JBL L8400P Service Manual

Studio L Series

L8400P

Amplifier/Subwoofer

SERVICE MANUAL

JBL Consumer Products
250 Crossways Park Dr.

Woodbury, New York 11797 Rev1 3/2006

L8400P L series

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- CONTENTS -

BASIC SPECIFICATIONS…………………………………………..1
PACKAGING…………………………….……………….………….2
DETAILED SPECIFICATIONS…………………………………….3
CONNECTIONS..………………………………………………….. 5
OPERATION ………….…………………………..….….………….7
BASIC TROUBLESHOOTING…………………………………….8
EXPLODED VIEW……………………………………………….…9
120V BLOCK DIAGRAM..……………………………………..….10
PCB DRAWINGS………………..………………………………...11
120V ELECTRICAL PARTS LIST …………….…….…………..15

INTEGRATED CIRCUIT/TRANSISTOR PINOUTS………....19

120V SCHEMATICS.……….………………………..…. ………20

L8400P BASIC SPECIFICATIONS

Amplifier Power ( RMS) 600 Watts
Peak Dynamic Power * 1200 Watts
Frequency Response (–3dB) 22Hz – Low-pass crossover frequency
Low-Pass Crossover Frequencies 50Hz – 150Hz, Continuously adjustable
Low-Frequency Transducer 12" (300mm) PolyPla s ™ cone
Baffle Low diffraction, IsoPower™
Enclosure Sealed
Inputs Gold-plated 5-way binding-post speaker-level;

Left and right line-level, switchable to LFE

Outputs 150Hz when using speaker-level connection

Gold-plated 5-way binding-posts

Dimensions (H x W x D) 16-1/2" (15-1/2" without feet) x 15-1/2" x 15-1/2"

(419mm [394mm without feet] x 394mm x 394mm)

Weight 58 lb (26.4kg)

* The Peak Dynamic Power is measured by recording the highest peak-to- c enter v oltage produced by t he power

amplifi er with its limiters disabled, across the output of a resistiv e load equal to minimum impedance of the
transducer, using a 50Hz sine wavebur st, 3 cycles on, 17 cycles off.

Occasional r efinements may be made to existing product s without notice but will always meet or exceed original
specifications unless otherwise stated

L8400P

Packaging

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6

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1 3 4 7 8

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2

ITEM
NO. DESCRIPTION QTY. PART NO.

1. Owner’s Manual 1 354038-001

2. Front Grille 1 353234-001

3. Warranty Card, JBL 5YR/1YR 1 338381-001

4. Kit, Spike Foot 4 354432-001

5. L8400P Outer Carton, Black 1 353588-001
L8400P Outer Carton, Beech 1 353588-002
L8400P Outer Carton, Cherry 1 353588-003

ITEM
NO. DESCRIPTION QTY. PART NO.

6. Pad, Foam, Top, Bottom L8400P 2 353592-001

7. Y-Adapter Cable 1 354058-001

8. Foot, Bump-On 3M, SJ5744 4 330104-001

y

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L8400P L series

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L8400P Powered Sub/ Plate Amp

LINE VOLTAGE Yes/No Hi/Lo Line Nom. Unit Notes

Parameter Spec. Unit
Amp Section

Type (Class AB, D, other) D n/a
Load Impedance (speaker) 4 Ohms
Rated Output Power 450 Watts
THD @ Rated Power 0.5 %
THD @ 1 Watt 0.1 %

Dynamic Power 460 Watts
DC Offset 80 mV-DC

Damping factor >20 DF

Input Sensitivit

Input Frequency 50 Hz

Left or Right inputs 16.6 mVrms
Left & Right with LFE or LP
filter OFF Mode selected

Speaker/Hi Level Input 165 mVrms

US 120VAC/60Hz Yes 108-132 120

EU 230VAC/50-60Hz Yes 207-264 230

QA Test

Limits Conditions Notes

±2dB To 1 Watt

16.6 mVrms

±2dB To 1 Watt

±2dB To 1 Watt

Vrms Normal Operation
Vrms Normal operation, MOMS required

Bridge type amplifier, None of the speaker

n/a
n/a Nominal

380 1 input driven Measuring 425 Watts Cold

1 22K filter

0.2 22K filter

Power is the average measurement
of the first four consecutive peaks

450

of the burst signal

100 @ Speaker Outputs

15 Measured at amplifier board

30 Nominal Freq.

terminals must be connected to system
GND at any time.

3/20 Cycles @ 50 Hz, burst test into 4
Ohms, input driven 6dB above its maximum
sensitivity, volume level at Maximum.

Measured at the speaker cable. 200 Watts,
measured at speaker output terminals
located at the amp board.

Single input driven, Ap Zo=600 Ohms, LP
ON, Volume ctrl & crossover at max
Single input driven , Ap Zo=600 Ohms, LP
OFF, Volume ctrl & crossover at max
Single input driven, Ap Zo=25 Ohms,
Normal, Volume ctrl & crossover at max

Signal to Noise

SNR-A-Weighted 100 dBA

SNR-unweighted 95 dBr
SNR rel. 1W-unweighted 70 dBr

Residual Noise Floor 0.5 mVrms

Residual Noise Floor 0.5 mVrms(max)

Speaker input rejection

CMRR Speaker in >37 dB

Input Impedance

Filters

LP 4th order variable 50-150 Hz
Subsonic filter (HPF) 3rd Ord
Low pass filter OFF Fixed Hz

HP Speaker output 4 Ohms 200 Hz

HP Speaker output 8 Ohms 100 Hz

Line Input (L, R,LFE) 10K ohms

Speaker/Hi Level Input 10K ohms

Fixed Hz

90 Relative to rated power (400 Watts) A-Weighting filter

85 Relative to rated power (400 Watts) 22K filter
65 Relative to 1W Output 22K filter

Volume @max, using RMS reading

1

DMM/VOM (or A/P)
Volume @max, w/ A/P Swept
Bandpass Measurement (Line

1

freq.+ harmonics)

1.0V + RMS applied to + & - inputs

Reference

± 10
± 10
± 20 L or R input driven, LP Filter OFF

± 10 Speaker output loaded with 4 Ohms

± 10 Speaker output loaded with 8 Ohms

50 Hz, Generator GND to system
GND

n/a Nominal
n/a Nominal

Limiter

THD at Max. Output Power

Features --

Auto - On -Off YES --

YES n/a functional

functional

No switch to select the ATO mode is
provided, Refer to ATO section

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L8400P L series

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QA Test
Parameter Spec. Unit
Amp Section

Phase switch 0-180 deg
Volume pot Taper (lin/log) LOG --

Variable crossover 50-150 Hz YES

Limits Conditions Notes

functional
functional 5K A Taper

functional

4th Order LP Filter, 2nd order fix and 2nd
order variable.

HP Speaker out YES
LP On- Off Select switch YES --

On-Off indicators

Input Configuration

Line In (L,R) & LFE
Spkr/Hi Level In YES --

Signal Sensing (ATO)

Auto-Turn-On (yes/no) YES
ATO Input test frequency 50 Hz
Min ATO Level L or R Inputs 3 mV
Min ATO Level Speaker in L
or R inputs

ATO Turn-on time 2 seconds

Auto Mute/ Turn-OFF Time 5 minutes

Auto Mute/ Turn-OFF Time 15 Minutes

Power on Delay time 2 sec.

Transients/Pops

ATO Transient 5 mV-peak
Turn-on Transient 50 mV-peak
Turn-off Transient 50 mV-peak

YES

YES --

30 mV

functional Pass through from the speaker input section
functional Disables LP filter, intended for LFE

functional

functional Dual RCA jack, L or R is used in LFE mode

functional Binding post connector L&R

functional Auto - on selection switch in Auto
functional "
functional " Single input driven

functional " Single input driven

functional

1V-pk-pk @ Speaker Outputs AC Line cycled from OFF to ON
1V-pk-pk @ Speaker Outputs AC Line cycled from ON to OFF

Amp connected and AC on, then
input signal applied
(T) Time before muting, after
minimum ATO signal is removed

17

(3mV)
(T) Time before muting, after input

17

signal is removed

4 AC Power Applied

n/a @ Speaker Outputs

Unit is provided with 2 LED's BLU-ON, RED
OFF

Auto turn of time (T) must be 5 > T < 17
Minutes
Auto turn of time (T) must be 10 > T < 17
Minutes

Efficienc

Efficiency 68 %

Stand-by Input Power 18 Watts

Stand-by Input Power 22 Watts

Power Cons. @ 400W 584 Watts

Protection

Thermal Protection YES
DC Offset Protection YES
Line Fuse Rating
USA-Domestic 5 Amps

EU 2.5 Amps

65 400W of output power Nominal Line voltage 120 VAC

@ nominal line voltage, Amp in

20

OFF state, RED LED activated

@ nom. line voltage, Amp in On

25

state, Green LED activated

615 @ nom. line voltage 400 Watts into 4 Ohms nominal line voltage

functional @1/8 max unclipped Power

- DC present at Speaker Out leads Relay opens during a DC output condition

Type-T or Slo Blo-250 V
Type-T , Low Breaking capacity-250
V Internal fuse with UL/SEMKO rated holder

Maximum allowable input power LED in
RED, Class D inactive
Maximum allowable input power under
nominal Input voltage and frequency, in
stand-by mode (HOT or COLD operation,
LED GREEN). Class D active but no signal
applied.

Temperature rise in accessible metal parts
should not exceed 35K rise for domestic
version or 30K rise for European versions
(refer to requirements sheet). Unit is
protected for over-temperature conditions

L8400P L series

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DOLBY* DIGITAL OR DTS
(OR OTHER DIGITAL SURROUND MODE) CONNECTION

Use this installation method for
Dolby Digital, DTS or other dig­ital surround processors:

Use either the left or right line­level input jack for the Low­Frequency Effects channel; it
doesn’t matter which one you
choose.

DOLBY PRO LOGIC* (NON-DIGITAL) –LINE LEVEL

Use this installation method
for Dolby Pro Logic applica­tions (not Dolby Digital, DTS
or other digital processing),
where the receiver/processor
is equipped with a subwoofer
output, or a volume-controlled
preamp (line-) level output:

Use RCA-type interconnects
to connect the line-level
subwoofer outputs on your
receiver or amplifier to the
line-level inputs on the sub-

®

IMPORTANT: Make sure that
the LFE/Normal toggle switch
∞ is in the “LFE” position.
This will bypass the sub­woofer’s normal low-pass
filter, reducing the possibility
of signal degradation and more
accurately reproducing the
program materials. However, if
your receiver is passing a full­range signal through its sub­woofer output, place the tog­gle switch in the “Normal”
position, which will activate
the low-pass filter and protect

woofer. IMPORTANT: Make
sure that the LFE/Normal
toggle switch ∞ is in the
“Normal” position. This will
activate the subwoofer’s low­pass filter, protecting the sub­woofer from possible damage
and enabling it to operate most
efficiently by reproducing only
the low-frequency materials
that it is best at handling.

NOTE: If your receiver or
amplifier only has one sub-

the subwoofer from possible
damage. Connect this jack to
the LFE output or subwoofer
output on your receiver or
amplifier. Connect each
speaker to the corresponding
speaker terminals on your
receiver or amplifier.

Make sure that you have con­figured your surround sound
processor for “Subwoofer On.”
Also, remember to configure
your receiver for 5.1-, 6.1- or

7.1-channel operation as
appropriate.

woofer output jack, then you
will need to use a Y-connector
(not included). Plug the male
end of the Y-connector into
your receiver or amplifier’s
subwoofer output jack, and
connect each of the two
female ends to separate RCA­type interconnects. Finally,
plug the RCA-type intercon­nects into the line-level inputs
on the subwoofer.

Connect each speaker to
the corresponding speaker
terminals on your receiver
or amplifier.

Make sure your receiver or
processor is correctly config­ured to indicate that the sub­woofer is “On.”

Note for advanced users: If
your receiver/processor has
a built-in low-pass crossover
filter for the subwoofer output,
you may switch the LFE/
Normal toggle switch to the
“LFE” position to bypass the
subwoofer’s internal
crossover.

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L8400P L series

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DOLBY PRO LOGIC (NON-DIGITAL) –SPEAKER LEVEL

Use this installation method
for Dolby Pro Logic applica­tions (not Dolby Digital, DTS
or other digital processing),
where the receiver/processor
does not have a subwoofer
output, or a volume-controlled
preamp (line-) level output:

Connect your receiver or
amplifier’s front left and right
speaker terminals to the left
and right terminals on the
subwoofer that are marked
“Speaker Level In.” Connect
the left and right terminals
on the subwoofer that are
marked “Speaker Level Out” to
the corresponding terminals on
the back of your front left and
right speakers.

Connect your receiver or
amplifier’s center, surround
and surround back speaker
terminals to the corresponding
terminals on the back of
your center and surround
speakers.

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L8400P L series

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OPERATION

Power

Move the Master Power
¢ to the “On” position to use
the L8400P subwoofer.

Level Control

The subwoofer Level Control

• adjusts the volume of the
subwoofer relative to the rest
of the system. Proper level

Crossover Adjustments

The Crossover Frequency
Control ¶ determines the
highest frequency at
subwoofer reproduces
If your main speakers can
comfortably reproduce some
low-frequency sounds, set this
control to a lower frequency
setting, between 50Hz and
100Hz. This will concentrate
the subwoofer’s efforts on
the ultradeep bass sounds
required by today’s films and
music. If you are using smaller
bookshelf speakers that do not
extend to the lower bass fre­quencies, set the low-pass
crossover control to a higher
setting, between 120Hz and
150Hz. This control is not used
when the LFE switch ∞ is in
the “LFE” position.

switch

which the

sounds.

If you will be away from home
for an extended period of time,
or if the subwoofer will not be

adjustment depends on sev­eral variables such as room
size, subwoofer placement,
type of main speakers and

used, switch the Master
Power switch ¢ to the “Off”
position.

position. Adjust the subwoofer
level so that the volume of the
bass information is pleasing
to you.

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