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Macro-Tech 5000VZ Power Amplifier
Reference Manual
5 Technical Information
5.1 Overview
Your
Macro-Tech VZ amplifier incorporates several new
technological advancements including low-stress out-
put stages, real-time simulation of output transistor con-
ditions, advanced thermal management, a modular
system for signal input and processing, multispeed
compressors, Loudspeaker Offset Integration, split
feedback paths, modular internal construction and ar-
ticulated
VZ 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 or
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 supplies, ex-
cessive temperature, chain-destruction phenomena,
input-overload damage and high-frequency blowups.
The unit protects loudspeakers from DC in the input
signal, output DC in the output, and turn-on/turn-off
transients. The amplifier is also protected from internal
faults.
The four-quadrant topology used in the grounded out-
put 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 output de-
vices 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 de-
vices are constructed to function as gigantic NPN and
PNP devices. Each output stage has two composite
NPN devices 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 synchronously.
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 behavior
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 amplifiers.
The heat sinks for the
Macro-Tech 5000VZ are fabri-
cated from custom milled fin stock that provides an ex-
ceptionally high ratio of area to volume, or area to
weight. All power devices are mounted directly to mas-
sive heat spreaders that are electrically at the Vcc po-
tential. Electrifying the heat spreaders improves
thermal performance by eliminating the insulating in-
terface underneath the power devices. The chassis it-
self is even used as part of the thermal circuit to
maximize utilization of the available resources.
5.2 VZ Power
VZ 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
VZ 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’s no secret that
heat is one of a power amplifiers worst enemies. Con-
sider the circuit in Figure 5.1.
According to Ohm’s Law, the higher the power supply
voltage, the more heat the power transistors must dis-
