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
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