FOUR CHANNEL
POWER AMPLIFIER
1200C
FEATURES
◆
4x370 W into 8
Ω
4x380 W into 4
Ω
at clip level with four
channels driven
◆
Compact design, 2 U high
(88 mm)
◆
Low weight
◆
MLS switch offers full power
in 8 or 4 ohms without
increased power losses
◆
Electronically balanced
inputs
◆
LED indicators show output
voltage and headroom
◆
Independent protection
circuitry
◆
ALS
TM
short circuit protection
manages long-term short-
circuit operations
◆
VHF protection
◆
DC protection
◆
Output cooled by Intercooler
®
◆
Two proportional speed fans
◆
Clip limiter
LAB. GRUPPEN’s LAB 1200C is a four-
channel, 370 watts per channel,
light-weight power amplifier,
designed for 19” rack mounting.
T
he LAB 1200C gives the opportunity
of use in several applications, such as; in
multi-channel monitor systems, four-
channel reproduction, and compact am-
plification in active 2-, 3-, and 4-way
systems.
The LAB 1200C gives the possibility
to bridge connect one or two of the two
pair of channels (channel A and B and/
or channel C and D). These bridge
mode combinations solve most of the
problems concerning different imped-
ance’s and maximum power handing of
loudspeakers.
The switch-mode power supply is the
modern solution of the weight and size
problem. With switch technology oper-
ating at a high frequency, it is possible to
use ferrite transformers instead of heavy
iron transformers and large electrolytic
capacitors.
Switch-mode technology has been ap-
plied in power supplies in TV-sets during
the latest 30 years. But in the LAB 1200C
the power capacitivity is 10 times larger.
We have designed the LAB 1200C to
obtain the same characteristics as a con-
ventional power supply. Thanks to the
switch-mode power supply it is easy to
get the DC-rail voltage stabilised. This is
made by controlling the magnetic ener-
gy in the ferrite transformer with a
pulse width processor and magnetic
“Flux Sense” windings.
Twenty-four 250 watt bipolar power
transistors constitute the output stages,
which are totally complimentary. The
power transistors are cooled by a solid
copper cooler, called Intercooler®, origi-
nally designed for our LAB 1300 power
amplifier. LAB. GRUPPEN’s specially
designed thermal feedback circuit pro-
tects against thermal breakdown.
The LAB 1200C is completely short-
circuit protected . The LAB 1200C is
equipped with LAB. GRUPPEN’s Adap-
tive Limiting SystemTM short circuit
protection, which permits very high
peak-currents, but still holds the transis-
tors within the so-called “Safe Opera-
tion Area” at the present operating volt-
age. This makes it possible to run
loudspeakers with impedance varia-
tions, which are considerably lower than
the lowest permitted impedance of the
power amplifier.
Six more protection circuits, which
are separate for each channel, protect
the LAB 1200C and the loudspeakers:
Two DC protections; one DC current
limitation protection, supplemented
with fuses on each DC voltage power
supply rail; and one DC voltage protec-
tion of Crowbar type, which works by
short-circuiting the output to protect
the load.
Thermal protection; prevents the
LAB 1200C from being overheated. The
protection indicators on the front panel
are switched on, as a warning, before the
protection occurs.
VHF protection (Very High Frequen-
cy); protects the loudspeakers against
strong non-musical signals above the
audible area.
Clip limiter; prevents severely clipped
waveforms from reaching the loud-
speakers, but maintains full peak power.
AC protection; shuts down the out-
puts if the line voltage is outside the
operating voltage of the LAB 1200C.
All electronics are mounted on six
modules. The modules are easily accessi-
ble for replacement or repair, etc.