Luxman M-900u User manual

Owner`s Manual
LUXMAN CORPORATION, JAPAN
STEREO POWER AMPLIFIER
M-900u

Contents
Precautions ············································································································· 1
Features of This Unit································································································ 2
Names and Functions······························································································ 4
Connections ············································································································ 8
Block Diagram······································································································· 13
Specifications ········································································································ 14
Before Asking for Repair Services·········································································· 15

STEREO POWER AMPLIFIER M-900u
1
Precautions
Installation place
Install this unit in a location where good ventilation and heat
radiation is assured.
Especially, installation of this unit where direct sunlight is
present, where the temperature rises excessively high such
as close to a heater, or where it is humid or dusty may cause
a malfunction even if heat is efficiently released.
Therefore, do not install this unit in such places.
Ventilation holes
Do not block the ventilation holes of the top and bottom pan-
els. If the amplifier is installed on a rack or the like, secure
ample space for cooling and leave the door open. Do not pile
up other things on the amplifier and never put articles on it.
Failure to observe this may cause a malfunction.
Note:
For heat dispersal, do not install this equipment in a confined
space such as a book case or similar unit.
Precautions in connecting with other
components
When connecting this product to input devices such as a
control amplifier, be sure to turn off the power of this product
and all other connected devices. Failure to observe this may
generate a strong noise resulting in speaker damage or cause
a malfunction.
The pin-plug to be inserted in each input terminal of this unit
shall be pushed in firmly. If the grounding terminal is inade-
quately connected, noises including hum may be generated,
resulting in an adverse S/N ratio.
Cautions in connecting speakers
When making speaker system connections, exercise extra
care not to short-circuit between ⊕and ⊖of the speaker
terminals and speaker input terminals of this unit.
If a large signal is applied to the amplifier with its circuit left
short-circuited, a large current may be passed through the
output circuit and cause a malfunction.
The sound is not generated shortly after
the power supply is turned on.
This amplifier is equipped with a time muting circuit in order to
separate the output circuit. Therefore, no sound is generated
shortly after the power supply is turned on.
If the volume control is moved to a high sound level before
the time muting circuit is canceled, a large sound is suddenly
generated. Please be advised that the volume control of the
input device such as a control amplifier shall be set to a low
level at first and adjusted according to your taste after sound
comes out of the speakers.
Protection circuit
This product is equipped with a protection circuit that is ac-
tivated upon detection of overcurrent, abnormally high tem-
perature, and DC drift to protect the amplifier and speakers.
When the protection circuit is activated, the output to the
speaker terminal is shut off and the standby indicator lights
up to show that this product is in the standby state. If the
protection circuit is frequently activated even after the power
switch is turned off, the power plug is disconnected from the
wall outlet, the power plug is connected again after a lapse
of a certain time, and the power switch is turned on again,
please consult your dealer.
Repair and adjustment
When repair and adjustments are needed, please ask the
dealer where you bought the unit.
Cleaning
For cleaning, use a piece of soft cloth to wipe the unit such as
cleaning cloth available on the market. If the unit has become
very dirty, remove the dirt with soft cloth absorbing a small
amount of neutral detergent, and then wipe the unit with dry
cloth. Do not use a solvent like benzine or thinner because
such a substance can often damage the exterior.
* Note
Wall
**
*
Exercise extra care when this unit is unpacked, assembled,
transported, and installed because this unit is heavy.
SAFETY CAUTIONS
CAUTION

2
Features of This Unit
4 x 2 output structure
This product has inherited the idea of 4 x 4 output from
B-1000f, and has adopted the structure of 4 parallels x 2
modules, that is, 2 modules of 4-parallel push-pull amplifi-
cation circuit structured with 3-stage Darlington are used for
each channel.
Rated output of 150 W+150 W (8Ω), 300 W+300 W (4Ω)
ODNF
- Only Distortion Negative Feedback -
The amplification feedback circuit that has acquired the high-
speed primary slew rate and ultra-wide bandwidth by feeding
back only distortion components generated during amplifica-
tion to maintain the pure sound quality of the main-amplifier
that is almost non-feedback.
The newest version, 4.0, has achieved the low impedance
and high S/N ratio of the transmission circuit thanks to 4-par-
allelized first stage and Darlington-connected second stage
of the amplification circuit.
In addition, the input stages of the error detection circuit are
3-parallelized to improve distortion and noise.
BTL connection mode
The BTL connection mode with use of 2 units of this product
has achieved a high-quality and high-power monaural ampli-
fier structure.
2-channel input selector
Capability of switching between unbalanced input of RCA
terminal made of copper alloy and balanced input of XLR
terminal manufactured by Neutrik that supports high-grade
balanced signal transmission.
Balanced input phase selection
Balanced input phase selection switch equipped, which is
useful for the case of connecting foreign-made input devices.
Selector relay
Selector relay with high sound quality used in the key point of
Luxman amplifier, which enhances the separation and cross-
talk performances.
High-inertia power supply
High-inertia power supply circuit that combines a large-ca-
pacity EI-core-type power transformer using rectangular
copper winding wires with customizable 20,000μF × 4 block
capacitors.

STEREO POWER AMPLIFIER M-900u
3
4-parallel speaker relay
Impedance of speaker output lines reduced thanks to place-
ment of 4-parallel contact structure of speaker relays with low
resistance value for each channel.
Schottky barrier diode
Application of schottky barrier diode manufactured by Nihon
Inter Electronics Corporation that has less switching noises
and higher conversion efficiency to the DC voltage for the
power supply rectifier circuit.
LUXMAN’s original OFC wires
Our original OFC wires are used in the internal wiring to
achieve smooth signal transmission thanks to the spiral wrap
shielding on each core and the non-plating process on the
core wire.
Peel coat, PCB
Dielectric effect of resist eliminated by using copper foil of
100μm in thickness and gold plating on audio circuit board
instead of using resist.
High-grade analog meter
Large-sized analog meter with shower light equipped, light
OFF/meter OFF selectable.
Loopless chassis
This unit consists of the independent construction of a
loopless chassis to eliminate increased ground impedance
caused by chassis current.
Large type of speaker terminals
Speaker terminals with right and left identical characteristics
layout, which is compatible with Y lugs to enable easy con-
nection with extra-thick speaker cables.
AC inlet
This inlet enables the connection with an external power ca-
ble.
Cast-iron insulator
This unit is equipped with gradation cast-iron insulators that
cuts out unnecessary external vibration and strongly supports
the weight of this unit.

4
Names and Functions
1 . Standby indicator (STAND BY)
Indicates that this unit is in the standby state.
This indicator lights when the operation switch is turned off
after the main power switch on the rear panel is turned on.
When the operation switch is turned on and when the main
power switch is turned off, this indicator turns off.
2. Operation indicator (OPERATION)
Blinks (for approx. 15 sec.) in the time muting mode when
the operation switch is turned on and lights up when the
operation state is activated afterward.
3. Operation switch (OPERATION)
Turns this unit from the standby state to operation state.
When the main power switch on the rear panel is turned on
to set this unit to the standby state and this switch is turned
on, this unit is set to the operation state.
When wiring or connection is performed, be sure to turn off
this switch.
4. Input indicator (LINE/BAL LINE)
Indicates the input selected with the input switch.
5. Input switch (INPUT)
Selects the unbalanced input terminal (LINE) or balanced
input terminal (BAL LINE), both of which are located on the
rear panel.
Every time this switch is pressed, the selection changes as
follows: LINE→BAL LINE→LINE→BAL LINE→LINE…
Factory default: LINE
When this switch is toggled, the input/output muting circuit
is activated and no sound is generated during the time.
LINE BAL LINE
LINE
BAL LINE
6 753 421 8
Front panel

STEREO POWER AMPLIFIER M-900u
5
6. Display switch (DISPLAY)
Selects the power meter light and display.
This switch operates differently depending on the setting of
the BTL selection switch on the rear panel.
When STEREO is selected:
• Every time this switch is pressed, the setting changes
as follows: light ON/power meter ON→light OFF/power
meter ON→light OFF/power meter OFF→light ON/power
meter ON...
When BTL (MONO) is selected:
• Only the power meter at the left side operates.
• Every time this switch is pressed, the setting changes as
follows: right and left lights ON/power meter (left) ON→left
light ON/power meter (left) ON→light OFF/power meter
(left) ON→light OFF/power meter OFF→right and left
lights ON/power meter (left) ON...
Factory default: as follows
At STEREO, power meter light ON
power meter display ON
At BTL (MONO), power meter right and left lights ON
power meter display ON (left)
The setting of the display switch is memorized in both STE-
REO and BTL (MONO), respectively.
7. BTL indicator (BTL)
Lights when the BTL selection switch on the rear panel is
set to BTL (MONO) to show that this unit turns to a monau-
ral amplifier with BTL connection.
When the BTL selection switch is set to STEREO, this indi-
cator turns off to show that this unit turns to a stereo ampli-
fier with normal connection.
Factory default: No lighting (STEREO)
8. Power meters
Indicates the level of output to the speakers, with lighting
equipped.
The light/power meter operate differently depending on the
setting of the display switch and the setting of the BTL se-
lection switch on the rear panel.
• This meter indicates the output level in decibels from
−60dB through +10 dB during the power meter in op-
eration.
• When STEREO is selected, the meter at left reads the level
of the L channel, and the meter at right reads the level of
the R channel.
• When BTL (MONO) is selected, the level is indicated only
with the left meter.

6
Names and Functions
9. STEREO/BTL selection switch
(STEREO/BTL (MONO))
When STEREO is selected, this unit operates as a stereo
power amplifier.
When BTL (MONO) is selected, this unit operates as a mon-
aural power amplifier with BTL connection.
Factory default: STEREO
10. Phase inverter switch
(BAL LINE PHASE)
Change the phase when the balance input terminal is used.
The phase shall be corresponding to the phase of the input
device.
NORMAL Position① GROUND
② COLD (–)
③ HOT (+)
INVERT Position① GROUND
② HOT (+)
③ COLD (–)
11. Main power switch (MAIN POWER)
Turns this unit to the standby state.
When this switch is turned on, the standby indicator on the
front panel lights yellow to show that this unit turns to the
standby state.
When this switch is turned off, the standby indicator on the
front panel turns off to show that the main power is turned
off.
12. Signal ground (ground terminal)
(SIGNAL GROUND)
Is a ground terminal for devices to be connected to this unit.
This terminal is used to reduce noise when other devices
are connected.
This terminal is designed not for safety.
13. Unbalanced input terminal
(INPUTS LINE)
Coaxial input terminal to receive unbalanced audio signals
of a line level
Connect this terminal to an unbalanced output of an input
device such as a control amplifier with a pin-plug cable.
Audio input signals coming to LINE are selected with the
input switch on the front panel and delivered.
9 10 11 12
16
13 14
17
15
Rear panel

STEREO POWER AMPLIFIER M-900u
7
14. Balanced input terminal
(INPUTS BAL LINE)
XLR connector input terminal to receive balanced audio sig-
nals of a line level
Connect this terminal to a balanced output of an input de-
vice such as a control amplifier with a balanced cable.
Audio input signals coming to BAL LINE are selected with
the input switch on the front panel and delivered.
To enjoy sound reproduction properly, set the phase invert-
er switch in accordance with the phase of the balanced out-
put of the input device such as a control amplifier.
When BTL (MONO) is selected, only signals from the L side
are valid, and therefore, securely connect the left channel
output terminal (L side) of the input device to the L side input
terminal of M-900u for the left channel and the right channel
output terminal (R side) of the input device to the L side input
terminal of another M-900u for the right channel.
Signals from the R side input terminal are not provided.
15. AC inlet (AC IN)
Connects the accessory power cable.
The power shall be supplied from a household wall socket.
16. Speaker terminals (SPEAKERS)
Connect the left speaker to the L side speaker terminal of
this unit and the right speaker to the R side speaker terminal
in consideration of the polarity.
At this moment, securely connect the ⊕terminal of the
speaker system to the speaker terminal ⊕(red) of this unit,
and the ⊖terminal of the speaker system to the speaker
terminal ⊖(black) of this unit.
Speaker systems with impedance of 4-16 Ω can be con-
nected to this unit.
When BTL (MONO) is selected, this unit turns to a monaural
power amplifier. Therefore, either right or left speaker sys-
tem can be connected exclusively.
If stereo playback is desired, another M-900u is required.
When BTL (MONO) is selected, securely connect the ⊕ter-
minal of the speaker system to the ⊕terminal (red) (BTL⊕)
of the L side speaker terminal of this unit, and the ⊖termi-
nal of the speaker system to the ⊕terminal (red) (BTL⊖) of
the R side speaker terminal of this unit.
Speaker systems with impedance of 8-16 Ω can be con-
nected to this unit in the BTL mode.
17. Remote input terminals (REMOTE IN)
Connects a control amplifier (e.g. C-900u) equipped with
dedicated remote output terminal using a dedicated remote
cable.
If the main power switch is turned on and this unit is turned
to the standby state, this unit can be turned to the operat-
ing state or standby state in conjunction with the operation
switch of a control amplifier.
When the main power switch is turned off, this unit does not
operate in conjunction with the control amplifier.
Memory reset
The following operations restore all the settings to the fac-
tory defaults.
(1) Turn the power supply to the standby state.
(2) Perform the following operations while pressing the dis-
play switch.
(3) Turn on the operation switch.
(4) The input indicator, LINE, and BAL LINE light up in 5
seconds.
(5) Press the input switch once.
(6) The power supply turns to the standby state.
(7) Release the display switch.
That’s all for memory reset.
Factory default
Item Default
Input LINE
Display
At STEREO Power meter light ON
Power meter display ON
At BTL (MONO) Power meter right and left
lights ON
Power meter display ON (left)

8
Connections
Before Connecting
Before connecting other devices, connect the jack side of the
accessory power cable to the AC inlet of this unit.
Before connection, turn off the main power switch of this
unit and the power of all other connected devices to prevent
unexpected accidents that may be caused by noise.
How to connect power supply
Use the accessory power cable and insert the AC plug in an
outlet on the wall in the room where the unit will be installed.
How to connect the input terminals to
input devices such as a control amplifier
Connect between the output terminals of an input device
such as a control amplifier and the input terminals of this unit
with pin-plug cables or balanced cables.
At this connection, exercise extra care not to conduct wrong
connection between right and left channels. If the right and
left channels are connected reversely, the localization of
sound images is deteriorated, thus failing in normal stereo
playback.
If pin-plug cables are used, inadequate connection of the
grounding of the cables may generate noises including hum,
resulting in an adverse S/N ratio. Surely insert the connection
plug.
How to connect the remote input terminal
to a control amplifier
Connect between the remote output terminal of a control am-
plifier such as Luxman C-900u and the remote input terminal
of this unit with the dedicated remote cable supplied with this
unit.
After this connection, this unit can be turned to the operating
state in conjunction with the operation switch of the control
amplifier.
Use the dedicated remote cable only for the connection be-
tween this unit and Luxman control amplifiers.

STEREO POWER AMPLIFIER M-900u
9
How to connect speakers
[stereo connection]
Connect the left-channel speaker to the SPEAKER L terminal
of this unit and the right-channel speaker to the SPEAKER R
terminal.
Securely connect the !terminal of the speaker system to the
speaker terminal !(red) of this unit, and the @terminal of the
speaker system to the speaker terminal @(black) of this unit.
If the !and @terminals are reversely connected to either of
the right and left speaker systems, the acoustic phases of the
signals reproduced from the right and left speaker systems
are also reversed. In such a case, be aware that the sound
level in the low range will be reduced and the acoustic stability
will worsen, thus failing in normal stereo playback.
[BTL connection]
When BTL (MONO) is selected, this unit turns to a monaural
power amplifier, and if stereo playback is desired, another
M-900u is required.
Connect the left-channel speaker to the speaker terminal of
M-900u for the left channel, and the right-channel speaker to
the speaker terminal of M-900u for the right channel.
Securely connect the !terminal of the speaker system to
the red SPEAKERS L terminal (BTL !) of this unit, and the
@terminal of the speaker system to the red SPEAKERS R
terminal (BTL @) of this unit.
Use extra care not to connect in reverse polarity or reverse
right/left channel to perform normal stereo playback.
Some speaker selection switch boxes have the ⊖speaker ter-
minal connected to the common ground terminal.
When BTL (MONO) is selected, the inverted output side of this
unit is short-circuited to the common ground and excessive
current flows into this unit.
The protection circuit is activated, which may cause a break-
down. Therefore, do not use such a switch box.
When BTL (MONO) is selected, this unit shall be directly con-
nected to speaker systems, or the switch box with which the
⊖speaker terminal can be independently selected shall be
used.
When this unit is connected to an input device or a speaker
system, turn off the main power switch of this unit or turn this
unit to the standby state to protect the amplifier and speakers
from excessive input.
After connection, ensure that connections are appropriately
performed and turn this unit to the operating state.

10
Connections
通常ステレオ再生
CONTROL AMP
SPEAKER SYSTEM
L R
L R
REMOTE
CD/SACD PLAYER
CD/SACD PLAYER
LR
–
+
–
+
L LRR
Normal stereophonic reproduction

STEREO POWER AMPLIFIER M-900u
11
CONTROL AMP
CD/SACD PLAYER
CD/SACD PLAYER
L R
L R
Set to
BTL (MONO)
REMOTE
Set to
BTL (MONO)
SPEAKER SYSTEM
L R
–
+
–
+
R R
L L
BTL stereophonic reproduction

12
CONTROL AMP
CD/SACD PLAYER
CD/SACD PLAYER
L R L R
REMOTE
SPEAKER SYSTEM
–
+
–
+
–
+
–
+
R-HIGH L-HIGH
LR
Hi Hi
Low Low
R-LOW L-LOW
Connections
Bi-amplifier/stereophonic reproduction

STEREO POWER AMPLIFIER M-900u
13
Block Diagram
-B3
+B3
+B5 +B4
-B2R
+B2R
-B2L
+B2L
-B2L +B2L -B1L +B1L -B1R +B1R -B2R +B2R -B3 +B3
+B5 +B4
+B1L -B1L +B1R +B1L -B1L -B1R -B1R +B1R
LINEL
AC IN
LINER
BTL AMPLIFIER
BALANCE L
1. GND 2. COLD (-) 3. HOT (+)
12
3
BALANCE R
1. GND 2. COLD (-) 3. HOT (+)
12
3
BAL./UNBAL. AMP (NORMAL) BAL./UNBAL. AMP (INVERT) BAL./UNBAL. AMP (NORMAL) BAL./UNBAL. AMP (INVERT)
REMOTE IN OPERATION
SWITCH
INPUT SELECTOR SWITCH DISPLAY
SWITCH PHASE
INVERT BTL
SWITCH
OPERATION
INDICATOR
REG. µ COM. REG. RELAY
REG. OP. AMP.
REG. ODNF. AMP.
POWER SWITCH
AC RELAY 1
AC RELAY 2
TRANS. AMP.
TEMP.
REG. ODNF. AMP.
RECT. ODNF. RECT. ODNF. RECT. OP. RECT. PWR. RECT. PWR.
RECT. µ COM.
RECT. RELAY
TRANS. CONTROL
OUT SP-L
SPEAKER OUT
L
SPEAKER OUT
R
OUT SP-R
DC. OC. PRT.
TEMP. PRT.
DC. OC. PRT.
TEMP. PRT.
LOG./RECT. PEAK HOLD
INPUT MUTE
CONTROL CIRCUIT
METER L METER R
BAL INV R-ON
BAL NOR R-ON
BTL BAL NOR-ON
BAL INV L-ON
BTL BAL INV-ON
BAL NOR L-ON
BAL LINE-ON
LINE R-ON
LINE L-ON
AC RELAY (0.9s=t-ON)
AC RELAY D (0<t<1S-ON)
POWER TRANS. TEMP. TN
IN MUTE L
IN MUTE R
STANDBY LINE BAL BTL
Rch PROTECT IN
Lch PROTECT IN
OUT SP R
OUT SP L
METER LD R
METER LD L
METER L
L-OUT R-OUT
METER R
+12V
LOG./RECT. PEAK HOLD
INPUT MUTE

14
Specifications
Continuous rated output (stereo) 150 W + 150 W (8 Ω)
300 W + 300 W (4 Ω)
Continuous rated output (BTL) 600 W (8 Ω)
Instantaneous maximum output
(stereo)
1200 W + 1200 W (1 Ω)
Instantaneous maximum output
(BTL)
2400 W (2 Ω)
Input sensitivity 1.24 V/150 W, load 8 Ω
Gain 29 dB
Input impedance LINE 51 kΩ
BAL LINE 34 kΩ
Total harmonic distortion 0.008 % or less/1kHz · 150 W, load 8 Ω
0.1 % or less/20Hz-20 kHz
Frequency response +0, −0.1dB/20Hz-20kHz
+0, −3.0dB/1Hz-130kHz
S/N ratio 117 dB (IHF-A weighted, input short)
Damping factor 710
Attached equipment •Main power switch •Operation switch
•Input switch •BTL selection switch
•Phase inverter switch •Power meters
•Display switch •Unbalanced input terminal
•Balanced input terminal •Speaker terminal
•Signal ground terminal •Remote input terminal
•AC inlet
Accessories •Power cable •Dedicated remote cable
•Owner’s manual •Safety cautions
Power consumption 540 W
280 W (under no signal)
1.0 W (at standby)
Power supply 230 V ~ (50 Hz)
Max. external dimensions 440 (W) × 224 (H) × 485 (D)mm
Weight 48.0 kg
* Specifications and appearance are subject to change without notice.

STEREO POWER AMPLIFIER M-900u
15
Before Asking for Repair ServicesBefore Asking for Repair Services
While the unit is used, an unusual phenomenon may be confused as a malfunction for a certain reason. Prior to asking us for repair
services, please check the table below and read the instruction manual for the subsidiary devices. If the cause of the malfunction can-
not be identified, please contact your dealer.
Problem Cause Solution
No power is supplied even
though the operation switch is
pressed.
· The power plug is disconnected from the
wall outlet, or it is not completely inserted.
· Insert the power plug in the wall outlet com-
pletely.
· The power plug is disconnected from the
AC inlet, or it is not inserted completely.
· Insert the power plug in the AC inlet com-
pletely.
· The main power switch is turned off. · Turn on the main power switch.
No sound is generated. · The volume control of the input device is set
to the minimum level.
· Rotate the volume control of the input de-
vice clockwise to adjust the sound volume.
· The input switch is not set to the input signal
to be reproduced.
· Set the input switch to the input signal to be
reproduced.
· Cable connections are incomplete. · Make cable connections securely.
· The output level of the input device is set to
the minimum position.
· Adjust the output level.
No sound is generated on one
side.
· The connecting cable is not connected on
one side only.
· Make cable connections securely.
Sound is generated but the
sound volume is low.
The sound volume is low only at
one side channel.
Inappropriate localization of
sound images
No bass is generated.
· The BTL connection is made, but the STE-
REO/BTL selection switch is set to STE-
REO.
· When the BTL connection is made, set
the STEREO/BTL selection switch to BTL
(MONO).
· The stereo connection is made, but the
STEREO/BTL selection switch is set to BTL
(MONO).
· When the stereo connection is made, set
the STEREO/BTL selection switch to STE-
REO.
· The balance control of the control amplifier
is set to one side.
· Adjust the balance control of the control
amplifier according to your taste.
· The R channel and L channel are connected
reversely.
· Connect the R channel and L channel ap-
propriately.
· The ⊕and ⊖terminals of the speaker sys-
tem on one side are connected reversely.
· Connect the ⊕and ⊖terminals of the
speaker systems on both sides appropri-
ately.
Humming sound (boon or zzz
noise) is generated.
· The ground side of the pin-plug cable has
no contact with the terminal.
· Make connections securely so that the
ground side of the pin-plug cable can be
connected.
The display window does not
light up.
· The display is set to OFF. · Use the display switch to set the display to
ON.

16
MEMO

LUXMAN CORPORATION, JAPAN AG00987E21A
Printed in China