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Macro-Tech 3600VZ Power Amplifier

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5 Technical Information

5.1 Overview

Your

Macro-Tech VZ

amplifier incorporates several new

technological advancements including low-stress out-

put stages, real-time computer simulation of output

transistor conditions, advanced thermal management,

a modular system for signal input and processing, and

the articulated

power supplies.

Custom protection circuitry limits temperature and cur-

rent to safe levels while making the amplifier highly re-

liable and tolerant of faults. Unlike many lesser

amplifiers, it can operate at its voltage and current lim-

its without self-destructing.

Real-time computer simulation is used to create an

analogue of the junction temperature of the output tran-

sistors (hereafter referred to as the “output devices”).

Current is limited only when the device temperature

becomes excessive—and just by the minimum amount

necessary. This patented approach is called

ODEP

Output Device Emulation Protection. It maximizes the

available output power and eliminates overheating, the

major cause of output device failure.

The amplifier is protected from all common hazards

that plague high-power amplifiers including shorted,

open or mismatched loads; overloaded power sup-

plies, excessive temperature, chain-destruction phe-

nomena, input

overload damage and high frequency

blowups. The unit protects loudspeakers from DC in

the input signal, DC in the output, turn-on and turn-off

transients, and it detects and prevents unwanted DC

in the output. The amplifier is also protected from inter-

nal faults.

The patented four-quadrant topology used in the

grounded output stages is called the

grounded bridge

The

grounded bridge

topology takes full advantage of

the power supplies delivering peak-to-peak voltages

to the load that are twice the voltage seen by the out-

put devices and twice the voltage generated by the

power supplies.

The

grounded bridge

topology is ground-referenced.

Because the required current exceeds the limits of

presently available components, composite output

devices are constructed to function as gigantic NPN

and PNP devices. Each output stage has two compos-

ite NPN and two composite PNP devices.

The devices connected to the load are referred to as

“high-side NPN and PNP” and the devices connected

to ground are referred to as “low-side NPN and PNP.”

Positive current is delivered to the load by increasing

conductance simultaneously in the high-side NPN and

low-side PNP stage, while decreasing conductance of

the high-side PNP and low-side NPN in synchrony.

The two channels may be used together to double the

voltage (Bridge-Mono) or the current (Parallel-Mono)

presented to the load. This feature gives the user flex-

ibility in maximizing the power available to the load.

A wide-bandwidth multiloop design is used for state-

of-the-art compensation. This produces ideal behav-

ior, and results in ultra-low distortion values.

Aluminum extrusions have been widely used for heat

sinks in power amplifiers due to their low cost and rea-

sonable performance. However, measured on a watts

per pound or watts per volume basis, the extrusion

technology doesn’t perform nearly as well as the heat

sink technology developed for

Macro-Tech

power am-

plifiers.

Our heat sinks are fabricated from custom convoluted

fin stock that provides an extremely high ratio of area

to volume, or area to weight. All power devices are

mounted directly to massive heat spreaders that are

electrically alive. Electrifying the heat spreaders im-

proves thermal performance by eliminating the insulat-

ing interface underneath the power devices. The

chassis itself is used as part of the thermal circuit, and

this maximizes utilization of the available resources.

5.2 VZ Power

means Variable Impedance. It is the name of

Crown’s patented articulated power supply technology.

This technology is what makes it possible to pack such

tremendous power into Crown’s

Macro-Tech 3600VZ

and

5000VZ

amplifiers.

5.2.1 Background

A power supply must be large enough to handle the

maximum voltage and current necessary for the ampli-

fier to drive its rated power into a specified load. In the

process of fulfilling this requirement, conventional

power supply designs produce lots of heat, are heavy,

and take up precious real estate. And it is no secret

that heat is one of a power amplifiers worst enemies.

Consider the circuit in Figure 5.1.

According to Ohm’s Law, the bigger the power supply,

the more heat the power transistors must dissipate.

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