Crown 1160ma Guía Del Usuario

switch is set to 4/8 Ohm, only the negative and 
4/8 ohm connections on the barrier block have 
audio present. This provides power to low 
impedance speakers. When the Channel Opera-
tion switch is set to 70V, only the negative and 
70V connections on the barrier block have 
audio present. This provides power to distrib-
uted speakers in a high-impedance “constant-
voltage” application.

The output relay, in conjunction with input sig-
nal mute circuit, assures a quiet turn-on and 
turn-off. In the event of an amplifier output fail-
ure, a triac will activate to turn off the offending 
channel to protect the speakers.

The turn-on delay circuit functions to keep the 
output relay open until all the voltages are up 
and stable, both in the amplifier, and in all the 
components in the system ahead of the ampli-
fier.

Heatsink temperature is monitored by a thermal 
probe attached to the heatsink. As the tempera-

ture rises, the probe sends a proportional cur-
rent to the proportional speed fan circuit which 
starts the fan. Should the power transformer 
reach its maximum safe temperature, an inter-
nal thermal switch opens and the fan circuit 
turns on full speed to quickly cool down the 
amplifier. It also disconnects the load via the 
output relay, removing any output current and 
further speeding a cool-down cycle. This point 
is set both to protect speakers and to guard 
against nuisance tripping.

Whenever the heatsinks or the transformer 
reach a maximum temperature, or during the 
normal turn on delay window, the front panel 
Fault Indicators will blink. 

An RJ11 modular jack is mounted on the back 
panel. Pins 2 and 5 are connected to an opto-
isolator which is always in a low-resistance 
state whenever the unit is on and operational. 
Should a fault be detected or should the ampli-
fier lose AC power, the opto-isolator will 

change to a high resistance, allowing the user 
to remotely detect the status of the amplifier.

The Signal Presence Indicators tap the signal 
chain just before the level controls and prior to 
the power amplifier chain. They are not ampli-
fier output indicators and should only be used 
to indicate the presence of signal at the ampli-
fier front end.

The Clip Indicator is driven from the output of 
the compressor circuitry and lights to indicate 
the onset of audible distortion.

The Power Indicator LED is driven from the 
low-voltage supply.

A positive and negative regulator form the ±15-
volt power supplies. Add to that the main trans-
former, a full-wave bridge rectifier, and high 
energy electrolytic to form the main power sup-
ply. They are protected by the front-panel line 
circuit breaker and controlled by the front-panel 
power switch.