Crown Audio MA-5002VZ ユーザーズマニュアル

Your Crown amplifier provides extensive protection and 
diagnostic capabilities, including ODEP and IOC. 

Crown invented ODEP to solve two long standing prob-
lems in amplifier design: To prevent amplifier shutdown 
during demanding operation and to increase the efficiency 
of output circuitry.

To do this, Crown established a rigorous program to 
measure the safe operating area (SOA) of each output tran-
sistor before installing it in an amplifier. Crown also 
designed intelligent circuitry to simulate the instantaneous 
operating conditions of those output transistors. Its name 
describes what it does: Output Device Emulation Protec-
tion or ODEP. It not only simulates the operation of the 
output transistors but it also compares their operation to 
their known SOA. If ODEP sees that more power is about to 
be asked of the output devices than they are capable of 
delivering under the present conditions, ODEP immedi-
ately limits the drive level until it falls within the SOA. 
Limiting is proportional and kept to an absolute mini-
mum—only what is required to prevent the possibility of 
output transistor damage.

This level of protection enables Crown to increase output 
transistor utilization while greatly increasing amplifier reli-
ability.

Finally, this onboard intelligence is monitored in two ways. 
First, the front panel ODEP indicators show whether the 
amplifier is functioning correctly or if ODEP is limiting the 
drive level. Second, ODEP data is fed to the PIP connector 
at the back of the amplifier so advanced PIP modules like 
the IQ-PIP-USP3 can use it to make decisions and control 
the amplifier.

With ODEP you get the maximum power with the maxi-
mum protection—the show goes on!

The IOC circuit compares the output signal of the amplifier 
with the input signal. If there is any difference other than 
gain, then it is considered distortion and the indicator 
comes on. The LED indicator will come on whenever there 
is distortion of 0.05% or more. An IOC condition may also 
be sensed by an IQ PIP module installed in PIP-compati-
ble amplifiers.

IOC is designed to report any form of distortion. IOC not 
only checks the waveform for distortion, but also reports 
input overload and even a protective action that mutes or 
shuts down an amplifier. With all of these features, IOC 
monitors the entire amplifier. When the IOC indicator is off 
the amplifier is definitely operational and undistorted. IOC 
provides an on-line proof of performance. 

Grounded Bridge is the name of Crown's unique four-
quadrant amplifier topology. The Grounded Bridge topol-
ogy takes full advantage of the power supplies delivering 
peak-to-peak voltages to the load that are twice the voltage 
seen by the output devices and twice the voltage generated 
by the power supplies.

The power supply bridge rectifier is not ground referenced, 
and the transformer secondary is not center-tapped. This 
allows the power supply to deliver +VCC and -VCC from 
the same bridge rectifier and filter as a total difference in 
potential regardless of their voltages with respect to 
ground.

Composite output devices are arranged to function as 
gigantic NPN and PNP devices. Each output stage has two 
composite 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 simulta-
neously in the high-side NPN and low-side PNP stage, 
while decreasing conductance of the high-side PNP and 
low-side NPN in synchrony.

Crown's Grounded Bridge design delivers large voltage 
swings without stressing output transistors. The results 
are higher efficiency, lower distortion and superior reliab-
lility.

VZ is the name of Crown's patented articulated power 
supply technology. This innovative technology permits us 
to pack large amounts of power into a compact package 
while achieving ultra-low distortion and without generat-
ing excessive heat.

An amplifier power supply must be large enough to handle 
both the maximum voltage and maximum current necesary 
for the amplifier to drive its rated power into a specified 
load. In order to meet this requirement, most conventional 
supplies are heavy, large, and produce lots of heat. In 
contrast, the VZ supply gets more current AND voltage out 
of a smaller, lighter, and more efficient package by dynam-
ically adapting to both signal and load requirements in 
real-time. This provides the best power match to the 
widest range of loads. 

The VZ supply is divided into two segments. When the 
output stage requires high-voltage, the segments are 
arranged in series to deliver twice the voltage of a single 
segment. When the output stage requires high-current, the 
segments are arranged in parallel to deliver twice the 
current of a single segment. Sensing circuitry "watches" 
the voltage of the signal to determine when to switch VZ 
modes. The switching circuitry is designed to prevent 
audible switching distortion to yield the highest possible 
dynamic transfer function—you hear only the music and 
not the amplifier. 

With VZ, you get not only maximum power and safety, but 
you also get the best power matching to your load.

The VZ (Variable Impedance) mode causes the power 
supplies to automatically shift between high-current and 
low-current modes of operation as operating conditions 
change. Normally, the power supplies operate in the high-
current (low-impedance) mode for maximum thermal effi-
ciency. When voltage demand reaches highs levels, the 
supplies quickly shift into high-voltage (high-impedance) 
mode. Because voltage and current requirements vary with 
the output level and frequency content of the source 
signals, the power supplies are designed to be able to 
continually switch between the two modes as needed with 
no degradation to the audio signal.