Interfire Audio A900.4 - Manual (Page 12)

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1.Set to the "H.P.F" position when the amplifier is used to drive a tweeter/midrange system.
The frequencies below the crossover point will be attenuated at 12dB/octave. Permits
adjustment of the crossover frequency ,by rotating the knob to select any frequency
2.Set to the "L.P.F" position when the amplifier is used to drive a subwoofer. The frequencies
above the crossover point will be attenuated at 12dB /octave. Permits adjustment of the
crossover frequency, by rotating the knob to select any frequency between 50Hz to 250Hz
3.Set to the "OFF" position when the amplifier will be used for driving full-range speakers.
The full frequency band width (20Hz - 20kHz) will be output to the speakers without high
4.Level adjustment-The sensitivity adjustment is to allow the amplifier to work with many
different brands of head units. It allows input signal to vary between 350 millivolts to 5
volt from the head unit or other signal processor. Start by setting the sensitivity adjustment
to the "MIN" (3 volts).Using a cassette or compact disc that you are familiar with ,turn on
head unit to the 3/4 volume setting. Slowly turn up sensitivity adjustment towards the
"MAX" (200 millivolts) using a flat head screw driver. Stop turning on the onset of distortion
and turn back just a slight. The 3/4 volume setting is now the "maximum" volume for the
head unit. The goal is to keep the level control to the lowest setting yet still have enough
signal to drive the amplifier. This is done to prevent over driving the amplifier and to keep
system noise to a minimum. It is important not over drive speakers (at point of distortion)
this will cause permanent damage to the speakers. Also, if the amplifier itself is over driven,
5.The "BASS" function can be selected to increase low frequency response output, or
decrease frequency response output. The "BASS" function will be working at only "OFF"
between 80Hz to 1.2kHz & 50Hz to 500Hz as the crossover point.
& 50HZ to 500Hz as the crossover point.
or low frequency attenuation.
it could be damaged.
or "L.P.F" position.
• The BASS is adjustable from 0 ~ 12dB boost at 50Hz.