Crown Audio MA-5002VZ User Manual

The VZ Mode switches allow you to control the opera-
tion of the VZ power supply for each channel. 

The VZ mode switches are located inside the amplifier 
behind the top dust filter on the front panel. To access 
these switches, remove the top filter element. Always 
turn the power off before changing one of these 
switches. Each switch has four settings (from left to 
right): VZ-ODEP, Lock Low, VZ and VZ. Note: The third 
and fourth positions are identical. The amplifier is shipped 
from the factory with the switches set to "VZ-ODEP”.

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. 

The VZ-ODEP mode is very similar to VZ mode. The 
only difference is that the power supplies are forced into 
high-current mode when ODEP is close to activating its 
limiting circuitry. This reduces excessive stress on the 
output transistors, and effectively increases the thermal 
performance of the amplifier. 

Note: When ODEP limiting begins, the IOC circuitry will 
see that the input waveform does not match the output 
waveform, and an error signal is generated. If the 
compressors are on, they will see the error signal and 
compress the input signal to correct the problem. When 
this happens, there is no audible signal degradation. 
Compression is subtle, and not noticeable unless the 
system is driven to extremely high levels. 

The Lock Low mode locks the power supplies into the 
high-current mode for low-impedance loads. This may be 
desirable when driving high-frequency transducers that 
must be protected from too much voltage, or when driving 
loads with very low impedances.

The ILoad/ILimit feature is designed to help you get the 
maximum power out of your amplifier. In the real world, 
loudspeaker impedance varies with frequency, and loud-
speaker impedance ratings are only approximations. With-
out ILoad/ILimit, you have to do some lengthy calculations 
to approximate the maximum number of loudspeakers you 
can drive with the amplifier—and this does not allow for a 
4 ohm loudspeaker whose impedance drops below 2 ohms 
at 80 Hz.

This is why your amplifier has ILoad/ILimit. The ILoad 
function turns a channel’s ILoad/ILimit indicator green 
when it senses current is flowing to the load. The ILimit 
function turns the indicator red when it reaches maximum 
current output. This makes it possible to connect real 
loudspeakers and conduct realistic tests to find the maxi-
mum number of loudspeakers that should be connected. 
To do a test like this, you can operate under worst-case 
conditions and continue to connect additional loudspeak-
ers in parallel with each output until the ILoad/ILimit indi-
cator turns red. The optimum load is achieved before the 
ILoad/ILimit indicator turns red, so disconnecting the last 
added loudspeaker gives you an optimized load.

Loudspeaker Offset Integration (LOI) circuits use double 
integrating filters in the amplifier’s feedback circuitry to 
protect loudspeakers in several different ways. First, they 
center asymmetrical audio waveforms that cause off-center 
woofer cone movement. Off-center cone movement 
increases loudspeaker heating and distortion while reduc-
ing the loudspeaker’s power handling ability. Second, LOI 
filters unwanted DC and subsonic frequencies using a 
third-order Butterworth filter with a 35 Hz corner 
frequency. Third, LOI filters unwanted ultrasonic frequen-
cies (RF) that can cause tweeter burnout using a second-
order Bessel filter with a 50 kHz corner frequency.

IMPORTANT: The Loudspeaker Offset Integration 
circuitry does NOT protect loudspeakers from 
large transient voltages or excessive power 
levels for prolonged periods of time. Crown is not 
liable for damage or personal injury that results from over-
driving loudspeakers or other system components. For 
information on techniques to protect loudspeakers, refer to 
the Crown Amplifier Application Guide, available online at 
www.crownaudio.com.

Versatile PIP (Programmable Input Processor) modules 
provide flexible expansion features that can be added to 
customize the amplifier. PIP modules plug into the 
connector inside the back panel of the amplifier. PIP 
modules are available with features ranging from error-
driven compressor/limiters to .remote control and moni-
toring via System Architect or IQwic™. Your amplifier is a 
PIP2 

 

amplifier, which means it can take advantage of the 

many advanced features found in PIP2 modules, as well as 
all standard PIP modules. Visit the Crown website at 
www.crownaudio.com, or contact Crown Customer 
Service, for descriptions of available PIP and PIP2 
modules.