Crown Audio CH Series Operation, CH and CL Series Power Amplifiers, page, Indicators, Controls

CH and CL Series Power Amplifiers

3 Operation

3.2 Indicators

The front panel of a Contractor Series amplifier has several helpful indicators (Figure 3.6). The blue Power indicator shows that the amplifier has been turned on and has power.

		POWER
CLIP	FAULT	FAULT	CLIP
SIGNAL			SIGNAL

Figure 3.6 Indicators

The red Fault indicators blink under five dif- ferent conditions:

1. When the amplifier is first powered up, until the unit is ready for operation.

2. If the heatsinks reach a temperature above normal working limits. This can be caused by any number of abnormal conditions including but not limited to extremely low load imped- ance and/or inadequate cooling (see Section 1 for more information on cooling).

3. If the transformer (high-voltage power sup- ply) thermal protection circuit is activated. Higher than rated output levels, excessively low-impedance loads and unreasonably high input signals can generate more heat in the power supply than in the output devices. This can overheat the power supply and activate the Fault protection circuit.

4. If amplifier output wires develop a short-cir- cuit. This could be caused by a short anywhere along the circuit from the output connectors to the speakers, including shorted speaker driv- ers.

5. If the amplifier output stage stops operating.

The red Clip indicators turn on when distor- tion is audible in the amplifier output.

The green Signal Presence Indicators (SPI) illuminate when a signal (>–40 dBm) is present at the INPUT of the amplifier. This indi- cator is before the level control, so it can be used to troubleshoot wiring problems within a system. If the indicators are not lit, signal is not reaching the amplifier.

3.3 Controls

The Enable switch is located on the front panel so you can easily turn the amplifier on and off.

A 21-position Detented Level Control is provided for each channel. Level attenuation may be adjusted in steps. For security, the level controls are located on the back panel.

A two-position Mode switch, located on the back panel, allows the selection of either Stereo or Bridge mode of operation.

Stereo mode provides identical power output to each of the two amplifier output channels. Bridge mode combines the two amplifier output channels into a single mono channel with twice the voltage of a single stereo channel. It does this by bridging the outputs, and it requires special output wiring. Do NOT select Bridge mode without first making sure the amplifier has been wired in a Bridge- Mono configuration. For more information on wiring for Bridge mode, see the Setup sec- tion of this manual (Section 2), or consult your system installer.

When Bridge mode is selected, only the Chan- nel 1 Level control and the Channel 1 Signal indicator will work. If the Channel 2 input is wired, the Channel 2 Level Control should be turned all the way down (counter/anti-clock- wise) to prevent distortion.

A two-positionOutput Operation switch (CH Series amplifiers only) allows the selection of either 4/8 ohm or 70V output from the ampli- fier. See Section 2 for more information about output operating modes.

Fault Jack: This RJ11 jack (which looks like a phone jack) is located on the back panel. By attaching a signalling device to the Fault jack, you can monitor the amplifier’s Fault status from a remote location. See Section 4.3.3 for more information on fault monitoring and sug- gestions for signalling device circuity.

A circuit breaker is provided to prevent the high-voltage power supplies from drawing excessive current. A Reset switch for the cir- cuit breaker is provided on the back panel. If the circuit breaker trips, the Power indicator turns off. In this situation, turn off the Power switch and reset the circuit breaker. Then, turn the Power switch back on. If it trips again or the unit fails to operate properly, contact an autho- rized Crown Service Center or Crown Factory Service.

page 18 Operation Manual