Therefore, whenever this indicator is in red, will indicate us that the power amplifier
input signal is disconnected, and the power amplifier is not operative at that moment. This
occurs when the power amplifier is turned on, and when the ERROR or THERMAL protections
are activated.
The power amplifier has two ON/STBY LED
indicators, one per channel.
POWER SWITCH
The power switch of the models MF16 and MF24 has a thermal breaker
inside. This thermal breaker acts interrupting the mains supply of the power
amplifier, when the mains current is high or equal to 20 amperes. When the
thermal breaker work, the power switch is placed in the OFF position, for what it is
necessary to turn on the power amplifier in order to use it again. It is important to
know what circumstance happen and correct this, before power up the power amplifier
again.
The models MF8 and MF12 incorporates power switches without thermal
breaker.
FAN
The power amplifier includes a thermally controlled system, which continuously regu-
lates the fan speed depending on, the heat energy it has to evacuate. This variable speed
circuit, avoids abrupt changes of temperature and substantially extents the working life of the
components builds in. At power amplifier turn on, the fan rotates with his top velocity, in
order to exhaust the maximum dust possible. Soon after, the fan's speed drops to normal.
The power amplifier fan rotates with its top velocity also, in an overheating situation (when a
thermal protection work) so that the heat drops under the security level quickly.
In the models MF16 and MF24, the fan is protected with a grid, that avoids objects
inserted between its wheels, as well as a possible accident with the same. It is important that
nothing obstruct the airflow to the fan at any time.
The models MF8 and MF12 have the fan inside, for what doesn't have protection grid,
however incorporates some cooling vents in the rear panel for which the air is evacuated, for
what it is important make sure that the cooling vents are always free so that the air could
circulate with freedom.
LOAD IMPEDANCES
The power amplifiers MF series, are designed to drive a 2
Ω
or higher load impedances
load in MONO or STEREO mode (4
Ω
or higher in mode BRIDGE), without current limiting.
However, using several speakers in parallel in order to get these 2
Ω
it could be an imped-
ance of load of less than 2
Ω
.
The speaker load impedance is variable with the frequency, and in fact, connect four
speakers in parallel, with a nominal impedance of 8
Ω
each one, gives a less impedance like
result that the theoretical 2
Ω
. Therefore high signal levels associated with a compressed
signal source can cause the power amplifier to reach its thermal limits and disconnects its
load.
ALTAiR
PROFESSIONAL POWER AMPLIFIERS MF SERIES
17
