CES : BGW Professional Series

BGW Power Amplifiers

...For an Imperfect World
Building an amplifier that tests beautifully is hard enough: Translating laboratory results into real world performance is something else entirely. The Model 750 was the first to show that both are possible. Today's fourth generation 750G raises the standards other professional amplifiers must meet. Ruggedness, reliability, serviceability, DC speaker protection and electrical safety receive the same meticulous design scrutiny as the factors that produce the 750's outstanding level of audio accuracy - so do input switching flexibility and informative metering.

Unmatched Thermodynamic Engineering
Reducing transistor temperature changes by 10 degrees Centigrade extends the operating life by 50% - the 750G is totally free from thermal cycling fatigue failure, the power transistors failure mode that limits long term reliability. Each of the 24 Ultracase transistors used in the Model 750G has its own solid copper header. This unique flat pack design allows for vastly improved heat transfer to the heavy aluminum heat sinks. With more than three times the active surface area of the conventional steel packaged (TO-3) transistors used by other manufacturers, BGW Ultracase transistors can handle twice the heat. Each Ultracase transistor is rated at a full 200 watts dissipation: total available dissipation is 4800 watts. Despite the very wide Safe Operating Area of BGW transistors, over 10 pounds of aluminum is used in the heat sinks to effectively absorb thermal transients and minimize fluctuations in transistor temperature.

Unlike power MOSFETs, Ultracase output devices do not require bias power. The driver stage uses the same power devices and runs in class AB operation. In the 750, power MOSFETs would have to dissipate an additional 150 watts of power - with no input signal. 750s have always enjoyed a reputation for running cool: That ability is the foundation for their outstanding reliability.

Along with the design of the transistors and heat sinks, the third reason for the 750's remarkable thermal stability is the simple, effective, often-imitated BGW cooling system. A heavy duty two speed industrial fan on the rear apron draws as much as 70 cubic feet of air through the amplifier each minute, cooling the heat sink modules with fresh air drawn in through the side vents. Hot air is exhausted through the back of the amplifier.

To keep the output transistors inside their Safe Operating Area, thermostats mounted on each channels heat sink module automatically switch the fan to high speed as soon as the heat sink temperature reaches 55 degrees Centigrade. When the Fan Defeat switch is engaged, as in studio control room applications, the thermostats will automatically start the fan in high speed, if the heat sink temperature exceeds these conservative operating limits.

DC Speaker Protection
And Turn-on Delay Without Relays

Electro-mechanical relays used to be a weak point in the reliability of professional power amplifiers. Some manufacturers have used that fact as an excuse for eliminating the speaker protection function provided by those relays: BGW engineers have replaced them with innovative solid state protection devices.

Primary mains protection has been combined with the on/off switch in a rocker-actuated magnetic circuit breaker which is mounted on the front panel. Along with superior convenience, the magnetic circuit breaker allows more predictable operation because it is independant of operating temperature.

Turn-on transients are annoying at best, damaging to expensive drivers at worst. The 750's electronic turn-on delay prevents signals from reaching the outputs for three to five seconds after power is turned on. This delay gives the entire signal chain time to stabilize.

The 750's sophisticated short circuit protection allows it to drive 2 ohm loads without false triggering. The amplifier protects itself automatically if speaker leads do become shorted, and the front panel true clip indicator flashes to warn the operator of the problem.

Finally, a thyristor crowbar circuit built into each heat sink module prevents DC from burning up your speakers in the case of catastrophic amplifier failure. Most other amplifiers simply ignore this crucial form of speaker protection.

Thermal protection is just as extensive: Thermostatic switches monitor the heat sinks, shuting down the amplifier if their temperature exceeds 90 deg. C (operation will resume as soon as the fan has had a chance to cool the amplifier). The transformer is also protected by its own built-in thermal circuit breaker, which triggers at 110 deg. C and automatically resets itself once a safe temperature is reached.

Ultra-Rugged Chassis and Wiring
Over two decades of professional use, the 750 has endured every form of punishment the road has to offer. The welded steel 750 chassis is the result of that experience - it's the only material tough enough to withstand all the abuse encountered by touring sound systems. In our tests, 750s have been dropped on a concrete floor from three feet and have sustained impact forces of hundreds of Gs with minimal damage.

A tough outer casing is useless unless the components inside are equally shock resistant. BGW tests all available interconnects and uses only the strongest types available (not the modular telephone jacks used by some of our competitors). The labor intensive wiring harness is designed to handle severe shocks and intense vibration.

Flexible Configurations and Controls
Since BGW 750s are used for nearly every professional audio application, the Model 750G has newly designed inputs and other operational features that enhance their versatility. The standard high performance active balanced input module includes both male and female XLR connectors as well as 1/4" phone jacks, an arrangement that facilitates "daisy-chaining" a rack of amplifiers. In addition, a switched 1/4" input jack allows direct connection to the power amplifier's single ended input, thus bypassing the active balanced inputs. For bi-amplified operation without external crossovers, the new 750s accept BGW's internal crossover cards.

Rear panel switches engage the subsonic filter and allow the amplifier to operate in dual mono mode. Ground Lift and Fan Defeat switches enable quiet operation on hum-prone power lines or in quiet control room environments.

To allow system levels to be adjusted simply and repeatably, we use precision stepped attenuators as the front panel gain controls. Each step is calibrated in decibels and clearly marked on the front panel.

Informative Metering and Displays
The front panel of the 750G is designed to communicate all necessary information quickly and clearly to the operator. It provides Modulation and True Clip indicators that provide the immediate indication of operating conditions required in many applications. The Model 750G goes beyond those essentials with a wide dynamic range LED VU meter which uses 20 rectangular green, yellow and red lamps on each channel. This meter display can be read easily, even from across a stage.

The seperate True Clip indicator is twice the width of the last red LED. The dedicated circuits which drive this lamp detect the loss of feedback should the amp be driven into clipping or the speaker leads become shorted. The circuitry tracks load impedance and power line voltage changes, and is activated whenever the amplifier exceeds its linear operating range. This display can be very useful in setting and maintaining system levels, in monitoring compression and dynamic range, and in keeping track of each amplifier in large systems.

Other 750G status indicators include a pair of DC offset lights, a seperate overtemperature light which indicates transformer temperatures above 110 deg. C, and a Power Supply failure warning light.

Outstanding Performance in Demanding Applications

Fixed Installations
Whenever superior audio performance and low maintenance are important criteria, BGW 750s are the inevitable choice. From clubs to churches, airports to auditoriums, 750s have been serving the needs of exacting sound contractors for over two decades. The Model 750G is equipped with advanced features designed to simplify installation design while providing sound of the highest quality.

Touring Systems
Simply put, no one in the world builds amplifiers the way BGW does. Model 750s are especially suitable for portable applications where natural, lifelike reproduction at high volume levels is an important consideration. Their ultra-rugged construction and long list of professional features reflect years of touring experience.

Film Production and Projection
The original BGW 750 was designed to "make the earth move" in the motion picture Earthquake's Sensurround system. Since that time, a number of leading film studios, production houses and theater chains have come to rely on BGW 750s for every kind of film-related application - dubbing stages, soundtrack monitoring, all the way to projection. BGW amplifiers are THX approved, and in use at such prestigious theaters as the Academy of Motion Picture Arts and Sciences, the Directors' Guild, the Cinerama Dome, and I-Max and Omni-Max theaters.

Recording and Audio Production
Driving massive studio monitors to ear-splitting levels while maintaining the clarity of every detail is no easy task for an amplifier. Add in the continuous operating conditions of a successful studio's control room, and you have perhaps the ultimate "real world" test of a professional power amplifier. BGW 750s have been passing that test with flying colors for well over a decade. The newest Model 750G, with ultra-high speed output transistors and active balanced inputs, are better equipped than ever to provide the uncompromising accuracy needed for digital recording and mixing.



Thanks to BGW
We would like to thank BGW for allowing us to place this information on our website. Any reproduction of information from this page must go through BGW for permission.