ls. Generally, one wou ld want a slow
enough Release to avoid "pumping"
or "breath ing"
sounds caused when background sounds are audib ly
mod
ulated by the dominant
signal
energy, yet t he
release must be
fast enough
to avoid supp ression of t he
desired
signal
after a sudden t
ransient
or a loud note has
decayed.
Dependin
g on t he desired
eff
ect, one might
want a very slow Attac
k
so that percussive or transient
sounds are not restricted, but average volume levels are
held w ithin the desired range.
A very fast attack setting (control
max
imum counter-
cloc kwise) w
ill
cause the 165 to act like a peak
li
mite
r
even
t hough RMS detection circuitry
is
used.
Slower
attack settings cause the 165
to
act
l
ike an RMS or
averaging detecting compressor/limiter.
Don
't
forget,
attac
k
and release co ntro ls operate toget
her
and wit
h
the compress ion ratio contro
l.
Changing any one contro
l
may necessitate changing the other sett ings.
Meter Calibration
&
Use
The meter in the 16
5
is factory calibra
t
ed to
indicate
" O" when
t
he
signal
level is
+4
d
B
(1.23 V)
at either the input or outpu
t of
the 165, depending
on the meter funct ion switc
h
posit ion.
(When
the
meter is in Gain Change mode, " O" ind icates no gain
change;
the
meter
cali
bration contro
l
does not affect
this mode.)
To
recalibrate
the meter, engage the Input meter
f unction switch and feed a
1
kHz
signal
at the selected
nom inal operating
level
(the level desired
f
or a "O
VU
"
meter ind icatio n) to the 165's
signal
input. Then adjust
the rear panel METER CAL
IBRATIO
N cont rol unt
il
the
meter ind icates "O d B".
Use of an Equalizer in th
e
Level
Detector Circu it for
Frequency Weighted Compression, De-essi
n
g,
or
Increasing Sustain
It is possible to "separate" certai
n inst
ruments from
a mix by frequency weighted compressio n.
T
his
f
unction
is created by
insert
ing an
equal
izer ahead
of t he Mode
l
165's
level
detector
input,
but not
in
the main signal
in put
path. Peaking the
equali
zer in a certain freq
uency
range wil
l
tend to supp ress any freq uencies (no
t
es)
in
that register. A relatively high th reshold setting can
allow normal sounds to be
unaf
fected whi
le
solo or very