BGW 150 User manual

12300-1
!1
SYSTEMS
13130 SOUTH YUKON AVe:NUe:
HAWTHO~Ne:. CAl..lFORNIA 9C250
PHONe: ~ 973-8090
Tc!l..EX NO. 66_4494
(310)
OWNER'S MANUAL
MODEL 150
PROFESSIONAL POWER AMPLIFIER
TABLE OF CONTENTS
.FORM NU~AP,ER
DESCRIPTION
Important ................................ . ......... .. ........ .. . 1)0601
DescriDtion
01530
Specifica tions
02150
Unp acking and Set-Up
02500
Rack Mounting Hints ............................................. 02650
Stereo Input Connections ......................................... 03002
Bridging Balanced Line Inputs ..................................... 03011
Bridging Unbalanced Line Inputs ......................... . ......... 03021
Balanced Line Input ......... ...... . ..... . ...................... . . 03031
U
nbalanced Line Input
03041
Terminating Resistance Chart
03051
Stereo Output Connections ....................................... 0350 l
Damping Factor Nomagraph ...................................... 03510
Speaker Fuse'iomagraph
03530
.'vlono
Opera tion
03650
Power \ Iains Connection
ouOOO
Opera tion
052 00
Circuit Desc;-iption .......................... . ................... 123li)
Schematic Qiagram~ , -\mplifier f-leatsink ... ... ......... ... ... . .... ' . 12 380
Sch
ematic Qiag!"am, Chassis ............ , ... .. .. . . .. , . ..... , . .. , .. [2371)

12300-2
Schematic Diagram, AC wiring .................................... 12360
Block
Diagram, Power Amplifier ................................... 12350
Parts List. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 12390

00601
-IMPORTANT-
PLEASE READ THIS PAGE BEFORE OPERATING
YOUR
BGW POWER AMPLIFtER
Your new BGW amplifier is designed to provide years of trouble free performance.
Observing these few precautions will insure proper operation.
All connections should be made to the power amplifier with the power OFF.
Speaker fuses should be used to afford maximum speaker protection.
Never connect the output of one channel to that of another.
Connect the power cord to the proper voltage mains as indicated on the rear of
the amplifier. ConverSion to another voltage requires internal rewiring.
Do not remove the amplifier's cover. Amplifiers may not be covered under
warranty if they are tampered with. There are NO adjustments within.
Potentially lethal voltages exist within the amplifier. Refer all service work to
an authorized BGW service station.

01530-1
DESCRIPTION
The BGW Model 150 is one of the most advanced solid state, fully complementary,
bridgeable, stereo power amplifiers available.
Features of the Model 150 include precision step attenuator leve1 controls, LED
metering, separate circuit and chassis grounds, XLR and Y4" input connectors with
transformer sockets, and small size.
The front panel includes two vertical rows of four red LED's, one row for each
channel. The lower LED in each row is the IDLE indicator or pilot lamp. They will
be
lit whenever the amplifier is turned on.
The
top LED in each row is a clipping indicator and utilizes an exdusive BGW
circuit. Whenever either channel of the 150 is driven into clipping, a corresponding
indicator lights and remains lit for 0.20 seconds. These indicators, which actually
indicate loss of feedback, tell the operator that the amplifier is being overdriven
and can be invaluable to the engineer who must be sure that every component in his
system is producing a clean, distortion-free signal. An inadvertant short-circuited
output (with signal) will cause the LED to remain on until the short is removed.
The midd1e LED's are connected to a circuit employing integrated circuit to
provide an audio level indication of 0.5% and 50% of maximum power output. They
provide a
valuable tool for total system evaluation in multiple amplifier
installa tions.
Both the circuit and chassis grounds are connected to separate barrier strip
term inals on the rear of the amplifier. They are connected together by a
removeable link. By removing the link, the circuit grounds of all active units
(amplifiers, preamplifiers, mixers, etc.) can be tied to earth ground at a common
point. This aids in eliminating ground 1 00ps.
Ei ther XLR-type of V4 inch phone plugs may be used for input connections. If plug-
in transformers are used, the XLR-type connectors are connected. If not, jumpers
must be employed in the transformer sockets. See sections 03011, 03021, 03031,
and 03041
for details.
The size of the \t\odei 150 is convenient for a wide variety of applications.
However, please note the following precaution:
1) Do not use the front panel as the sole support for the am plifier.
Side rails or rack sheives should be employed (See section
02650).
The
output stages of your amplifier use the most advanced type of transistors
available. These large geometric, complementary, power devices have large safe
operating areas and extended power bandwidth. Electrostatic and other highly
reacti ve speaker systems present no difficulties for the .\"odel 150. The aluminum
heat sinks are located so the 150 power amplifiers can be stacked on top of each
other and air can be forced through both sides to cool the products.

01530-2
AU of the semiconductors in the output area are in intimate contact with the heat
sink. The bias circuit is also mounted on this isotherm to provide rock steady bias
stability with temperature.
The voltage gain circuits are also mounted on the same circuit board. A true
operational amplifier integrated circuit acts as the front end.
The op-amp is a special unit featuring very low noise, high speed (lOMHz). The op-
amp stage is followed by a discrete complementary pair acting as an active current
source/sink and providing voltage gain. The current source is the ideal way to
drive the output stage, which is basically a triple Darlington voltage follower.
This sophisticated circuit design makes for an extremely accurate amplifier. The
accuracy of an amplifier is a function of the ratio of the open loop gain to the
closed loop gain. In this case, the open loop gain is about 1,000,000. This
extremely accurate signal processing enables the amplifier 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.

02150-1
THE BGW 150
PROFESSIONAL POWER AMPLIFIER
Exacting design standards and unique features establish the BG W ampJifier as the
industry leader in power amplifier technology. Features such as all steel chassis
and covers, metal-case output uansistors and totally modular construction, have
set the industry standard in audio power amplifiers.
Delivering a full 50 watts per channel into 8 ohm loads and using the latest in full
complementary circuitry techniques, the Model 150 offers reliability and
performance unparalleled in the industry.
SPECIFICA TIONS: BG W MODEL 150
OUTPUT POWER
50 watts minimum sine wave continuous average power output per channel with
both
channels driving 8 ohm loads over a power band from 20Hz to 20kHz. The
maximum Total Harmonic Distortion at any power level from 250-milliwatts to 50
watts shall be no more than .05%.
75 watts minimum sine wave continuous average power output per channel with
both channels driving 4 ohm loads over a power band from 20Hz to 20kHz. The
maximum Total Harmonic Distortion at any level from 250-milliwatts to 75 watts
shall be no more than .08%.
150
watts minimum sine wave continuous average power output monaural driving
an 8 ohm load over a power band from 20Hz to 20kHz. The maximum Tota l
Harmonic Distortion at any power level from 250 milliwatts to 150 watts shall be
no more than .08%.
*All specifications and features are subject to change without notice.

Intermodulation Distortion:
Small Signal Frequency
Response:
Hum and Noise Level:
Input Sensitivity:
Input Impedance:
Damping Factor:
Output Impedance:
Power Requirements:
Semiconductor Complement:
Dimensions:
Weight:
02150-2
SPECIFICATIONS
Less
than 0.0296 from 250 milliwatts to
rated power.
+0, 3dB, 1Hz to 100kHz,
+0, 0.25dB, 20Hz, to 20kHz.
Better than 102dB below 50 watts
(unweighted, 20Hz to 20kHz).
1.0
volts for maximum power output.
Voltage gain 26dB (20 times).
15K ohms.
Greater than 400 to 1. Referenced at 8
ohms at 1kHz.
Designed for any load impedance equal
to or greater than 4 ohms.
100, 120, 200, 220 or 240 volts 50-60Hz
350 watts.
2 Ultra-low noise Op Amp IC's, 2 level
detector Ie's, 2 delay timer IC's, 26
transistors, 4 zener diodes, 12 diodes, 8
LED's.
1
3/4" by 19" standard rack front panel.
Depth behind front panel 11Y2". (4.45cm
X 48.26cm X
29.21cm).
14 lbs. (6.37 kg) net, l8 Ibs (8.18 kg)
shipping.

02500
UNPACKING A.t\fD SET-UP
Your 8GW Power Amplifier is shipped in an advanced packing
container.
SAVE THE CONTAINER
AND ALL PACKING MATERIAL!
The container should be saved in the event the unit is moved
or shipped at some future date. Replacement containers are
available from BGW Systems for $14.00, freight included.
Inspect the unit for damage in transit immediately upon re-
ceipt. If damage is found, notify the transportation company
immediately. Only the consignee may institute a claim with
the carrier for shipping damage. 8GW will cooperate fully ~n
such event. Be sure to save the container as evidence of
damage for the shipper to inspect.
The amplifier's mounting position must be chosen carefully so
that the air flow to the sides of the unit is not restricted.
Inadequate ventilation may cause the prot"'ecti',e heat sensors
to shut the ~nit off. For rack mounting, the four rubber
feet on the bottom of the unit may be removed and no hardware
will be loosened inside the unit.
DO NOT PLUG THE AMPLIFIZR IN YET!
All connections should be made before power is applied.

02650
RACK MOUNTING HINTS
KEEPING IT
COOL
A power amplifier draws energy from a primary electrical service, usually a 120
VAC outlet, to drive loudspeaker systems with an audio signal. Typically, only half
of the energy can be delivered to the loudspeakers; remaining energy is converted
into heat, and must be dissipated (ventilated) into the air.
Air circulating past heat-producing components, absorbs the heat and carries it
away. To accomplish this, low and medium power amplifiers rely on natural
convection currents, while most high power amplifiers use fans. If the air flow is
impeded, the resulting rise in heat may cause an amplifier to stop working or fail.
Circulating air currents must not be cut off when installing power amplifiers in
racks. Power amplifiers using convection cooling require spacing between
amplifiers to permit air flow between them. Power amplifiers using forced-air
cooling, on the other hand, can usually be stacked closer to each other and may not
need any blank panel spacing between amplifiers.
To improve natural convection currents within a rack, a chimney can be created by
closing the back of the rack and venting the rack at the bottom to let in fresh air,
and at the top to exhaust hot air. Vents should be large rectangular slots
approximately 19" wide by 4." high.
The
rack cabinet will require some type of blower if a large air-flow is required. It
is best to exhaust air from the top of the rack rather than to blow it in from the
bottom. There will be less dust and dirt in the rack this way, if the bottom vent is
sufficiently large.
INSTALLING THE UNITS
Use care when mounting equipment in a rack. Place the heaviest units near the
bottom of the rack and fill in all unused rack spaces with blank panels. Equipment
cannot always be supported by front panels alone. This is especially true of
amplifiers whose depth is more than twice their height. Uniform support can be
insured by instaUing bottom or side rails.
When racks are to be transported or used in a mobile installation, some means of
securing the rear of the equipment are required. Angle brackets either attached to
the bottom, side rails or rear panel are practical approaches.

03002-1
STEREO INPUT CONNECTIONS
Three-pin XLR and }1. in. phone jacks are provided on the rear of the amplifier for
inpult
connections. Balanced or unbalanced lines may be used; however if input
cables are longer than 8 feet, balanced lines may be necessary to maintain the
signal-to-noise ratio and high frequency response.
1/4- INCH PHONE JACKS
The 114" phone jacks are for unba l anced lines only (single conductor, shielded) and
may be used
directly. Simply connect the shield to the outer sleeve of the plug and
the inner conductor to the tip, or buy ready-made cables. See diagram below.
CONNECT SHIELD HER~'-
JJ -r ~ t 10
CONNECT INNE! CONDUCTOR HERE SLEEVE TIP
"
3-PIN XLR CONNECTORS
The 3-pin XLR connectors may be used with balanced (2-conductor, shielded) or
unbalanced lines. They are connected to the amplifier's inputs by using the 8-pin
transformer socket; they cannot be used directly.
Unbalanced Lines
To use
the 3-pin XLR connectors with unbalanced lines, a jumper plug (BGW PiN
1350-0108) must be inserted into each transformer socket. The jumper plug
connects pin III to pin 117, and pin 116 to pin 118 as shown.
With the jumper plug
in
place, the 3-pin
XLR
connector has pin
JUMPER PLUG #2
connected "to
MUST BE USED
ground, and pin 113 to
WITH
the input of the
UNBALANCED
amplifier. Note: Rear
LINES of plug shown.
When using single
conductor shielded cable for unbalanced lines, connect the inner
conductor to pin 1/3 and the shield to pins 111& 112.
J--~
When using 2-conductor shielded cable for unbalanced lines, connect the high level
signal wire to pin 113, the low level signal wire to pin 112, and the shield to pin Ill.
Note: Shield not
connected to anything
at signal source.

03002-2
To achieve a true balanced input, it is necessary to use one transformer for each
input. These should be plugged into the octal sockets provided. Depending on the
specific application, one of several different transformers may be selected.
Forms are included in this manual to help guide you in your use and selection of
transformers. Use the index below to find the appropriate form to match your
needs.
CONNECTING ON SOURCE TO ONE AMPLIFIER
Using
Balanced Lines: Refer to form 1103031
Using Unbalanced Lines: Refer to form 110304-1
CONNECTING ONE SOURCE TO TWO OR MORE AMPLIFIERS OR DEVICES
Using
Balanced Lines: Refer to form 1103011
Using Unbalanced Lines: Refer to form 1103021
NOTE: Each amplifier input will be referred to as the "Load" in the above
mentioned forms. Only one channel will be shown.
Two
conductor shielded cable should be used in a balanced line system. Connect
input cables as shown below.
Pin If1 Shield (Ground)
Pin
{"2 Signal (Minus)
Pin
113 Signal (Plus)
-"~
}I-L.,.=::::::!-~- 3
FOR MONO (BRIDGED) OPERATION
To
operate the unit as a mono amplifier, use the left channel input only. DO NOT
use
the right channel input. Remember to place the stereo/mono switch in the
mono position.

I
r(
load
112
03011
BRIDGING BALANCED LINE INPUTS
Used only when
two or more devices are driven from the same input line.
r-,
3
I
600 ohm 2 W 1 I
SOURCE 1
r---!
r<
D
~
I--
)
~
1000-
load I load
III liN
MAXIMUM NUMBER OF AMPLIFIER 25ea
Input transformers for above
A. Use 1: 1 transformer 600 ohms to 600 ohms
B. Nth load must have a terminating resistor added to the secondary
of the Input transformer.
r
One alternative configuration is
.
C. l: 1 transformer 15K ohms to 15K ohms
D. Nth load must have a terminating resistor added to the primary
of the input transformer.
To find this resistance value see sheet TERMINATING RESISTANCE CHART,
MFRM 03051.
NOTE:
Terminating resistance is required when source is a transformer. Sources
other than a transformer may not need a termination.

03021
BRIDGING UNBALANCED LINE INPUTS
Used only when two
or more devices are driven from the same Input line.
600 ohm HI . ~~------~------------~--------~
SOURCE LO
load
111
load
112
load
liN
The Nth load should have a
terminating resistor added to its octal plug between
pin 1 and pin 6.
To find this
resistor value see sheet "TERMINATING RESISTANCE CHART",
MFRM 03051.
NOTE: Terminating resistance is required when source is a transformer. Sources
other than a transformer may not need a termination.

03031
BALANCED LINE INPUT:
Used only when one
amp~ifler is driven from one source.
600 ohm / _'
-,
.....-....
\ } ( ) LOAD
Source -I
Input transformer for above
A. Use 1:5 transformer 600 ohms to 15K ohms
NOTE: No 600 ohm TERMINA nON IS REQUIRED
B. Alternate transformer
Use 1:! transformer 600 ohms to 600 ohms
NOTE:
600 ohms termination is required on the secondary of the transformer
NOTE: Terminating resistance is required when source is a transformer: sources
other than a transformer may not need a termination.
600 ohm termination, when required, can be accomplished by soldering the resistor
across pins 1 and 6 of the transformer as shown below
600 6HMS
or by installing the resistor in a 1/4" phone plug and inserting it into the unused
unbalanced input jack.

03041
UNBALANCED LINE
INPUT
Used only when one amplifier is driven from one source
600 ohm 1
..... \ ,
....... \
LOAD
\ I
\ -'
-.
Source
A 600 ohm terminating resistor-- must" be added to its octa! plug.
Between pin 1 and pin 6
NOTE: Terminating
resistance is required when source is a transformer. Sources
other than a transformer may not need a termination.
600 ohms

03051 ·
TERMINATING RESISTANCE CHART
How to find terminating resistance for balanced or unbalanced
600 ohm lines, driving more than one amplifier.
STEP
A *Input Impedance of Amplifiers
= Total Load Impedance
Number of Amplifiers of Amplifiers
STEP B
Total Impedance of Amplifiers -600 K (Impedance
=
Factor)
600
STEP
C (
t+~ x 600 ohms = Load Resistor Required
EXAMPLE:
Input Impedance of Amplifiers = 15,000 ohms
Number
of Amplifiers = 4
A
1~,000 = 3750 ohms
B
3750-600
600 = 5.25
1
C
5.25 +1 x 600 = 1.19 x 600 = 714.29 ohms
Closest value is 715 ohms 1% metal film resistor.
* Note all amplifiers must have the same input impedance. If
not, use formula below:
i =
Total Load Impedance
EXAMPLE:
Four (4) Amplifiers with input impedance of 15k,
30k, 30k and 7.5k
1..
= 3750 ohms
I
\ \ '-t
IS'(. + 30~ + 30K
-7.SK.

03'01-1
STEREO 0UTPUT CONNECTIONS
Two sets of five-way binding posts, on the rear' pane!, serve as output connectors,
with one black and one red binding post fOl" eadl channel. Left channel leads go to
the blnding posts marked LEFT; right channel, to those marked RIGHT.
Output leads are best connected, to the amplifier, with standard banana plugs;
however,
the five-way action of the binding posts permits the use of tinned wires
or
spade lugs.
Make
certain that the speakers are properly phased. Connect the black or minus (-)
terminal on the speaker cabinet to the appropriate black binding post on the
amplifier. Connect the red or plus (+) terminal to the red binding post. Check to
see that the stereQ-mono switch on the rear of the amplifier is in the stereo
position.
SPEAKER PROTECTION
All speakers can be damaged by having too much power applied to them. Fuse
protection is an effective - and inexpensive way of preventing this from occurring.
Ii your speaker system-does not contain a fuse or a circuit breaker, a fuse should be
placed in series with each speaker and the wire going -~o the red terminal on the
rear of - the amplifier'•.--
Maximum
protection can be obtained with fast-acting fuses. -Use the value
recommended by the manufacturer. Ii no value is specified, use the chart provided
to
select the correct value (MFRM-03530).
To use the chart, take a straightedge, such as a ruler, and line up the speaker's
impedance with its peak music power rating. The proper fuse value can then be
read from the center column. Choose a fuse that is closest to, and below,. the
value indicated. .
WIRE SIZE AND DAMPING FACTOR
The high damping
factor ot BG W ampiiiiers results in a very dean bass response.
Excessively long, and small diameter speaker wires can lower the damping factor
and distort the lower frequencies. A damping factor of at least 50 should be
maintained to insure good audio quail ty .
The relationship
between wire length and diameter, and damping factor can be
calculated using the chart (MFRM-03510) on the following page. Proceed as
follows:
1. Using a straight-edge, line up the gauge of the speaker wire with its length.
Mark o:fi the resulting source resistance where this line crosses the center
column.
2. Line up the source resistance, determined
in
step III , with the
manuiacturer's impedance* ot the speaker system.
The damping factor can
now be read.

03501-2
+The impe-:1ance
of a speaker sys-rem can be approximated by measuring the resistance
across the speaker terminals, wit.'1 the amplifier disconnected. Multiplying this
result by 1..33, gives you the approximate impedance.
Note: This method cannot be used with electrostatic speaken.

••
-l
Is
AHNIAUD
LOAO
SOUacl COltPO
lI51STAHCI
I.SISlANeI WI ••
t._1 t_eI
taneeeft.l
tAwet
.-
1\
-
IS
OAMfltNG
lO
'ACTOil
ISO
.2 1_
JOO
2-<.,....
CAaU
SO
IS
20
SOURCE RESISTA.1\lCE AND DAMPING FACTOR VS. LENGTH AND SIZE OF OUTPUT LEADS
MFRM - 03510
-.28
20

1
5
•
..
12
1.
.l
16 A
~
20
.2
25
J5
30
.00
300
200
150
lao
ao.
60
.0
30
1
20
15
PEAK
I
10
• MUSIC
POWER
(watts.
6
4
3
2
1..5
SPEAKER l
FUSE
SPEAKER
( ....... ) (
..... '
EXAMPLE : ~:z 8n, PEAl( POWER = 15 OW. Al~SWER: FUSE = 2 NIPS
FUSE SELECTOR NOHOGRAPH FOR LOUDSPEAKER PROTECTION
MFRM -03530