Four.1i is a combination equalizer/line driver. The 1/2 DIN chassis can be
mounted in-dash, or under-dash using the included brackets.
Graphic EQ: The rotary knobs adjust the signal +/-12 dB at 125 Hz, 500
Hz, 2 kHz, and 8 kHz. There's a notch at each knob's center position so it's
easy to return to the flat setting.
Para-Bass: Para-Bass is a
single band, parametric equalizer for the bass output. Like the four graphic EQ
bands, the adjustment range is +/-12 dB; the center frequency is continuously
variable from 40 Hz to 80 Hz.
Line Driver: To achieve the
best possible signal to noise ratio and dynamic range from your amplifier, the
built-in line driver can increase the head unit's output voltage up to 20 dB (9.5 volts RMS/
13 volts peak).
Aux In: In addition to the
main input, there is an auxiliary input (stereo RCA). A switch on the front
panel toggles between the two inputs.
Volume: If you choose, you
can adjust the system volume using the Four.1i's volume knob. This allows you to
leave the source volume at it's maximum un-clipped level, resulting in the best
signal to noise ratio and dynamic range output from the source.
Fader: Because there is
only one stereo line input and both front and rear line outputs, the front panel
fader knob is needed to adjust the relative front and rear volume.
Input Gain: The input gain for the left and right channels
is set independently; 0 dB to +20 dB. The +20 dB gain allows you to increase the
head unit's line voltage to the top of your amp's input range; up to 9.5 volts RMS/13 volts peak.
Inputs/Outputs: Using the balanced differential input circuit cancels
noise picked up in the transmission line between the Four.1i the the source
unit, or between the Four.1i and the amplifiers. Both the main and auxiliary
inputs and the outputs can be individually set to balanced or unbalanced, incase
your amps don't accept balanced inputs.
Ground Isolation: The power supply ground is switchable, in case of
ground loop noise. The factory position is fully isolated (typically the best
choice), but can be changed to Ground or 200Ω.
Terminal Block: The
power/ground/remote/illumination terminal is removable; the wiring is attached
to the block, then the block is plugged into the rear panel of the Four.1i.
Illumination: The outer ring of each knob is lit whenever the
illumination terminal is energized. The color is switchable between green and
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