10
3
Thermal Protection
The thermal protection system ensures the amplyfier
’
s reliable and faultless operation
in case of overheating. The fan is completely OFF until the temperature of the heat sink
reaches 50
°
Ñ
. When the heat sink temperature exceeds 50°
Ñ
, the cooling fan goes ON at
its least speed. Any further rise of temperature results in a smooth increase of the cooling
intensity rate up to 70
°
Ñ
. At the same time, when the temperature rises to 65°
Ñ
, the built-
in optoelectronic Clip-limiter becomes active reducing the input signal level on the amplifier
input without distorting the sound. In this case, the thermal protection LED becomes slightly
lit (dim). The higher the temperature, the lower signal level, the brighter is the LED.
The signal may be cut off only in case of the fan breakdown or blocked air flow. If this
is the case, the thermal protection system disables the input signal when the heat sink
temperature has reached 85
°
Ñ
, this state being indicated by the CLIP/THERM LED.
The amplifier resumes its operation in the reverse order as soon as has cooled down,
gradually regaining its amplification level up to the set value.
Soft Signal Start
This feature ensures smooth signal volume increase on power-on and on resumption
of operation of the unit after an alarm condition to avoid any undesirable impact on the
loudspeakers.
Indication
The indication consists of two LEDs, one of which indicates the power on condition, and
the other the overload condition and thermal protection active condition.
Input Section
The input section incorporates:
–
two line input (XLR female);
–
two line output (XLR male);
–
low-pass filter control knob;
–
output signal phase slide switch.
The amplifier inputs are balanced.
The line input and output connectors are parallel, i.e. the contacts of the output
connector match the respective contacts of the input connector. This allows to use the
amplifier as a signal patching unit (e.g. for supplying the signal to active satellite speaker
systems), while the unit itself amplifies the summed signal taken from both inputs.
The level control knob is used to adjust the level of the signal supplied to the amplifier.
The low-pass filter control knob allows to set the upper frequency limit of the amplifier
bandwidth (between 80 Hz and 350 Hz).
The output signal phase slide switch is provided for 180
° reversing of the signal phase
in order to achieve the best compatibility of the sound signal phase of the subwoofer (in which
this amplifier is installed) with other loudspeakers within the same sound reproduction
system.
TROUBLESHOOTING
No Sound Signal on the Output
POWER LED is OFF:
–
power cable is damaged;
–
no power.
POWER LED is ON while CLIP/THERM LED is OFF:
–
no input signal;
–
input level knobs are set to minimum position.
POWER and CLIP/THERM LEDs are ON:
–
load impedance is too low, or short-circuited load;
–
active overheating protection.
The problem may be caused by the input signal source. Try disconnecting the input
signal and check the result.
Sound Distortion
–
applied input signal is distorted before it gets to the amplifier;
–
high input signal;
–
speakers are damaged.
