Crown Audio Advanced Features and Options continued, MA-5002VZ Power Amplifier, page

MA-5002VZPower Amplifier

5 Advanced Features

and Options (continued)

The VZ Mode switches allow you to control the opera-	Note: When ODEP limiting begins, the IOC circuitry will
tion of the VZ power supply for each channel.	see that the input waveform does not match the output
The VZ mode switches are located inside the amplifier	waveform, and an error signal is generated. If the
	compressors are on, they will see the error signal and
behind the top dust filter on the front panel. To access
	compress the input signal to correct the problem. When
these switches, remove the top filter element. Always
	this happens, there is no audible signal degradation.
turn the power off before changing one of these
	Compression is subtle, and not noticeable unless the
switches. Each switch has four settings (from left to
	system is driven to extremely high levels.
right): VZ-ODEP, Lock Low, VZ and VZ. Note: The third
	The Lock Low mode locks the power supplies into the
and fourth positions are identical. The amplifier is shipped
from the factory with the switches set to "VZ-ODEP”.	high-current mode for low-impedance loads. This may be
The VZ (Variable Impedance) mode causes the power	desirable when driving high-frequency transducers that
	must be protected from too much voltage, or when driving
supplies to automatically shift between high-current and
	loads with very low impedances.
low-current modes of operation as operating conditions
change. Normally, the power supplies operate in the high-	5.2.3 ILoad/ILimit
current (low-impedance) mode for maximum thermal effi-
	The ILoad/ILimit feature is designed to help you get the
ciency. When voltage demand reaches highs levels, the
	maximum power out of your amplifier. In the real world,
supplies quickly shift into high-voltage (high-impedance)
	loudspeaker impedance varies with frequency, and loud-
mode. Because voltage and current requirements vary with
	speaker impedance ratings are only approximations. With-
the output level and frequency content of the source
	out ILoad/ILimit, you have to do some lengthy calculations
signals, the power supplies are designed to be able to
	to approximate the maximum number of loudspeakers you
continually switch between the two modes as needed with
	can drive with the amplifier—and this does not allow for a
no degradation to the audio signal.
	4 ohm loudspeaker whose impedance drops below 2 ohms
The VZ-ODEP mode is very similar to VZ mode. The	at 80 Hz.
only difference is that the power supplies are forced into	This is why your amplifier has ILoad/ILimit. The ILoad
high-current mode when ODEP is close to activating its
	function turns a channel’s ILoad/ILimit indicator green
limiting circuitry. This reduces excessive stress on the
	when it senses current is flowing to the load. The ILimit
output transistors, and effectively increases the thermal
	function turns the indicator red when it reaches maximum
performance of the amplifier.
	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.
	Figure 5.1 Channel 1 VZ Mode Switch (Behind Filter)

5.2.4 Loudspeaker Offset Integration

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.

5.3 Options

5.3.1 PIP™ Modules

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.

page 16 Operation Manual