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34829_HK_CA280_OM.qxd:34829_HK_CA280_OM  16/10/07  11:13  Side 9

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Harman Kardon CA280 Car Amplifier

Service Manual

CONTENTS:
CONNECTIONS AND SPECIFICATIONS...2
EXPLODED VIEW.......................................4
ELECTRICAL PARTS LIST.........................5
BLOCK DIAGRAM.......................................9
SCHEMATIC DIAGRAMS...........................10

0

1

2

A

B

C

D

9-1/4"

234mm

2-1/2"

62mm

3

7 8

B

4

6

D

C

5

E

9 A

11-3/16"

284mm

A

B

C

D

E

F

G

2x

4x

1x – 3mm

1x

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Installation Warnings and Tips:
• Disconnect the negative (–) lead from your vehicle’s

battery.

• At the installation sites, locate and make a note of all

fuel lines, hydraulic brake lines, vacuum lines and elec-
trical wiring. Use extreme caution when cutting or
drilling in and around these areas.

• Choose a safe mounting location away from moisture. 
• Make sure there is sufficient air circulation at the

mounting location for the amplifier to cool itself.

• Mount the amplifier, using the supplied hardware.

Specifications
• 110W RMS x 2 channels @ 4 ohms and ≤1% THD + N*
• 160W RMS x 2 channels @ 2 ohms and ≤1% THD + N*
• THD+N: 0.05% (rated power @ 4 ohms)
• Signal-to-noise ratio: 85dBA 

(reference 1W into 4 ohms)*

• Signal-to-noise ratio: 106dBA 

(reference rated power into 4 ohms)

• Frequency response: 14Hz – 100kHz (–3dB)
* CEA-2006A-compliant

0 Speaker Output Connectors

• Connect the speakers to these terminals, observing

proper polarity:

• Two-channel operation: Connect the left speaker

to the L+ and L– terminals and the right speaker
to the R+ and R– terminals. 

• One-channel (bridged) operation: Connect the

single speaker to the L+ and R– terminals.

• Minimum speaker impedance for stereo operation

is 2 ohms. Minimum speaker impedance for
bridged operation is 4 ohms.  

1 Fuses

• Replace only with the same type and rating.

2 Power Input Connectors 

• +12V: Connect to the positive terminal of the vehi-

cle’s battery. 8 AWG (

5,2 mm) wire is recommended.

Install an appropriate fuse holder and fuse (40A
minimum) within 18 inches of the battery. Make
sure the wire is not damaged or pinched during
installation. Install protective grommets when rout-
ing wires through the firewall or other sheet metal. 

• GND: Connect to the vehicle’s chassis. Refer to 

the illustration below. 

• REM: Connect to the “Remote Out” lead from the

source unit or to a source of switched 12V+ (ACC).

3 Subsonic Filter Frequency Control

• Provides a 12dB/octave high-pass filter. The 

frequency can be varied between 10Hz and 
80Hz. Useful when channels 3 and 4 will be 
used to drive a subwoofer or separate mid-bass
speakers. See “Setting the Crossover” for use 
with mid-bass speakers.

• When subwoofers in vented enclosures are used,

set this control 10Hz below the frequency at which
the enclosure is tuned.

4 Crossover-Frequency Control

• 12dB/octave crossover, variable from 32Hz to

320Hz. See 

G for the adjustment procedure.

5 Crossover-Filter Selector

• LP: Select for subwoofer(s) or to provide a low-pass

filter for separate mid-bass speakers. The subsonic
filter will provide a high-pass filter for separate
mid-bass speakers.

• FLAT: Select for full-range speakers when 

no subwoofer will be used in the system.

• HP: Select for midrange speakers or full-range

speakers when a subwoofer is used in the system.

6 Gain (Input Level) Control

• Used to match the input level of the amplifier to 

the output level of the source unit. See 

F for the

adjustment procedure.

7 Input Management System (IMS) Input Connector

(RJ45 Ethernet Cable)
• When used with the IMS, this connector provides 

a single connection for front, rear, subwoofer and
remote turn-on.

8 Input Management System (IMS) Output

Connector (RJ45 Ethernet Cable)
• When the IMS input connector is connected to 

the IMS, this output will pass the IMS signal (see
above) to an additional amplifier that includes an
IMS input connector.

9 Input Connectors (RCA)

• Connect to front RCA outputs from the source unit

or signal processor.

A Aux Output Connectors (RCA)

• Nonfiltered pass-through output. Connect to the

input of an additional amplifier.

B Protect LED

• Illuminated under any of the following fault 

conditions: battery over/under voltage, short 
circuit in speaker wires, amplifier is too hot, ampli-
fier’s output circuit has failed (DC voltage present in
the amplifier’s output). 

C Channel Assignment Switch

• Determines the routing of the input signal for the

RCA and IMS inputs. 

• LEFT: Sends the input signal from the left input 

to both amplifier channels, useful if you are 
bridging the amplifier.

• STEREO: Sends the signals from the left input 

to the left output channel and the signal from 
the right input to the right output channel. 
(This is typical operation mode.)

• RIGHT: Sends the input signal from the right input to

both output channels, useful if you are bridging the
amplifier.

D Input Assignment Switch (IMS)
Note: Only functional when using the IMS input.

• FRT: Sends the IMS front stereo signal to the 

amplifier’s inputs.

• REAR: Sends the IMS rear stereo signal to 

the amplifier’s inputs.

• SUB: Sends the IMS mono signal to the 

amplifier’s inputs.

E Power On LED

• Illuminated when the amplifier is on.

F Setting Gain (Input Level)

A Turn Gain control counterclockwise to 

MIN (minimim).

B With a dynamic music track playing, turn the 

head unit’s volume control to the 3/4 position.

C Turn Gain control clockwise until the music 

is so loud that it no longer sounds clear 
(distortion is present in the output).

D Turn Gain control counterclockwise gradually, 

just until the music sounds clear, once again.

E Input Gain is now adjusted correctly.

G Setting the Crossover

A Crossover setting for 5" or larger full-range

speakers when no subwoofer is included in 
the system.

B Crossover setting for full-range speakers 

when a subwoofer is included in the system.

C Crossover setting for subwoofers.
D Crossover setting for separate mid-bass 

speakers driven by channels that include 
a Subsonic Filter Control.

Note: Acceptable frequency ranges indicated 

in gray.

0

1

2

A

B

C

D

9-1/4"

234mm

2-1/2"

62mm

3

7 8

B

4

6

D

C

5

E

9 A

11-3/16"

284mm

A

B

C

D

E

F

G

2x

4x

1x – 3mm

1x

This product is designed for mobile applications and is not 
intended for connection to the mains. 
A valid serial number is required for warranty coverage. 
Features, specifications and appearance are subject to change
without notice. 

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