Operation Manual; 5.1 Protection Systems; 5.1.2 Fault- Page 14

Operation Manual

CTs Multi-Channel 

Power Amplifiers

page 14

NOTE: For more information about these Crown 
amplifier features, please visit the Crown web-
site at www.crownaudio.com.

5.1 Protection Systems

Your Crown amplifier provides extensive protection and 
diagnostic capabilities, including thermal level control, 
fault indicators, automatic high-pass filtering, DC pro-
tect, AC under-/over-voltage protection, inrush limiting, 
and variable-speed fans.

5.1.1 Thermal Level Control (TLC)

If an amplifier channel starts to overheat, the TLC circuit 
will engage that channel’s input compressor. By com-
pressing the input, the amplifier 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 
flash brightly to alert the user that a state of thermal 
stress or overload has cause the channel to shut down.

5.1.2 Fault

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

5.1.3 Fault Isolation Topology (FIT)

Crown’s new FIT (Fault Isolation Topology) design iso-
lates channel-specific 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 4200 and 
CTs 8200 the most trustworthy multi-channel amplifiers 
in the business!

5.1.4 35-Hz High-Pass Filter

A fixed 35-Hz (70-Hz in CTs 4200) high-pass filter per 
channel pair is automatically inserted when the mode 
switch is set to either of the constant-voltage settings. 
The high-pass filter corner frequency can be set to 70 Hz, 
or bypassed, with a service option.

5.1.5 AC Under-/Over-Voltage
Protection

If the AC line voltage varies out of an acceptable range, 
the amplifier’s power supply turns off and the blue Power 
LED flashes. The amplifier will turn back on when the AC 
line voltage returns to safe operating levels. Figure 5.1 
provides voltage limits for all amplifier AC voltage con-
figurations. Also, the amplifier must be run within the 
specified mains frequency requirements (indicated on the 
amplifier’s back panel label). If you are unsure of the out-
put voltage of your AC mains, consult your electrician. 

5.1.6 Power Fuse

A fuse protects the amplifier from excessive AC current 
draw.

5.1.7 Inrush Limiting

A soft-start circuit in the power supply minimizes the 
amplifier’s current draw during power-on.

5.1.8 Variable-speed Fans

Continuously variable speed fans direct the airflow 
through the amplifier for cooling.

Models

Under-Voltage

Limit

Over-Voltage

Limit

100-120 VAC 

units

90VAC

132VAC

220V/230V/

240V units

198VAC

264VAC

5.2 Advanced Features

5.2.1 Switching Power Supply

Crown’s new Switching Power Supply minimizes the 
amplifier’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 first 
convert the AC up to a much higher frequency, thereby 
reducing waste. 

The power supply is voltage-specific, allowing use in 
regions using 120V/60Hz, 220V/50Hz, 230V/50Hz, 
240V/50Hz, and 100V/50Hz AC mains.

5.2.2 Mode Switch

Each consecutive pair of channels has one four-position 
switch that selects the amplifier’s mode of operation. The 
switch positions are:

•

Dual mode for 4 or 8 ohm operation.

•

Dual mode for 70V constant-voltage opera-

tion.

•

Bridge-Mono mode for 8 or 16 ohm opera-

tion.

•

Bridge-Mono mode for 100V constant-voltage 

operation.

Be sure to turn off the amplifier before changing 
the Mode-switch setting.

5.2.3 Bridge Mode Indicator

This yellow LED indicates when the amplifier’s mode 
switch is set to the Bridge position. Each consecutive pair 
of channels has one Bridge LED.

5 Advanced Features 
and Options

Figure 5.1 AC Under-Voltage and 

Over-Voltage Limits for Various Amplifier Models