dbx 2BX Instruction Manual
db:>X
Model 2BX
two band
dynamic
range enhancer
INSTRUCTION
MANUAL
WARNING:
TO
PREVENT
FIRE
OR
SHOCK
S^
A
A?
D
vPi\
N0T
^OSE
THIS
APPLIANCE
TO
RAIN
OR
MOISTURE
dbx®
is
a
Registered
Trademark
of
dbx.
Inc.
INDEX
BRIEF
OPERATING
INSTRUCTIONS
INTRODUCTION
CONNECTIONS
OPERATION
EXPANSION
SIMPLE
PRECAUTIONS
WHEN
USING
ANY
PROGRAM
EXPANDER
HOWdbx
EXPANDERS
WORK
'
SPECIFICATIONS
"
dbx PRODUCT
WARRANTY
FACTORY
SERVICE
"
SCHEMATIC
"
'
GLOSSARY
"
BRIEF
OPERATING
INSTRUCTIONS
PILOT
This
L.E.D.
(light
emitting
diode),
above
the
POWER
switch,
glows
when
the
2BX is
ON.
GAIN
CHANGE
L.E.D.'s
These
two
rows
of
L.E.D.'s
indicate
the
amount
of
gain
change
created
in
each
of
the
2BX's two
frequency
bands.
The red
L.E.D.'s
indicate
upward
expansion
(volume
increase),
the
yellow
L.E.D.'s
indicate
downward
expansion
(volume
decrease).
TRANSITION
LEVEL
When an
incoming
signal
is
above
the
level
set
by
this
control,
the
2BX
expands
up-
wards;
when an
incoming
signal
is
below
the
level set
by
this
control,
the
2BX
expands
downward.
Set
the
control
so
that
red
GAIN
CHANGE
L.E.D.'s
glow
during
loud
portions
of
the
program
and
yellow
GAIN
CHANGE
L.E.D.'s
glow
during
the
quiet
portions
of
the
program.
SOURCE
Push
this
switch
and
the
PRE
switch to
expand
programs
coming
from
your
phono-
graph,
FM
tuner
or
other
auxiliary
equipment.
TAPE
Push
this
switch
and
the
POST
switch
to
expand
programs
coming
from
your
tape
recorder.
If
you
do
not
have
a
tape
recorder,
push
the
SOURCE
switch.
PRE Push
this
switch
to
expand a
program
before
recording
it.*
POST
Push
this
switch
and
the
TAPE
switch to
expand
a
program
played
back
from your
tape
recorder.
POWER
Push
this
switch
once (IN) to
turn
the
2BX
ON; push
again
(OUT)
for
OFF.
EXPANSION
Adjust
this
slide
control
for
the
desired
amount
of
expansion.
A
"1.4"
setting
means
that
an
input
signal
with a
40dB
dynamic
range
will
be
expanded
to
56dB,
or
that
an
input
signal
with
a
50dB
dynamic
range
will be
expanded
to
70dB.
A 1.2
setting
would
result
in a
20%
increase
in dynamics;
a
1.4
setting
would
result
in a
40%
increase
in
dynamics,
etc.
(PRE/POST
Summary)
The
PRE switch
expands
the
signal
before
the
tape
recorder
input
(PRE
places
the
expander
before
the
tape
recorder
input);
the
POST
switch
expands
the
signal
from
the
tape
recorder's
output
(POST
places
the
expander
after
the tape
recorder
output).
Pushing
both
PRE and
POST
switches
simultaneously
bypasses
the
expander
functions.
"Expansion
will,
in
most
cases,
increase
the
dynamic
range
of
a
program
beyond
the
capabilities
of
your
tape
recorder.
To
capture
this
increased
dynamic
range
on
tape
requires
a
dbx
noise
reduction
system,
which
a/lows
recording
at
levels
below
the
tape
or
tape
head's
saturation
point
To
expand
a
program
and
then
record
it,
we
recommend
using
any
dbx
tape
noise
reduction
system
and
carefully
setting
record
and
expansion
levels.
If you
do
not
have
a dbx
tape
noise
reduction
system,
we
recommend
expanding
a
program
upon
playback
(place
the
1bx in
TAPE
and
POST
mode).
RECORDER
OUTPUTS*
Connect
the
cables from
these
outputs
to
the
Line
inputs
of
your
tape
recorder.
If
you do not have
a tape
recorder,
do not connect
any
cables
to
these
outputs.
RECORDER
INPUTS*
Connect
the
cables
from
your
tape
recorder
Line
or
Monitor
outputs
to
these
inputs.
If
you do
not
have
a
tape
recorder,
do
not
connect
any
cables
to
these
inputs.
INPUTS
Connect
the
cables
from
the
Tape
Outputs
of
your
receiver,
preamplifier,
or
integrated
amplifier
to
these
inputs.
OUTPUTS
Connect
the
cables
from
these
outputs
to the
Tape
Inputs,
or
Monitor
Inputs
of
your
receiver,
pre-
amplifier,
or
integrated
amplifier.
AC
POWER
CABLE
In
the
U.S.A.
connect
this
cable
to
a
1 1
7V
AC,
50
or
60Hz
AC
power source.
The
2BX
requires
a maximum
of
20 watts
of
AC
power.
Models
for
use
with
power
sources
outside
the
United
States
are
available.
Contact the
dbx factory
for
information.
*/f
you have
a
dbx tape
noise
reduction
system
(such
as any
of
our
120 or
150
series)
see
Page
9
for
connection
diagrams.
INTRODUCTION
If
you're
a
music
lover
or
an
audiophile
(or
both)
you
have
probably
noticed
that
much
of
the
excitement
of
a
live
performance
is
missing
in
a
recorded
or
broadcast
per-
formance.
The
primary
reason
for
this
loss
of
excitement
is
that
the
dynamic
range
of
the
recorded
or
broadcast
per-
formance
has
been
purposely
restricted
to
fit
the
dynamic
range
limitations
of
the
recording
or
broadcast
medium.
The
2BX
is
a
sophisticated
expander
that
can
restore
the
dynamic
range
and
excitement
to
a
recording
or
radio
broadcast,
adding
considerably
to
your
listening
enjoyment
By
expanding
dynamic
range,
the
2BX
lowers
the
characteristic
noise
levels
of
a
tape,
phonograph
record
or
FM
broadcast.
It
restores
the
"punch"
of
loud
passages
and
the
whisper
of
quiet
ones.
It
can
add
new
life
to
an
old
record
collection,
and
make
FM
broadcasts
worth
listening
to.
The
use
of
a
2BX
with
a
dbx
tape
noise
reduction
system
(such
as
our
120
or
150
series),
lets
you
make
tape
copies
of
records,
FM
broadcasts
or
other
tapes
that
actually
sound
better
than
the
original.
With
these
capabilities,
the
2BX
will
become
one
of
the
most
valued
components'
in
your
home
music
system.
CONNECTIONS
AC
POWER
Connect
the
2BX
to
a
117V
AC,
50
or
60Hz
power
source
only.
The
2BX
requires
20
watts
of
AC
power
(maximum).
As
a
precaution,
do
not
connect
the
AC
power
cable
until
all
signal
connections
have
been
made.
(Models
for
use
with
foreign
power
sources
are
available
Contact
the
dbx
factory
for
information.)
SIGNAL
CONNECTIONS
NOTES:
1.
If
you
do
not
have
a tape
recorder,
do
not
connect
anything
to
the
TO
TAPE
RECORDER,
or
the
FROM
TAPE
RECORDER
jacks.
2.
With
the
setup
in
Figure
2,
changes
in
preamp
volume
will
require
adjustment
of
the
2BX
transition
level.
3.
If
you
do
have
a
tape
recorder
and
wish
to
expand
before
you
record,
use
the
connections
shown
in
Figures
1
2
or
3.
*
4.
If
you
have
a
dbx
tape
noise
reduction
system
see
Page
9.
Connect
the
2BX
to
your
system
according
to
one
of
the
following
diagrams:
LOCATION
FOR
OPTIONAL
REVERB
LOCATION
FOR
-
OPTIONAL
GRAPHIC
EQ
*NOTE:
2BX will
reduce
reverb
noise,
but will
also
shorten
decay
time.
—
—
OPTIONAL
RECORDER
—
i
Fig.
1
—
How to
Connect the
2BX
to
Your
Receiver,
Preamplifier
or
Integrated
Amplifier.
This is
the
preferred
hookup
assuming
a
tape
monitor
loop
is
available.
LEFT
x
D
LT<0
RT
O
f
o
2
o
h
O
SojJ
o
o
o
o
PREAMP
dfc»
•LpH
AH
MAIN
AMP
I
I
(.LOCATION
OF
^•"^OPTIONAL
REVERB
|
OR
GRAPHIC
EQ*
I
*NOTE:
2BX will
reduce
reverb
noise,
but
will
also
shorten
decay time.
OPTIONAL
RECORDER
.
Fig.
2
-
How
to Connect
the
2BX if a
tape
monitor
loop
is
unavailable
and
you are
using
a separate
preamp
and
power
amp
(or
between
preamp
out
and
main amp
in
jacks).
Fig.
3
-
How
to
Connect
the
2BX
in
the
Tape
Monitor
Loop
of
a
Graphic
Equalizer
or
Speaker
Equalizer.
OPERATION
NOTES:
1.
For
a
description
of
control
functions,
see
the
BRIEF
OPERATING
INSTRUCTIONS
at
the
front
of
this
manual.
2.
If
you
do
not
have
a
tape
recorder
connected
as
shown
in
Figures
1
through
3,
press
IN
the
SOURCE
and
PRE
buttons.
3.
To
avoid
repetition,
we
will
use
the
word
"amplifier"
to refer
to
your
receiver,
preamplifier
or
integrated
amplifier.
EXPANSION
To
Expand
an
FM
Broadcast
or a
Conventional
Phonograph
Disc
1.
With
your
amplifier's
master
volume
control
all
the
way
down,
turn
on
the
AC
Power
for
your
entire
system.
2.
Select
the
desired
source
(FM
or
disc)
on
your
amplifier's
selector
switch.
3.
Place
2BX
in
SOURCE
and PRE
mode
(SOURCE
and PRE
buttons
IN).
4.
Set
the
EXPANSION
RATIO
and
the
TRANSITION
LEVEL
(threshold)
controls
to
approximately
mid
position.
5.
With
the
music
playing,
readjust
the
TRANSITION
LEVEL
control
until
red L.E.D.
GAIN
CHANGE
indicators
glow
on loud
passages,
and
the
yellow
L.E.D.
GAIN
CHANGE
indicators
glow
on
quiet
passages*.
*The
L.E.D.
GAIN
CHANGE
indicators
show
the
relative
amount
of
expansion
produced
by
the
2BX
in
each
of
its
two
frequency
bands.
When
one
or
more
red
L.E.D.
's
light
in
a
given
band,
the
2BX
is
raising
the
program
level
in
that
band.
When
one
or
'
more
of
the
yellow
L.E.D.
's
light,
the 2BX
is
lowering
the
program
level
in
that
band.
The
number
of
L.E.D.
's that
light
correspond
to the
relative
amount
of
expansion
up
to the
maximum
dis-
play
able
range.
More
upward
or
downward
expansion
can
be
achieved
than
is
shown
on
the
display.
6.
Slowly
bring
up
your
amplifier's
master
volume
control
to
the
desired
listening
level.
7.
Readjust
the
EXPANSION
control
for
the
desired
amount
of
expansion.
This
will
depend
on
the
program
being
expanded.
For
a
good
classical
phonograph
disc,
an
expansion
ratio
of
1:1.1
or 1:1.2
(settings
of
1.1
or
1.2)
may
be
optimum.
For
a highly
compressed
FM
broadcast,
an
expansion
ratio
of 1
:
1.4
or 1
:
1.5
(settings
of
1.4
or
1.5)
may
produce
better
results.
If
you're
not
sure
where
to
set the
EXPANSION
control,
start
at
a
low
setting,
and
move
it
higher
until
it
sounds
extreme,
then
move
the
control
back
so the
sound
is
natural
again.
The
degree
of
expansion
desired
also
depends
on
the
mood
of
the
listeners.
Generally,
you
will
desire
larger
amounts
of
expansion
when
you
are
totally
involved
with
the
music.
To
Expand
a
Tape
During
Playback
Follow
the
instructions
above
for
expanding
an
FM
broadcast
or
conventional
phonograph
disc,
except
place
the
2BX
in
TAPE
and
POST
mode
(TAPE
and
POST
buttons
IN).
It
is
not
necessary
to
expand
a
dbx-encoded
tape
after
decoding
(during
playback)
if
the
tape
has
already
been
2BX-expanded
prior
to
recording.
If
you
have
two
tape
recorders
only
one
TAPE
input,
and
you
use
one
recorder
primarily
for
playback,
plug
it
into
your
amplifier's
AUX
INPUTs;
then
follow
the
directions
for Ex-
panding
an FM
Broadcast
or
a
Conventional
Phonograph
Disc
(as
already
described).
How
to
Expand
and
Tape
Record
a
Program
NOTE:
Expanding
a
program
and
then
recording
it may
cause
the
dynamic
range
of
the
program
to
exceed
the
dynamic
range
of
your
tape
recorder.
This
could
add
distortion
and/or
excessive
tape
noise
to
the
recording.
Loading...