BGW 250 Owner's Manual
..
' .
OWNERS
MANUAL
MODEL
250
STEREO
POWER
AMPLIFIER
S
ER IAL
~JUMBER
rJ
4/1'='
BGW
SYSTEMS
P.O.
BOX
3742
BEVERLY
HILLS, CALIF.
90212
..
H1PORTArJT
--PLEASE
READ
THIS
PAGE
BEFORE
OPERATING
YOUR
BGW
POWER
AMPLIFIER
YOUR
NEW
RGW
POWER
AMPLIFIER
IS
DESIGNED
TO
PROVIDE
YEARS
OF
TROUBLE
FREE
PERFORt"1ANCE.
OnSERV I NG
THESE
Fnl
PRECAUT
IONS
WILL
INSURE
PROPER
OPERATION.
ilEVER
CONNECT
THE
OUTPUT
OF
OtlE
CHAWJEL
\'IHI
THAT
OF
M!OTHER.
l'
lEVER
CONNECT A DIRECT
SHORT
FROM
THE
OUTPUT
OF
ANY
CHANNEL
TO
GROUND.
ONLY
CONNECT
THE
POWER
COgD
I8
THf
PROPE~
MAINS
(NORMALLY
THIS
WILL
BE
lO~-12
VOkTS
AC
~O-6UHZ).
SEE
SECTI
ON
~t_
FOR
CONVERS
ION
TO
L4u
VOLT
OPERAT ION.
ONLY
MAKE
CONNECTIONS
TO
THE
POWER
AMPLIFIER
~IITH
THE
POWER
OFF.
Do
NOT
REMOVE
FACTORY
SEAL.
AMPLIFIERS
~IILL
NOT
BE
COVERED
UNDER
WARRANTY
IF
SEAL
IS
BROKEN.
THERE
ARE
.tlQ.
ADJUSTMENTS
~/ITHIN.
'. .
TABLE
OF
1.
DESCRIPTION
2.
SPECIFICATIONS
3.
WARRANTY
4.
FACTORY
SERVICE
5.
INSTALLATION
A.
UNPACKING
B.
MOUNTING
C.
OUTPUT
CONNECTIONS
D.
INPUT
CONNECTIONS
E.
nC
MAINS &CONVERSION
6.
OPERATION
7.
SCHEMATIC
DIAGRAM
8.
PARTS
LST
9.
WARRANTY
REGISTRATION
FORM
10.
SERVICE
AUTHORIZATION
FORM
..
.
CONTENTS
TO
240
VOLTS
I .
J .
" .
I-DESCRIPTION:
The
BGW
250
is
the
most
advanced
dual
solid
state
power
amplifier
available.
The
basic
design
criteria
used
are
those
which
are
applied
to
present
day
computers
and
related
equipment.
Unique
design
features
incorporated
in
the
250 make
it
virtually
"FAIL
SAFE"
and
free
from
accidental
damage
caused
by
human
error
in
audio
service.
A
fast
acting
SCR
(silicon
controlled
rectifier)
crow
bar
is
employed
as a safe
guard
for
your
speakers.
The
sophisti-
cated
sensing
circuitry
for
the
crow
bar
constantly
samples
the
individual
outputs
of
each
channel.
The
outputs
of
each
channel
are
integrated
and
passed
through
an
absolute
value
detector.
The
output
of
the
detector
is
connected
to a compar-
ator
which
is
activated
by
the
presence
of a large
DC
component.
If
such a voltage
is
present
the
comparator
in
turn
triggers
a
fast
discharge
pulse
circuit
which
fires
the
SCR
crow
bar.
The
crow
bar
is
essentially
a
direct
short
placed
across
the
two
power
supplies-
If
activated
this
causes
abnormally
high
current
to
flow
in
the
primary
circuit
and
within
a
fraction
of a second
the
ultra
fast
acting
circuit
breaker
disconnects
the
power.
The
crow
bar
circuit
quickly
discharges
all
energy
stored
in
the
power
supply
internally,
not
into
the
speaker;
thus
protecting
the
load.
The
packaging
inside
your
250
is
unlike
ordinary
power
amplifiers.
Each
channel
assembly
is
on
its
own
separate
module,
which
simply
plugs
in
or
out
for
quick
and
easy
service.
Each
of
these
units
is
constructed
on a tremendous
aluminum
extrusion.
The
total
radiating
surface
area
of
each
heat
sink
is
330
square
inches.
The
heat
sinks
have
mating
circuit
boards
which
carry
the
passive
components.
Each
unit's
wiring
is
identical
with
the
next
as
the
circuits
are
photo
etched.
The
heat
sinks
plug
in
with
an 8 pin
connector.
The
output
stage
of
your
250
uses
the
most
powerful
type
of
transistors
available.
The
large
geometry
single
diffused
devices
have
the
largest
safe
operating
area
of
any
type
of
transistor
available.
All
the
semiconductors
in
the
output
stage
are
in
intimate
contact
with
the
heat
sink.
The
dynamic
bias
circuit
is
also
mounted
on
this
isotherm
providing
rock
steady
bias
stability
with
temperature.
The
voltage
gain
circuits
are
also
mounted
on
the
same
circuit
card.
A
true
operational
amplifier
integrated
circuit,
hermetically
sealed
in a metal
can,
acts
as
the
front
end.
The op
amp
(as
they
are
called)
is
a
special
unit
featuring
high
speed
(15MHz)
and
high
slew
rate
(50
volts/microsecond)
yet
still
having
very
low
noise
due
to
its
darlington
input
stage
and
careful
design.
The op
amp
stage
is
followed
by a
discrete
complementary
pair
acting
as
an
active
current
source/sink
and
providing
additional
voltage
gain.
The
current
source
is
the
ideal
way
to
drive
the
output
stage
which
is
basically
a
voltage
follower.
This
sophisticated
circuit
design
makes
for
an
extremely
accurate
amplifier.
The
open
loop
gain
is
higher
than
found
in
the
competitors'
products.
The
accuracy
of
an
amplifier
is a function
of
the
difference
between
the
open
loop
gain
and
the
closed
loop
gain.
In
this
case
the
closed
loop
gain
is
26
db
(a
voltage
gain
of
only
20)
while
the
open
loop
gain
is
about
1,000,000.
The
accuracy
of
the
250
is
so
great
that
conventional
audio
test
equipment
is
unable
to
provide
meaningful
measurements.
Harmonic
distortion
Measurements
are
simply
the
residual
level
of
the
distortion
analyzer.
This
extremely
accurate
signal
processing
enables
the
250
to
drive
speakers
at
very
high
levels
while
adding
absolutely
no
coloration
of
its
own.
EVen
at
milliwatt
levels
the
output
waveform
exhibits
no
sign
of
crossover
distortion.
The
dynamic
range
capability
of a typical
250
is
almost
115
db.
.
..
'
f'
2-
SPECIFICATIONS
TIle
following
specifications
are
guarranteed
mInImum
perfor-
mance
levels,
not
typical
or
best
cnse
numbers
measured
under
ideal
conditions.
All
test
procedures
used
are
according
to
the
most
conservative
techniques
in
use
today.
POWEK
OUTPUT:
8S-watts
average
continuous
power
per
channel
at
8-ohms.
FRf,QIJENCY
R[SPONSE:
+0-0.25
dB
201lz
to
20KHz
+0-3
dB
211z
to
65
Kllz
HARMONIC
DISTORTION:
Less
than
0.1%
at
85
watts
per
cnannel
or
less
into
8 ohms.
1M
DISTORTION:
(00 & 7khz
4:1):
Less
than
.l~
at
85
watts
per
channel
or
less
into 8 ohms.
tfUM
&
NOISE
(20-20
kHz):
105
dB
below
HS
watts
into
8
oj~s
INPUT
SENSITIVITY:
I
volt
+2%
for
20
volts
out
(SO
watts,
8 ohms)
voltage-gain
of
26
db
(20xL
1.5
volts
required
for
full
outpuL
INPUT
H!PEDANCE:
47,000
ohms
DAMPING
FACTOR:
Greater
than
500
at
low
frequencies
(8 ohms )
OUTPUT
LOAD
H1PEDANCE:
Designed
for
any
load
impedance
greater
than
2 ohms.
Haximum
output
po'veT
occllrs
rtt
2
()l'r~.
RISE
TIMBrIO-90t):
5
micro5cconds-
inuicat.ing
a
bandwidth
of
(IS
KlIz.
POWER
BAND:
10
Hz
to
20 kHz.
POWER
REQU
I
REr-IENT
:
105-120
volts
50-60Hz
at
5 amps maximum
or
210-240
volts
at
2.5
amps maximum.
TURN
ON:
Anti
surge
turn
on,
no
switching
transients
or
thump
wil
l
appear
at
output.
OUTPUT
PROTECTION:
Each
channel
is
p~otected
against
shorts,
open
circuit
opcration,
mismatched
loads,
etc.
LOAD
PROTECTION:
Exclusive
SCR
crow
bar
protccts
speakers
against
malfunction.
OVERALL
PROTECTION:
Power
line
is
protected
with
fast
acting
computer
type
,
circuit
breaker.
No
fuses
of
any
kind
are
used.
Two
thermal
switches
(one
per
channel)
protect
against
over
temperature
operation.
Controlled
power
bandwidth
and
slew
rate
protect
tweeters
and
amplifier
against
excessive
high
frequency
operation.
Input
overload
protection
is
afforded
op amps
by
series
limiting
resistance.
POt\,ER
SUPPLY:
A
large
power
transformer
with
twin
primary
windings
is
used.
Computer
grade
electrolytic
capacitors
storing
over
22
joules
of
energy,
and
a 25
amp
bridge
rectifier
are
employed.
Two
Zener
regulated
supplies
power
each
operational
amplifier
front
end.
POWER
REQUIREHENTS:
Unit
requires
either
10S-129V
AC
or
210-240V
SO-60Hz
power.
A 5
amp
circuit
breaker
is
supplied
for
units
Hired
for
120V
operation
or a 2.5
amp
breaker
for
240V
operation.
HEAT
SINKING:
Each
channel
has
its
own
removable
heat
sink.
Each
extrusion
has
330
square
inches
of
surface
nrea.
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