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Input Level control
The input level control, 5V – 0,25 V,
matches the output of your radio to
the input of the amplifier. After instal-
lation is complete, make sure the in-
put of the amplifier is turned down all
the way ( counter-clockwise at 5V ).
Play a tape or CD, make sure all bass or treble
settings or equalizer are flat, and turn the volume of
the radio up until you just start to hear distortion.
Turn the volume control down just a bit. On the
amplifier increase the input level control ( clockwise
or to the right ) until you just start to hear distortion,
then back the level control just a bit. Now your radio
and amplifier levels are matched.
Phase control MRA31
The phase control on MRA31
continuously from 0 - 180 degrees. This is very
useful when you want to adjust the bass sound for
best front stage image. Start on 0 and turn the control
slowly clockwise until you experience that the bass
sound is coming from the front. If you dont get the
result you want, also try to
phase reverse the subwoofer
connections and make
a new adjustment.
NOTE: This function is intended for car use and
may not be fully functional in boats. Set the control
to 0.
Crossovers
Both amplifiers include high pass filter
( HPF ) and low pass filters ( LPF).
All filters are continously variable and all filters can
be switched on and off. MRA31 also include a
subsonic filter.
High Pass Filter (HPF)
Level
5V
0,25V
Off On
The HPF (high pass filter) blocks very low
frequencies from reaching the speakers. It is mostly
used at say 60 Hz to protect small speakers (like 6
inch and smaller) from deep bass. It can also be
used as subsonic filter to take away the very
deepest frequencies from a bass box. The typical
setting is then around 25 – 40 Hz.
The filter can be switched off if you want to run the
amplifier in full range mode.
can be set
Low Pass Filter (LPF)
PHASE
Off On
The LPF (low pass filter) mostly used for
0
180
subwoofers. It will allow low frequencies only and
blocks higher frequencies. A typical setting is 50 –
80 Hz. The filter can be switched in and out.
Subsonic filter MRA31
The Subsonic filter blocks the very
deepest frequencies from reaching the
subwoofers. It has a fixed frequency
of 25 Hz and can be switched On / Off.
For sub channel C only.
MRA22, MRA31
HPF
50Hz 220Hz
Filter freq. range:
MRA22: 15-150 Hz
15Hz 500Hz
MRA31: 50 - 150 Hz
LPF
80Hz 200Hz
Filter freq. range:
MRA22: 50-500 Hz
50Hz 500Hz
MRA31: 50 - 120 Hz
Subsonic
Off On
5
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