Kenwood KAC 646X Manual

The Kenwood KAC 646X is a 4-channel car amplifier designed for high-performance audio systems, featuring MOSFET power supply, variable high-pass/low-pass filters, speaker-level inputs, bridgeable channels, and thermal/overload/short circuit protection. With 60W RMS per channel at 4 ohms and capable of 2-ohm stable operation, this amplifier delivers clean power for your car audio setup. 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 controls, speaker-level inputs, bridgeable channels, thermal protection circuitry.

Feature	Description
MOSFET power supply	For efficient power delivery and reduced heat
Variable high-pass filter	Adjustable from 50Hz to 250Hz
Variable low-pass filter	Adjustable from 50Hz to 250Hz
Speaker-level inputs	For connection to factory head units
Bridgeable channels	Channels 1/2 and 3/4 can be bridged for more power
RCA inputs	For standard line-level connections
Power and protection LEDs	Indicates power status and protection mode activation
Gain controls	Adjustable input sensitivity for each channel
Bass boost	+12dB boost at 50Hz
Remote turn-on capability	For automatic power on/off with head unit

Installation

Unpack and inspect contents. Choose proper mounting location.

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

WARNING! Ensure proper fuse rating and secure all connections. Do not run power wires near audio cables.

First-Time Setup

After installation, configure amplifier settings.

Set gain controls: Start at minimum, adjust while playing test tone.
Configure crossover: Set HPF for front/rear speakers, LPF for subwoofers.
Set bass boost: Use sparingly to avoid distortion.
Test all channels: Verify proper operation of each speaker.
Balance fade/balance: Use head unit controls for optimal soundstage.

CAUTION! Set gains properly to avoid clipping and speaker damage.

Specifications

RMS Power: 60W x 4 channels at 4 ohms
Bridged Power: 150W x 2 channels at 4 ohms
Frequency Response: 10Hz - 50,000Hz
Signal-to-Noise Ratio: >100dB
THD: <0.08%
Crossover Frequency: 50-250Hz variable
Bass Boost: +12dB at 50Hz
Input Sensitivity: 200mV - 4V
Fuse Rating: 25A x 2
Operating Voltage: 14.4V DC (11-16V range)

Controls and Settings

Front panel controls: Power LED, Protection LED, Input level controls, Crossover controls.

Rear Panel: Power/ground terminals, Remote turn-on, RCA inputs, Speaker outputs, Fuse holders.

Input Level: Adjust gain for each channel pair. Crossover: HPF/LPF selection and frequency adjustment. Bass Boost: +12dB boost at 50Hz. Input Mode: Select RCA or speaker-level input.

Connecting Devices

RCA Inputs: Standard line-level connections. Speaker-level Inputs: For factory head units.

Turn off vehicle and disconnect battery before connections.
Match RCA cables to appropriate channels (front/rear/sub).
Use proper gauge wire for power/ground connections.
Ensure secure speaker connections with proper polarity.
Connect remote turn-on to head unit's blue wire.

Tip: Keep power wires separated from audio cables to reduce noise.

Operation Modes

Supports stereo, bridged, and mixed operation modes.

Stereo Mode: Standard 4-channel operation for front/rear speakers.
Bridged Mode: Channels 1/2 and 3/4 bridged for more power.
Mixed Mode: Front channels for speakers, rear channels bridged for subwoofer.
Crossover Settings: HPF for full-range speakers, LPF for subwoofers.
Input Selection: Switch between RCA and speaker-level inputs.

WARNING! Do not bridge channels to impedance lower than 4 ohms.

Protection Features

Thermal Protection: Automatically shuts down if temperature exceeds safe limits. Overload Protection: Protects against excessive current draw. Short Circuit Protection: Safeguards against speaker wire shorts. DC Offset Protection: Prevents DC voltage to speakers.

Care & Maintenance

Keep amplifier clean and free of debris. Ensure proper ventilation. Check connections periodically for corrosion or looseness.

CAUTION! Do not cover amplifier or block ventilation. Keep away from moisture.

Regulatory Information

FCC Part 15: Class B digital device; complies with interference limits. CE certified for European markets. Copyright © Kenwood Corporation. For support, visit www.kenwood.com or contact authorized service centers.

Troubleshooting

Symptom	Possible Cause	Corrective Action
No power	Power/ground connections	Check battery connection; verify ground; check fuses.
Protection mode active	Short circuit/overheating	Check speaker wires for shorts; allow amplifier to cool.
Distorted sound	Gain settings/clipping	Reduce gain settings; check head unit output levels.
No sound from channels	Input connections/settings	Verify RCA connections; check input mode selection.
Engine noise	Ground loop/poor grounding	Improve ground connection; reroute audio cables.

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

Service: Contact authorized Kenwood service centers for repairs.