Micro-Tech 2400 Amplifier Service Manual

Theory

 

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.

 

As the input drive voltage becomes more positive, the

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

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

 

the positive half, and about .5V across the bias resistor

The output of the +LVA drives the base of predriver

in the negative half. Q18 conduction (and thus bias) is

device. Together, the predriver and driver form the

adjustable.

first two parts of the three-deep Darlington and are

 

biased class AB. They provide output drive through

A diode string prevents excessive charge build up

the bias resistor, bypassing the output devices, at

within the high conduction output devices when off.

levels below about 100mW. An RLC network between

Flyback diodes shunt back-EMF pulses from reactive

the predriver and driver provide phase shift compen-

loads to the power supply to protect output devices

sation and limit driver base current to safe levels.

from dangerous reverse voltage levels. An output

Output devices are biased class B, just below cutoff.

terminating circuit blocks RF on output lines from

At about 100mW output they switch on to conduct high

entering the amplifier through its output connectors.

current to the load. Together with predriver and driver,

 

the output device provide an overall class AB+B

Low Side (LS)

output.

The Low Side (LS) operates quite differently. The

 

power supply bridge rectifier is not ground refer-

The negative half of the HS is almost identical to the

enced, nor is the secondary of the main transformer.

positive half, except that the devices are PNP. One

In other words, the high voltage power supply floats

difference is that the PNP bias resistor is slightly

with respect to ground, but ±Vcc remain constant with

greater in value so that PNP output devices run closer

 

+

 

+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 2400 service manual High Side HS, Low Side LS
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2400 specifications

Crown Audio is a well-respected name in the audio industry, known for its powerful and reliable amplifiers. Among its notable products is the Crown Audio 2400, a high-performance amplifier that has garnered attention for its impressive range of features and technologies.

The Crown 2400 is part of the XTi series, which is renowned for delivering exceptional sound quality and performance. A key feature of the 2400 is its innovative Class-I technology. This design allows the amplifier to remain highly efficient while producing substantial power output, making it suitable for a variety of applications, from live sound to installation settings. With a power rating of 2400 watts per channel at 4 ohms, the XTi 2400 provides ample power for driving multiple speakers, ensuring that audio can fill even the largest spaces.

Another standout characteristic of the Crown 2400 is its built-in DSP capabilities. This onboard digital signal processing allows users to tailor the audio output to their specific needs. The DSP features include adjustable crossover settings, EQ adjustments, delay settings, and limiting functions, all accessible through an intuitive LCD interface. This user-friendly design enables quick adjustments in real-time, which is critical in dynamic live performance environments.

The amplifier also boasts advanced connectivity options, including both XLR and 1/4-inch input connectors, allowing for versatile integration with various audio sources. Additionally, the inclusion of Speakon outputs provides secure and reliable connections to speakers, minimizing the risk of accidental disconnects during performance.

Thermal management is another area where the Crown 2400 excels. The amplifier is equipped with a comprehensive cooling system, which includes a variable-speed fan and extensive heat sinking. This design ensures that the amplifier operates efficiently even under heavy load, prolonging its lifespan and maintaining optimal performance.

Finally, the Crown Audio 2400 is designed with durability in mind. Its rugged construction makes it suitable for the rigors of touring and demanding live environments, reinforcing Crown's commitment to quality and reliability.

In conclusion, the Crown Audio 2400 stands out as a powerful and versatile amplifier, offering Class-I technology, robust onboard DSP, excellent connectivity options, advanced thermal management, and durable construction. These features make it an ideal choice for audio professionals seeking reliability and high performance in their sound systems.
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