Advanced Features And Options; Protection Systems; Thermal Level Control (Tlc); Junction Temperature Simulation (Jts) - Crown CTs 1200 Operation Manual

5 Advanced Features
and Options
NOTE: For detailed information about
these Crown amplifi er features, please
consult the Crown Amplifi er Application
Guide, available on the Crown website
at www.crownaudio.com

5.1 Protection Systems

Your Crown amplifi er provides extensive
pro tection and diagnostic capabilities,
including thermal level control, fault indicators,
high-pass fi ltering, DC protect, AC under/over
volt age protection, inrush limiting, and

variable-speed fans.

5.1.1 Thermal Level Control (TLC)

If the amplifi er becomes too hot for safe
opera tion, the light will shine brightly and TLC
will engage the input compressor. By
compressing the input, the amplifi er will not
generate as much heat and will have a chance to
cool down. The degree of compression is
proportional to the amount of overheating. This
feature allows the show to go on, rather than
having the amplifi er shut down.
5.1.2 Junction Temperature
Simu lation (JTS) (CTs 600/1200
only)
JTS circuitry simulates the operation of the
amplifi er's output transistors, and compares it
against the transistors known Safe Operation
Area (SOA). If JTS sees that more power is
about to be asked of the output devices than
they are capable of delivering under the present
conditions, JTS immediately limits the drive
level until it falls within the SOA. Limiting is
proportional and kept to an absolute minimum-
only what is required to prevent the possibility
of output transistor damage.
This level of protection enables Crown to
increase output transistor utilization while also
greatly increasing amplifi er reliability.
page 18

5.1.3 Fault

The amplifi er will light the Fault LED if the
amplifi er output stage stops operating. If this
happens, see Section 8 for servicing
informa tion.

5.1.4 High-Pass Filters

Very low frequency signals contain no useful
musical energy, waste valuable amplifi er power
and headroom, and can be damaging to your
speakers. Your Crown amplifi er provides high-
pass fi lters to remove these signals from each
channel's output.
On the back panel are two 3-position 3rd-order
high-pass fi lter switches (one per channel) with
selections of Off, 35Hz and 70 Hz.

5.1.5 Low-Pass Filters

Gaussian-approximation ultrasonic fi lters
pre vent ultrasonic feedback and HF burnout in
drivers. This type of fi lter preserves transient
response better than a Butterworth fi lter.
5.1.6 AC Under/Over Voltage
Protection
If the AC line voltage drops below 25% or rises
above 15% of the nominal operating voltage of
the amplifi er, the amplifi er's power supply turns
off and the blue Power LED fl ashes. The
ampli fi er will turn back on when the AC line
voltage returns to safe operating levels (within
+15% / -25%).

5.1.7 Circuit Breaker

A circuit breaker located near the IEC power
inlet protects the amplifi er from excessive AC
current draw.

5.1.8 DC Output Servo

The output servo circuit protects your drivers by
eliminating DC offset, even in the presence of
very large asymmetrical signals.
CTs Power Amplifi ers

5.1.9 Inrush Limiting

A soft-start circuit in the power supply
mini mizes the amplifi er's current draw during
power-on.
5.1.10 Variable-speed Fans
Two continuously variable speed fans direct the
airfl ow through the amplifi er for cooling.
5.2 Advanced Features

5.2.1 Switching Power Supply

Crown's Switching Power Supply minimizes the
amplifi er's weight.
Typical non-switching power supplies require
large, heavy transformers in order to produce
the required power at the output stage. These
transformers must be large to operate at 50 to
60 Hz (standard AC supplied by the power
company).
By contrast, switching power supplies can
operate with a much smaller (and lighter)
trans former because they fi rst convert the AC up
to a much higher frequency, thereby reducing
waste.
The power supply is voltage-specifi c, allowing
use in regions using 120V or 240V.

5.2.2 Input Compressor

Prevent input/output overload.

5.2.3 Sleep Circuit

Lowers standby power consumption by shut ting
down the high-voltage supplies during idle
periods.
NOTE: By default, the sleep circuit is not active
on the CTs 600/1200, but may be activated as a
service option.
Operation Manual