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© B64-3922-00/00 (KV/EV)
7 page 2-9
7 page 10-17
7 página 18-25
Take the time to read through this instruction manual.
Familiarity with installation and operation procedures will help you obtain the best
performance from your new power amplifier.
For your records
Record the serial number, found on the back of the unit, in the spaces designated on the
warranty card, and in the space provided below. Refer to the model and serial numbers
whenever you call upon your Kenwood dealer for information or service on the product.
Model KAC-7404, KAC-6404 Serial number
US Residence Only
Register Online
Register your Kenwood product at
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2 English
Safety precautions
To prevent injury or fire, take the following
· When extending the ignition, battery, or ground
wires, make sure to use automotive-grade wires
or other wires with a 5 mm² (AWG 10) or more to
prevent wire deterioration and damage to the wire
· To prevent a short circuit, never put or leave any
metallic objects (such as coins or metal tools) inside
the unit.
· If the unit starts to emit smoke or strange smells,
turn off the power immediately and consult your
Kenwood dealer.
· Do not touch the unit during use because the
surface of the unit becomes hot and may cause
burns if touched.
· Mounting and wiring this product requires skills and
experience. For safety's sake, leave the mounting and
wiring work to professionals.
To prevent damage to the machine, take
the following precautions:
· Be sure the unit is connected to a 12V DC power
supply with a negative ground connection.
· Do not open the bottom covers of the unit.
· Do not install the unit in a spot exposed to direct
sunlight or excessive heat or humidity. Also avoid
places with too much dust or the possibility of water
· When replacing a fuse, only use a new one with the
prescribed rating. Using a fuse with the wrong rating
may cause your unit to malfunction.
· To prevent a short circuit when replacing a fuse, first
disconnect the wiring harness.
· If you experience problems during installation,
consult your Kenwood dealer.
· If the unit does not seem to be working right,
consult your Kenwood dealer.
To prevent battery from running out
When the unit is used in the ACC ON position without
turning the engine ON, it depletes the battery. Use it
after starting the engine.
Cleaning the unit
If the front panel gets dirty, turn off the power and
wipe the panel with a dry silicon cloth or soft cloth.
Do not wipe the panel with a hard cloth or a cloth
dampened by volatile solvents such as paint thinner
and alcohol. They can scratch the surface of the panel
and/or cause the indicator letters to peel off.
Protection function
The protection function is activated in the following
This unit is equipped with a protection function for
protecting this unit and your speakers from various
accidents or problems that can occur.
When the protection function is triggered, the Power
indicator goes off and the amplifier stops operating.
· When a speaker wire may be short-circuited.
· When a speaker output contacts ground.
· When the unit malfunctions and a DC signal is sent
to the speaker output.
· When the internal temperature is high and unit
won't operate.
· When a ground wire of the center unit (cassette
receiver, CD receiver, etc.) or this unit is not
connected to a metal part serving as an electrical
ground passing electricity to the battery's negative
- terminal.

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· Do not install in the below locations;
(Unstable location, In a location that interferes
with driving, In a location that gets wet, In a dusty
location, In a place that gets hot, In a place that gets
direct sunlight, In a location that gets hit by hot air)
· Do not install the unit under the carpet. Otherwise
heat build-up occurs and the unit may be damaged.
· Install this unit in a location which allows heat to
easily dissipate.
Once installed, do not place any object on top of the
· The surface temperature of the amplifier will become
hot during use. Install the amplifier in a place
where people, resins, and other substances that are
sensitive to heat will not come into contact with it.
· This unit has cooling fan to decrease the internal
temperature. Do not mount the unit in a place where
the cooling fan and ducts of the unit are blocked.
Blocking these openings will inhibit the cooling of
the internal temperature and result in malfunction.
· When making a hole under a seat, inside the trunk,
or somewhere else in the vehicle, check that there
is nothing hazardous on the opposite side such as a
gasoline tank, brake pipe, or wiring harness, and be
careful not to cause scratches or other damage.
· Do not install near the dashboard, rear tray, or air bag
safety parts.
· The installation to the vehicle should securely fasten
the unit to a place in which it will not obstruct
driving. If the unit comes off due to a shock and hits
a person or safety part, it may cause injury or an
· After installing the unit, check to make sure that
electrical equipment such as the brake lamps,
turn signal lamps and windshield wipers operate
Installation board, etc.
(thickness : 15 mm or more)
Self-tapping screw
(ø4 × 16 mm)
330 mm
236 mm
Part name
Number of
Self-tapping screws
(ø4 × 16 mm)
Terminal cover
(Power terminal)
Speaker level input
Cooling fan
Cooling fan

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4 English
1 A ch FILTER switch
This switch allow filtering of the speaker output
· OFF position:
The original sound without filtering is output.
· HPF (High Pass Filter) position:
Only frequencies of 80 Hz or higher are output.
(Frequencies below 80 Hz are cut.)
2 B ch FILTER switch
This switch allow filtering of the speaker output
· OFF position:
The original sound without filtering is output.
· LPF (Low-Pass Filter) position:
The filter outputs the band of lower frequencies
than the frequency set with the "LPF
FREQUENCY" control.
The speaker output is automatically turned
monaural (L+R) and the gain is enhanced.
Set this control according to the pre-output level of
the center unit connected with this unit, or to the
maximum power output of the genuine-accessory
car stereo.
Use the diagram on the right as a guide.
The sensitivities of amplifiers A and B can be
adjusted independently.
4 B ch LPF FREQUENCY control
Sets the cutoff frequency when the "B ch FILTER"
switch is set to "LPF".
5 Power indicator
When the power is turned on, the Power indicator
If the Power indicator does not light when the
power is turned on, the protection function may be
activated. Check whether there is any indication of
trouble. Refer to <Protection function> (page 2).

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Installation procedure
Since there are large variety of settings and
connections possible according to applications, read
the instruction manual well to select the proper
setting and connection.
1. Remove the ignition key and disconnect the
- terminal of the battery to prevent short
2. Set the unit according to the intended usage.
3. Connect the input and output wires of the units.
4. Connect the speaker wires.
5. Connect the power wire, power control wire and
grounding wire following this order.
6. Install the installation fittings in the unit.
7. Attach the unit.
8. Connect the negative
- terminal of the battery.
To prevent fire caused by a short in the wiring,
connect a fusible link or breaker nearby the battery's
positive terminal.
· If sound is not output normally, immediately turn
power off and check connections.
· Be sure to turn the power off before changing the
setting of any switch.
· If the fuse blows, check wires for shorts, then replace
the fuse with one of the same rating.
· Check that no unconnected wires or connectors are
touching the car body. Do not remove caps from
unconnected wires or connectors to prevent short
· Connect the speaker wires to appropriate speaker
connectors separately. Sharing the negative wire of
the speaker or grounding speaker wires to the metal
body of the car can cause this unit to fail.
· After installation, check that the brake lamps,
winkers, and wipers work properly.
· Take the battery wire for this unit directly from the
battery. If it's connected to the vehicle's wiring
harness, it can cause blown fuses etc.
· If a buzzing noise is heard from the speakers when
the engine is running, connect a line noise filter
(optional) to each of the battery wire.
· Do not allow the wire to directly contact the edge of
the iron plate by using Grommets.
· Connect the ground wire to a metal part of the car
chassis that acts as an electrical ground passing
electricity to the battery`s negative
- terminal.
Do not turn the power on if the ground wire is not
· Be sure to install a protective fuse in the power
cord near the battery. The protective fuse should
be the same capacity as the unit's fuse capacity or
somewhat larger.
· For the power cord and ground, use a vehicle type
(fireproof ) power wring cord with a current capacity
greater than the unit's fuse capacity. (Use a power
wiring cord with a diameter of 5 mm² (AWG 10) or
· When more than one power amplifier are going
to be used, use a power supply wiring wire and
protective fuse of greater current-handling capacity
than the total maximum current drawn by each
Speaker selection
· The input power of the speakers that are going to
be connected should be greater than the output
power (in Watts) of the amplifier. Use of speakers
having input power ratings that are less than the
output power of the amplifier will cause smoke to
be emitted as well as damage.
· The impedance of the speakers that are going
to be connected should be 2 or greater (for
stereo connections), or 4 or greater (for bridged
connections). When more than one set of speakers
are going to be used, calculate the combined
impedance of the speakers and then connect
suitable speakers to the amplifier.
Combined impedance