Crown MARCO-TECH 5000VZ User Manual

Notes
MACRO-TECH 5000VZ
OVERVIEW
At first glance the MA-5000VZ looks a great deal Hke any other MA
Series amplifier, except that ¡t is physically larger and puts out more
power. The internal structure of the MA-5000VZ is, however, quite
different from other models in the MA une. To the user, this one is like
the others, but with a f ew more f eatures. To the technician, this amplifier
representsaradicaldeparturefromthe"normal"Crowndesign. Previous
chapters covered the "normal," this chapter shall endeavorto take the
MA-5000VZ as a unique entrty.
The amplifier ¡s protected from all common hazards that plague high-
power amplifiers, including shorted, open or mismatched loads,
overloaded power supplies, excessive temperature, chain-destruction
phenomena, input-overload damage, and high-frequency blowups.
The unit protects loudspeakers from DC in the input signal and from
turn-on and turn-off transients. It also detects and prevenís unwanted
DC on the outputs. Additional protection features include input current
sense, overvoltage (AC mains).
A mode of protection which may be switched on or off is called
Loudspeaker Offset Integration (LOI). The LOI circuit, when switched
on, prevenís excessive bass frequency cone excursions below the
audible frequency range. It operates essentially as a band-pass filter.
The low frequencies are rolled off at 18dB/oclave with a -3dB córner of
35 Hz (Butterworth response). Ullra-sonics are rolled off wilh a second
order Bessel response and -3dB córner of SOkHz.
A compression circuil in each channel may be switched off, on slow, or
on fast by swilches on Ihe rear panel. This compressor is aclivaled by
eilherinputoverloadord¡stort¡on(cl¡pping). Compression ratio is infinite
(operates as a peak limiter).
Thefour-quadrant lopology used in the grounded oulpul slages is called
Ihe grounded bridge and makes full use of Ihe power supplies. This
patentad lopology also makes peak-lo-peak voltages available lo the
load which are twice the vollage any output device ¡s ever exposed to.
The grounded bridge is covered in detail in the BASICS seclion of this
texl.
MA-5000VZ - 1