Infinity 5760-A Service manual

Reference Series

5760a

6 CHANNEL POWER AMPLIFIER

SERVICE MANUAL

Infinity Systems, Inc.

250 Crossways Park Dr.

Woodbury, New York 11797 Rev1 8/2004

Power Amplifier Ref5760a

- CONTENTS -

SPECIFICATIONS ………………………………….……..1

FEATURES/TEST CONDITIONS……..…………………2

CONTROLS/CONNECTIONS………….……..…...…..…3

INSTALLATION………………….……...……..…...…...…5

BASIC TROUBLESHOOTING..…….…….………………8

TYPICAL SYSTEM WIRING..…….…….……………..…9

EXPLODED VIEW/PARTS LIST…………………..…....10

MECHANICAL PARTS LIST…………………………….11

AMPLIFIER BLOCK DIAGRAM…………………………12

P.C.B. DRAWINGS….…………………………………….13

ELECTRICAL PARTS LIST ……………………………. 17

IC/TRANSISTOR PINOUTS..……………………….. …..21

SCHEMATICS………..…………….……………………...24

PACKING…………………………….…………………….28

Reference 5760a Specifications

Output Power: 56W RMS x 4 and107W RMS x 2 channels @ 4 ohms; ≤1% THD + N

80W RMS x 4 and150W RMS x 2 channels @ 2 ohms; ≤1% THD + N

148W RMS x 2 and 287W RMS x 1 channels @ 4 ohms; ≤1% THD + N

Signal-to-noise ratio: 82dBA (reference 1W into 4 ohms)

Dynamic power: 117W channels 1,2,3,4; 163W channels 5,6 @ 2 ohms

Effective damping factor: 6.373 @ 4 ohms

Frequency response: 10Hz – 57kHz channels 1,2,3,4; 10Hz – 302Hz channels 5,6

Maximum input signal: 6.3V

Maximum sensitivity: 250mV

DC Offset <50mV (-50%)

Output regulation: .063dB @ 4 ohms

Idle Current 2.1A

Input Impedance 22kΩ

Max Current Draw 34A @ 4 ohms

88A @ 2 ohms

89.5 @ 4 ohm bridged

Dimensions: 12 x 18 1/2 x 2 11/16” (L x W x D)

(305mm x 470mm x 68mm)

Fuse: 2 x 30A

Infinity continually strives to update and improve existing products, as well as create new ones. The specifications and details in this and related JBL publications are therefore subject to change without notice.

Power Amplifier Ref5760a

Features

• 4-Channel Operation

• Advanced MOSFET Oversized Floating Rail Power Supply

• Floating Ground Factory

• Variable lnput Sensitivity (250mV

• Fully Complementary Output Stage with Class-A6 Voltage Amplification

• Gold-plated Power, lnput and Output Connectors

• 2-Ohm Stable (Stereo)

- Head - Unit Speaker - Level input

- 6V)

Test Conditions and Notes

• All tests to be done, unless otherwise specified, from 10Hz to 47KHz and 302Hz at 14.4V DC into 4 ohm loads and adjust the units gain so that with a .775 volt input signal the unit is at Its maximum rated output. All measurements will be done using an Audio precision system one and the supply voltage.

• An A+ line voltage of 14.4V DC shall be applied to the unit under test for all measurements unless otherwise specified. The voltage applied to the unit shall be measured at the power connection on the Amplifier.

• Signal Source Unless otherwise specified, all tests shall be conducted with the Audio Signal Generator output configured to be balanced, less than or equal to 50 ohm source impedance, and floating. The signal source "GND" shall be connected to the Amplifier PWR GND at the Amplifier.

• Output Load Unless otherwise specified, all tests shall be conducted with 4 ohm resistive loads having less than 10% reactive components at any frequency below 47KHz and 302Hz. Each resistor shall have a value that remains within 1 dissipating the rated output of the unit under test.

• Power Indicator Green LED steadily illuminates for normal operation. Illuminates

up Red LED blinks when protection circuitry is engaged, and during power up.

% while

The Reference amplifiers are capable of delivering high power levels, and require a reliable connection to the vehicle’s electrical system in order to perform optimally. See Figure 1 for connection location. Please adhere to the following instructions carefully.

GROUND CONNECTION

Connect the amplifier’s Ground (GND) terminal to a solid point on the vehicle’s metal chassis, as close to the amplifier as possible. Refer to the chart below to determine minimum wire-gauge size. Sand away any paint from this location; use a star-type-lock washer to secure the connection.

POWER CONNECTION

Connect a wire (see chart at right for appropriate gauge) directly to the vehicle’s positive battery terminal, and install an appropriate fuse holder within 18" of the battery terminal. Do not install the fuse at this time. Route the wire to the amplifier’s location, and connect it to the amplifier’s positive (+12V) terminal. Be sure to use appropriate grommets whenever routing wires through the firewall or other sheet metal. Failure to adequately protect the positive wire from potential damage may result in a vehicle fire. When you are done routing and connecting this wire to the battery and to the amplifier, you may install the fuse at the battery. The fuse value should be selected based on total amplifier-current draw; see chart at right.

REMOTE CONNECTION

Connect the amplifier’s Remote (REMOTE) terminal to the source unit’s Remote Turn-On lead using a minimum of 18-gauge wire. If your source unit does not have a remote turn-on connection, connect the amplifier’s (REMOTE) terminal to the vehicle’s accessory circuit.

WIRE-GAUGE CHART

Amplifier Maximum Minimum Model Current Draw Wire Gauge

7520a 34A #8 AWG 7540a 85A #8 AWG 5760a 87A #8 AWG 310a 40A #8 AWG 610a 69A #6 AWG 1210a 115A #4 AWG

These recommendations assume 7' – 10' wire runs. If your installation differs markedly, you will need to adjust the wire gauge accordingly.

SPEAKER CONNECTIONS

Refer to the application guides on the pages that follow. Speaker connections should be made using a minimum of 16-gauge wire.

HIGH-LEVEL INPUT CONNECTIONS

The 7520a, 7540a and 5760a amplifiers are equipped with speaker-level inputs that allow you to add an amplifier to head units that do not have RCA line outputs. The speaker outputs for the source unit should be connected to the amplifier using the supplied connector (square four-wire plug). Remember to check for proper polarity. The 310a, 610a and 1210a amplifiers are not equipped with high-level inputs.

NOTE: When using the low-level or high-level inputs, the AUX outputs can be used to pass a full-range line-level signal to another amplifier.

Figure 2. Speaker-level connector.

POWER CONNECTIONS

Figure 1.Terminal-connection end plate.

HIGH LEVEL

INPUT

Speaker Wires

(spliced)

– L +

– R +

+ WHITE

– WHITE/BLACK

GRAY/BLACK –

GRAY +

Power Amplifier Ref5760a

The 5760a can be configured for 6-channel, 5-channel or 3-channel operation, as shown in Figures 10 through 12.

INPUT MODE SWITCH:

• Use INT (internal mode) to send a signal from the front and rear inputs to the subwoofer.

• Use EXT (external mode) when sending a dedicated signal to the subwoofer inputs; e.g., if your source unit has a subwoofer output.

NOTE: For simplicity, Figures 10 through 12 do not show power, remote and input connections.

NOTE: Minimum speaker impedance for stereo operation is 2 ohms. Minimum speaker impedance for bridged operation is 4 ohms.

APPLICATIONS – 5760a

Figure 10. 6-Channel operation: 5760a amplifier driving full-range front and rear speakers and a pair of subwoofers.

Figure 11. 5-Channel operation: The same as Figure 10, with the subwoofer output bridged to drive a single 4-ohm subwoofer, providing

the speaker with more power.

Figure 12. 3-Channel operation: 5760a amplifier configured for 3-channel operation, where all of the channels are bridged for a subwoofer and a pair of component speakers.

Power Amplifier Ref5760a

Figure 13. Control end panel.

5760a

Power Amplifier Ref5760a

INSTALLATION AND SETUP

SETTING THE CROSSOVER(S)

Determine your system plans and set the crossover-mode switch accordingly. If your system design does not include a subwoofer, set the crossover mode to FLAT and skip to “Setting Input Sensitivity.”

MODE SWITCH Flat: Allows a full-range signal through to the

speakers; can be used with larger full-range speakers such as 6" x 9"s. HP: Allows a high-pass signal through to the speakers; should be used with most loudspeakers (can protect your full-range speakers from being overdriven with low frequencies, one cause of speaker damage). LP: Allows bass to pass through to the speakers; should be selected when powering subwoofers.

Initially set the crossover-frequency control midway. While listening to music, adjust the crossover for the least perceived distortion from the speakers, allowing them to reproduce as much bass as possible.

Systems using a separate subwoofer set the crossover mode to HP (high pass) for your full-range speakers. Adjust the crossover frequency to limit bass, and provide increased system volume with less distortion.

For subwoofers, choose the highest frequency that removes vocal information from the sound of the subwoofer.

If using the 7520a or 7540a to drive a subwoofer(s), set the crossover mode to LP (low pass).

NOTE:The 310a, 610a, 1210a and the subwoofer output of the 5760a are low-pass only and do not have a crossover-mode switch.

Figure 13. Control end panel.

SETTING INPUT SENSITIVITY

1. Initially turn the INPUT LEVEL control(s) to minimum (counterclockwise).

2. Reconnect the (–) negative lead to the vehi-

cle’s battery. Apply power to the audio system and play a dynamic music track.

3. On the source unit, increase the volume

control to 3/4 volume. Slowly increase the INPUT LEVEL control(s) toward three o’clock until you hear slight distortion in the music. Then reduce the INPUT LEVEL slightly until distortion is no longer heard.

NOTE: After the source unit is on, blue LEDs (on the top panel) will light, indicating the amplifier is on. If not, check the wiring, especially the remote connection from the source unit. Also refer to “Troubleshooting” on the page 7.

5760a

REMOTE LEVEL CONTROL (OPTIONAL)

All three Reference subwoofer amplifiers and the 5760a amplifier have inputs for an optional remote level control (100rc). This will allow the subwoofer level to be adjusted from the listening position. Connect the optional remote level control using the RJ-11 jack on the side of the amplifier. Install the control module in the front of the vehicle within easy reach of the driver. Both the underside of the dash and the center console are suitable locations. Refer to the mounting instructions accompanying the 100rc.

SETTING THE BASS BOOST

The 7520a, 7540a and 5760a are all equipped with a bass-boost control. This allows you to enhance the bass output of your system at 50Hz up to 12dB.

NOTE: Only rear channels of the 7540a are affected by the bass boost control.

AUX OUTPUT

Reference amplifiers (except 5760a) are equipped with full-range outputs that can be used to connect additional amplifiers.

NOTE: When using the low- or high-level inputs, the AUX outputs can be used to pass a full-range line-level signal to another amplifier.

Power Amplifier Ref5760a

STATUS LEDs Clip: Indicates the amplifier is being overdriven,

and your speakers may be in danger. This should blink only on musical peaks, and not be on constantly.

Power: Indicates the amplifier is on. Protection: Refer to “Troubleshooting” for specific

indications.

Figure 15.

LED status.

SETTING DBO™(310a, 610a and 1210a)

The Dynamic Bass Optimizer (DBO) is used to enhance low-frequency reproduction in a vehicle. Conventional bass-boost circuits only increase bass at a fixed frequency, and cause the amplifier to consume considerable power. The DBO allows you to adjust the frequency (20Hz – 80Hz) as well as the boost level (up to 12dB; see Figure 14), allowing you to fine-tune the bass in your system to optimize performance.

For sealed enclosures, the DBO can be used to enhance the lower bass region of sealed enclosures.

For bigger/fuller bass, adjust the HP FREQ between 35Hz and 45Hz; adjust the BOOST control according to your preference.

For tighter-sounding bass, adjust the HP FREQ between 45Hz and 55Hz; adjust the BOOST control according to your preference.

For vented enclosures, the DBO should be used as a subsonic filter to reduce overexcursion of the woofers. Set the HP FREQ control 10Hz below the tuning frequency of the enclosure (e.g., 25Hz for a box tuning of 35Hz); adjust the BOOST control to taste. This will conserve amplifier power typically wasted on frequencies below the tuned frequency of the enclosure.

For infinite-baffle applications, set the HP FREQ to the speaker’s Fs value (reducing overexcursion of the woofer); adjust the Boost control to taste.

Figure 14.

Frequency-response curves show

typical DBO control ranges.

INSTALLATION AND SETUP (CONT.)

-9

-6

-3

-12 20 80

Freq. (Hz)

DBO HP FREQ Control

(adjusts cut-off

frequency)

HP FREQ

100Hz20Hz

-6

-12 20 80

Freq. (Hz)

DBO BOOST Control

(adjusts boost amount

at cut-off frequency)

BOOST

MAX MIN

Power Amplifier Ref5760a

TROUBLESHOOTING

•

PROBLEM:

No audio (POWER LED is off).

PROBLEM:

No audio (PROTECT LED is on).

CAUSE and SOLUTION: No voltage at BATT+ and/or REM terminals, or bad or no ground connection. Check voltages at amplifier terminals with VOM.

•

PROBLEM:

No audio (PROTECT LED flashes every 4 seconds).

CAUSE and SOLUTION: DC voltage on amplifier output. Amplifier may need service; see enclosed warranty card for service information.

•

PROBLEM:

No audio (PROTECT LED is on).

CAUSE and SOLUTION: Amplifier is overheated. Make sure amplifier cooling is not blocked at mounting location; verify that speaker-system impedance is within specified limits.

•

PROBLEM:

No audio (PROTECT and POWER LEDs flash).

CAUSE and SOLUTION: Voltage less than 9V on BATT+ connection. Check vehicle charging system.

CAUSE and SOLUTION: Voltage greater than 16V or less than 8.5V on BATT+ connection. Check vehicle charging system.

•

PROBLEM:

Distorted audio.

CAUSE and SOLUTION: Input sensitivity is not set properly, or amplifier or source unit is defective. Check INPUT LEVEL setting, or check speaker wires for shorts or grounds.

•

PROBLEM:

Distorted audio (PROTECT LED flashes).

CAUSE and SOLUTION: Short circuit in speaker or wire. Remove speaker leads one at a time to locate shorted speaker or wire, then repair.

•

PROBLEM:

Music lacks “punch.”

CAUSE and SOLUTION: Speakers are not connected properly. Check speaker connections for proper polarity.

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