Kenwood KAC 8404 Manual

The Kenwood KAC 8404 is a high-performance 4-channel car amplifier designed to deliver exceptional audio quality with 50W RMS per channel at 4 ohms. Features include MOSFET power supply, variable high-pass/low-pass filters, bass boost, speaker-level inputs, and comprehensive protection circuits. Below are key sections for safety, features, installation, setup, operation, and troubleshooting.

1. Features at a Glance 2. Installation 3. First-Time Setup 4. Specifications 5. Controls and Settings 6. Connecting Devices 7. Operation Modes 8. Protection Features 9. Care & Maintenance 10. Regulatory Information 11. Troubleshooting

Features at a Glance

Key components: MOSFET power supply, variable crossover network, bass boost control, speaker-level inputs, thermal protection.

Feature	Description
Power Output	50W RMS x 4 channels at 4 ohms
MOSFET Power Supply	Efficient and reliable power delivery
Variable Crossover	High-pass and low-pass filter adjustments
Bass Boost	+12dB boost at 50Hz
Speaker-Level Inputs	Direct connection to factory head units
Protection Circuit	Thermal, short-circuit, and DC offset protection
Bridgeable	Can be bridged for 2-channel operation
Low-Pass Filter	50Hz-200Hz frequency range
High-Pass Filter	50Hz-200Hz frequency range
Input Sensitivity	200mV-4V adjustable

Installation

Unpack and inspect contents. Choose suitable mounting location.

Disconnect negative battery terminal before installation.
Mount amplifier: Secure to solid surface with proper ventilation.
Connect power: Run 8-gauge power cable from battery to amplifier.
Connect ground: Use short, thick cable to clean metal chassis point.
Connect remote turn-on: Connect to head unit's remote output.
Connect speakers: Use appropriate gauge speaker wire.
Connect audio inputs: Use RCA cables or speaker-level inputs.

WARNING! Ensure proper fuse rating and secure all connections to prevent short circuits.

First-Time Setup

Reconnect battery and power on system; adjust settings gradually.

Set input sensitivity: Start at minimum, increase until distortion occurs, then back off.
Adjust crossover: Set high-pass for front/rear speakers, low-pass for subwoofers.
Set bass boost: Use sparingly to avoid distortion.
Balance channels: Ensure equal output from all channels.
Test operation: Play audio at various volume levels to check performance.

CAUTION! Avoid setting gains too high to prevent speaker damage and distortion.

Specifications

RMS Power: 50W x 4 at 4 ohms (20Hz-20kHz, 0.08% THD)
Max Power: 100W x 4 at 4 ohms
Bridged Power: 150W x 2 at 4 ohms
Frequency Response: 10Hz-50kHz (+0, -1dB)
Signal-to-Noise Ratio: >100dB
Input Sensitivity: 200mV-4V (RCA), 0.5V-10V (speaker level)
Crossover Frequency: 50Hz-200Hz (high-pass/low-pass)
Bass Boost: +12dB at 50Hz
Dimensions: 9-13/16" W x 2-3/8" H x 7-7/8" D
Fuse Rating: 25A x 2

Controls and Settings

Access controls via top panel knobs and switches.

Front Panel: POWER indicator (green=normal, red=protection), INPUT SENSITIVITY knobs, BASS BOOST control, CROSSOVER frequency controls, CROSSOVER mode switches (HPF/FLAT/LPF).

Input Sensitivity: Adjust to match head unit output level. Bass Boost: Increases low-frequency output. Crossover: HPF for speakers, LPF for subwoofers. Mode Switches: Select filter type for each channel pair.

Connecting Devices

Power: Battery connection with fuse. Audio: RCA inputs or speaker-level inputs. Speakers: 4-channel or bridged 2-channel output.

Turn off vehicle and disconnect battery before connections.
Match input type to source (RCA for aftermarket, speaker-level for factory).
Use proper gauge wire for power and speakers.
Ensure secure ground connection to bare metal.

Tip: Keep power and audio cables separated to reduce noise interference.

Operation Modes

Supports 4-channel stereo and bridged mono operation.

4-Channel Mode: Standard operation for front and rear speakers.
Bridged Mode: Combine channels 1+2 and 3+4 for higher power.
Tri-Mode: Use channels 1+2 for front speakers, bridge 3+4 for subwoofer.
Crossover Settings: Adjust based on speaker capabilities and installation.
Input Selection: Choose between RCA and speaker-level inputs.

WARNING! Do not ground speaker outputs or connect below minimum impedance.

Protection Features

Thermal Protection: Automatically reduces output when overheated. Short-Circuit Protection: Shuts down if speaker wires short. DC Offset Protection: Prevents DC voltage to speakers. Over-Current Protection: Limits current during faults.

Care & Maintenance

Keep amplifier clean and dry. Ensure proper ventilation. Check connections periodically for corrosion or looseness.

CAUTION! Do not block ventilation openings. Avoid exposure to moisture and extreme temperatures.

Regulatory Information

FCC Part 15: Class B digital device; complies with interference limits. Copyright © Kenwood Corporation. All trademarks property of their respective owners. For support, visit www.kenwood.com or contact authorized Kenwood service centers.

Troubleshooting

Symptom	Possible Cause	Corrective Action
No power	Fuse/wiring	Check main fuse and power connections; verify remote turn-on wire.
Protection mode	Short circuit/overheat	Check speaker wires for shorts; allow amplifier to cool; verify impedance.
Distorted sound	Gain settings/input	Reduce input sensitivity; check source unit output; verify proper grounding.
No sound from channels	Wiring/settings	Check speaker connections; verify crossover settings; test with known good source.
Engine noise	Grounding/cable routing	Improve ground connection; reroute RCA cables away from power wires.

Reset: Disconnect power for 30 seconds to reset protection circuits.

Service: Contact authorized Kenwood service center; www.kenwood.com