Crown 1160ma Guía Del Usuario

normally runs at very low speed when the 
amplifier is idling or when it is being used for 
low to moderate duty work. If the amplifier is 
delivering large amounts of power into low 
impedance loads, the heatsinks or transformer 
may heat up enough to increase the speed of 
the fan to medium and possibly to high speed. 
If the temperature continues to increase, the 
TLC circuit uses the compressor to reduce the 
gain of the input stage and thus reduce the 
power dissipated by the amplifier. As a further 
protective measure, if the temperature contin-
ues to rise (due to blocked airflow for example), 
the amplifier will stop running and keep the fan 
on high speed to quickly bring the temperature 
back to an operational level.

If a signal presented at the input of the amplifier 
will not be passed through to the output, the 
Fault LED will blink to get your attention. The 
turn-on delay, for example, will cause each 
channel’s LED to blink because the amplifier 
remains in standby for a few seconds before it 
allows audio output.

An RJ11 modular jack is mounted on the back 
panel. Pins 2 and 5 are connected to an opto-
isolator that is always in a low-resistance state 
whenever the unit is on and happy. Should a 
fault be detected or should the amplifier 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 to the ampli-
fier front end.

The Clip indicators are driven from the output 
of the compressor circuitry and light to indicate 
the onset of audible distortion. The Power indi-
cator LED is driven from the low-voltage sup-
ply.

AC power enters the amplifier through a power 
cord equipped with an IEC (unplugable) con-
nector. It then is passed through the EMI filter. 
Circuits that use switching technology will nor-
mally send a small amount of high-frequency 
noise back down the power cord and into the 
power distribution system. This noise must be 
removed in order to sell the unit in certain parts 
of the world. Since the CH4/CL4 is a worldwide 
product, the EMI filter removes this noise so 
that it does not exit the box.

The power then enters the Power Factor Cor-
rection (PFC) Boost stage. This stage is what 
allows the CH4/CL4 to be plugged into any 
outlet in the world without any modifications to 
the amplifier. The PFC stage uses switching 
power supply technology to take whatever AC 
line voltage comes in, convert it to DC and 
boost it to 400 Volts. The circuit also uses 
intelligence to draw the current from the line 
sinusoidally and in phase with the line voltage. 
This reduces the load on the power companies 
and also allows the amplifier to pull more peak 
power from the power source (the outlet). The 
power is drawn in small amounts 62,500 times 
each second and is used to provide power to 
the isolation stage and to fill the large energy 
reservoir capacitors.

The power then goes to the “buck” isolation 
stage. This stage takes the 400 Volt PFC volt-
age and, again using switching power supply 
technology, converts it down (“bucks” it down) 
to the level needed to power the audio output 
stage. The isolation stage also satisfies a safety 
requirement by providing isolation, using a 
transformer, between the AC mains power and 
the power that is delivered to the speakers. The 
isolation stage moves power 125,000 times 
each second from the primary to the secondary 
to power the audio output stage and keep its 
large energy reservoir capacitors full.

In order to keep the power supply controllers, 
protection circuits, and the audio signal path 
components powered, another switching power 
supply is used, this one also running at 125 
kHz. This one is also a “buck” type supply in 
that it takes voltage from the 400 Volt PFC bus 
and converts it down to the low voltages 
needed. This circuit also uses a transformer to 
provide safety isolation.

Like the audio signal path parts of the amplifier, 
there are many ways that the power supply pro-
tects itself. Part of the start-up time delay men-
tioned above occurs while the power supply is 
ramping up all of its voltages (soft-start) so that 
large inrush currents are avoided. Current lim-
iters and over-current detectors are used to 
protect the power supply output devices. The 
power supply will also detect severe brownouts 
and shut off the supply until the brown-out is 
over if the line voltage is drastically less than 
normal.