Protection Systems; Thermal Level Control; Fault; Fault Isolation Topology (Fit) - Crown CTs 4200USP/CN Operation Manual

4 Advanced Features
(continued)
NOTE: For more information about these Crown
amplifi er features, please visit the Crown
web site at www.crownaudio.com.

4.2 Protection Systems

Your Crown amplifi er provides extensive protection and
diagnostic capabilities, including thermal level control,
fault indicators, automatic high-pass fi ltering, DC pro tect,
AC under-voltage and over-voltage protection, inrush
limiting, and variable-speed fans.
4.2.1 Thermal Level Control (TLC)
If an amplifi er channel starts to overheat, the TLC circuit
will engage that channel's input compressor. By
com pressing 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. If the channel becomes too hot for safe
operation even after full TLC limiting, the channel will
shut off, and the Thermal Indicator for that channel will
fl ash brightly to alert the user that a state of thermal stress
or overload has cause the channel to shut down.

4.2.2 Fault

If an amplifi er channel requires service, the correspond-
ing Fault indicator will illuminate to alert the user of this
condition. If this occurs, return the amplifi er to the Crown
factory or to an authorized Crown service center.

4.2.3 Fault Isolation Topology (FIT)

Crown's new FIT (Fault Isolation Topology) design
iso lates channel-specifi c faults, and prevents them from
affecting remaining channels. If a CTs multi-channel amp
is powering multiple zones, and a channel fails, the other
zones continue to operate. FIT makes the CTs 4200USP/
CN and CTs 8200USP/CN the most trustworthy multi-
channel amplifi ers in the business!
page 22
4.2.4 High-Pass Filter
A fi xed 35-Hz (70-Hz in CTs 4200USP/CN) high-pass
fi l ter per channel pair is automatically inserted when the
mode switch is set to either of the constant-voltage
set tings. The high-pass fi lter corner frequency can be set
to 70 Hz, or bypassed, with a service option.
4.2.5 AC Under-Voltage and Over-Voltage
Protection
If the AC line voltage varies out of an acceptable range,
the amplifi er's power supply turns off and the blue Power
LED fl ashes. The LED will continue to fl ash until the
power has been cycled. Figure 4.4 provides voltage lim its
for all amplifi er AC voltage confi gurations. Also, the
amplifi er must be run within the specifi ed mains
fre quency requirements (indicated on the amplifi er's back
panel label). If you are unsure of the output voltage of
your AC mains, consult your electrician.
Under-Voltage Over-Voltage
Models
Limit Limit
100VAC 90VAC 110VAC
120 VAC units 108VAC 132VAC
220V/230V/
198VAC 264VAC
240V units
Figure 4.4 AC Under-Voltage and
Over-Voltage Limits for Various Amplifi er
Models

4.2.6 Power Fuse

A fuse protects the amplifi er from excessive AC current
draw.

4.2.7 Inrush Limiting

A soft-start circuit in the power supply minimizes the
amplifi er's current draw during power-on.
CTs Multi-Channel Power Amplifi ers

4.2.8 Variable-speed Fans

Continuously variable speed fans direct the airfl ow
through the amplifi er for cooling.

4.2.9 Switching Power Supply

Crown's new 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 absorb the substantial waste that occurs when
operating 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) transformer 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/60Hz, 220V/50Hz, 230V/50Hz,
240V/50Hz, and 100V/50Hz AC mains.

4.2.10 Mode Switch

Each consecutive pair of channels has one four-position
switch that selects the amplifi er's mode of operation. The
switch positions are:
• Dual mode for 4 or 8 ohm operation.
• Dual mode for 70V constant-voltage operation.
• Bridge-Mono mode for 8 or 16 ohm operation.
• Bridge-Mono mode for 100V constant-voltage
oper ation.
Be sure to turn off the amplifi er before changing
the Mode-switch setting.

4.2.11 Bridge Mode Indicator

This yellow LED indicates when the amplifi er's mode
switch is set to the Bridge position. Each consecutive pair
of channels has one Bridge LED.
Operation Manual