Power Base-2 & 800CSL Amplifier Service Manual

Theory

allows the NFb loop to control Error Amp gain by

 

The output of the +LVA drives the base of predriver

feeding back to its non-inverting input (with its polarity

 

device. Together, the predriver and driver form the

opposite to the output of the VGS). With the added

 

first two parts of the three-deep Darlington and are

voltage swing provided by the LVAs, the signal then

 

biased class AB. They provide output drive through

gains current amplification through the Darlington

 

the bias resistor, bypassing the output devices, at

emitter-follower output stage.

 

levels below about 100mW. An RLC network between

GROUNDED BRIDGE TOPOLOGY

 

the predriver and driver provide phase shift compen-

 

sation and limit driver base current to safe levels.

Figure 2 is a simplified example of the grounded

 

Output devices are biased class B, just below cutoff.

bridge output topology. It consists of four quadrants

 

At about 100mW output they switch on to conduct high

of three deep Darlington (composite) emitter-follower

 

current to the load. Together with predriver and driver,

stages per channel: one NPN and one PNP on the

 

the output device provide an overall class AB+B

High Side of the bridge (driving the load), and one

 

output.

NPN and one PNP on the Low Side of the bridge

 

The negative half of the HS is almost identical to the

(controlling the ground reference for the rails). The

 

output stages are biased to operate class AB+B for

 

positive half, except that the devices are PNP. One

ultra low distortion in the signal zero-crossing region

 

difference is that the PNP bias resistor is slighter

and high efficiency.

 

greater in value so that PNP output devices run closer

 

 

to the cutoff level under static (no signal) conditions.

High Side (HS)

 

This is because PNP devices require greater drive

The High Side (HS) of the bridge operates much like

 

current.

a conventional bipolar push-pull output configuration.

 

HS bias is regulated by Q18, the Bias Servo. Q18 is a

As the input drive voltage becomes more positive, the

 

HS NPN conducts and delivers positive voltage to the

 

Vbe multiplier which maintains approximately 3.3V

load. Eventually the NPN devices reach full conduc-

 

Vce under static conditions. The positive and negative

tion and +Vcc is across the load. At this time the HS

 

halves of the HS output are in parallel with this 3.3V.

PNP is biased off. When the drive signal is negative

 

With a full base-emitter on voltage drop across

going, the HS PNP conducts to deliver -Vcc to the load

 

predrivers and drivers, the balance of voltage results

and the HS NPN stage is off.

 

in approximately .35V drop across the bias resistors in

 

+

 

+Vcc (Positive Rail)

 

Input

 

 

signal

Load

 

 

 

 

(speaker)

 

 

Inverting Op-amp

 

HIGH SIDE

-Vcc (Negative Rail)

LOW SIDE

-

Figure 2. Crown Patented Grounded Bridge Topology

10

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Crown Audio 800CSL service manual Grounded Bridge Topology, High Side HS
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800CSL specifications

Crown Audio has long been a respected name in professional audio equipment, and the 800CSL amplifiers are a testament to their unwavering commitment to quality and performance. Designed for professional sound reinforcement applications, the Crown 800CSL offers an impressive blend of power, reliability, and versatility, making it a popular choice among audio engineers and event coordinators.

At the heart of the Crown 800CSL is its robust power output. This amplifier delivers an impressive 800 watts per channel at 4 ohms, ensuring that it can drive even the most demanding speakers with ease. It features a Class D design, which not only maximizes efficiency, allowing for more power with less heat generation, but also contributes to a lightweight chassis that is easy to transport and install. This makes the 800CSL a versatile option for both permanent installations and mobile events.

One of the key technologies employed in the Crown 800CSL is its comprehensive built-in protection circuitry. This includes advanced short circuit protection, over-temperature protection, and current limiting. Such features ensure that the amplifier operates reliably in challenging conditions, reducing the risk of damage to both the amplifier and the connected speakers. The inclusion of a low-frequency filter further enhances performance, providing clean, powerful bass without distortion.

The Crown 800CSL also offers a range of connectivity options, including XLR and ΒΌ-inch inputs, making it compatible with a wide variety of audio sources. This flexibility, combined with user-friendly front panel controls, allows audio professionals to set up and adjust the system quickly and efficiently.

Additionally, the amplifier features a robust and compact design with a lightweight aluminum chassis. This not only contributes to its portability but also aids in heat dissipation, further enhancing performance during prolonged use. The included handles on the chassis make it easy to transport the unit between gigs, while its durable components ensure longevity.

In summary, the Crown Audio 800CSL stands out for its power, efficiency, and reliability. From its Class D amplification technology to its comprehensive protection features, this amplifier is designed to meet the needs of professionals in the audio industry. Whether for concerts, events, or installations, the 800CSL is poised to deliver exceptional sound quality and performance, making it a valuable addition to any audio toolkit.
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