Marshall Amplification JCM 900 4100 User manual

JCM 900
4100
OWNER’S MANUAL

The JCM900 4100 was first made
in 1990 in response to the perennial
problem of ‘not enough gain’. At the
time, guitarists were hot-rodding their
Marshall amps to achieve higher levels
of gain, which was expensive and far
from reliable. And so Marshall set to
work on a remedy.
Designing an amplifier with masses of
gain is relatively straight forward. The
art is to make a high gain amplifier that
is not excessively noisy, is reliable and
retains great tone. After a period of
extended R&D, Marshall provided the
world with the answer: the JCM900
Series.
“Shredders of the world, please note:
The JCM900 saves you the trouble of
having your amp hot-rodded.”
- Guitar Player Magazine, 1991.
The British made, all-valve 4100
is not only designed to be high
gain, it is designed to be versatile,
with two independently controlled
footswitchable channels, each with its
own distinct voicing, Master Volume and
footswitchable Reverb.
Channel A is voiced for brilliant clean
tones when the Gain control is set lower.
Turn up the Gain for crunch and more
driven tones. Channel B is boosted
with enough Gain for fearsome lead
tones, ranging from classic lead on
lower settings to screaming shred on
maximum.
The 100 Watt 4100 uses four high
quality 5881 output valves for their
unique harmonic distortion properties,
as well as two ECC83 valves in the
preamp. With most valve amplifiers,
particularly Marshalls, the best sounds
are achieved when, along with the
preamp Gain cranked, the Master
Volume is set high enough to overdrive
the output valves.
It is the delicate working balance
between the preamp and the power
stage of the amplifier, and the interaction
between the EQ controls, that will
determine the sonic character produced
by the 4100 – experiment to find your
sound.
Thank you for choosing Marshall and
we sincerely hope that your JCM900
4100 Hi Gain Dual Reverb amplifier will
provide you with countless hours of ‘hot-
rodded’ tone.
INTRODUCTION
OVERVIEW
FOLLOW ALL INSTRUCTIONS AND HEED ALL WARNINGS
KEEP THESE INSTRUCTIONS
ENGLISH

WARNING:
Before going any further, make sure
that your amplifier is compatible with
your electricity supply. If you have any
doubt, please seek help from a qualified
technician – your Marshall dealer can
help you in this respect.
MAINS INPUT & FUSE:
Your amplifier is provided with a
detachable mains (power) lead which
should be connected to the Mains Input
socket on the rear panel of the amplifier.
The specific mains input voltage rating
that your amplifier has been
manufactured for is indicated on the
rear panel of the amplifier.
The correct value and type of mains
fuse is specified on the rear panel of the
amplifier.
NEVER attempt to bypass the fuse or fit
one of the incorrect value or type.
TRANSPORTING YOUR EQUIPMENT:
Please ensure that your amplifier is
switched off, unplugged from the mains
electricity supply and all removable
cables have been disconnected from
your equipment before attempting to
move it.
IMPORTANT SET UP INFORMATION:
1. Make sure that the speaker
cabinet(s) impedance matches that of
the amplifier. See IMPEDANCE
SELECT in this manual (Rear Panel
Functions #6). Always use a proper
speaker cable. Never use a screened
(shielded) guitar cable for this
purpose.
NOTE: Before connecting or
disconnecting the speaker cabinet(s)
you MUST switch the amplifier off
and disconnect it from the mains
electricity supply. Switching on
without a speaker plugged in will
damage the amplifier.
2. Ensure that the VOLUME controls on
the front panel are set to zero.
3. Connect the supplied mains (power)
lead into the MAINS INPUT on the
rear panel first and then into the
mains electricity supply. (Rear Panel
Functions #13)
4. Plug your guitar into the INPUT jack
socket on the front panel.
5. Turn the front panel POWER on
(Front Panel Functions #15) and wait
for a few minutes before going to
point 6 below,
6. After waiting, engage the STANDBY
switch (Front Panel Functions #14).
7. Turn the VOLUME controls up to
your preferred level and your amp is
ready to play.
WARNING! IMPORTANT SAFETY INSTRUCTIONS

1. INPUT
Connects the instrument to the
amplifier. (Use a high quality screened
lead).
2. CHANNEL A PREAMP GAIN
Sets the GAIN level for CHANNEL A.
Lower settings for clean sounds, higher
settings for medium drive and crunch.
3. CHANNEL B LEAD GAIN
Sets the GAIN level for the boosted
CHANNEL B. Lower settings for more
classic lead tones, higher settings for
maximum drive and sustain.
4, 5, 6, & 7. TREBLE, MIDDLE, BASS &
PRESENCE
Passive rotary EQ circuit. The
interactive controls provide a wide
range of tonal variation for both
channels.
8. CHANNEL A REVERB
Controls the amount of REVERB on
CHANNEL A.
9. CHANNEL A MASTER VOLUME
Controls the overall VOLUME level of
CHANNEL A.
10. CHANNEL B REVERB
Controls the amount of REVERB on
CHANNEL B.
11. CHANNEL B MASTER VOLUME
Controls the overall VOLUME level of
CHANNEL B.
12. CHANNEL B ‘ON’ PUSH SWITCH/LED
Indicates red when CHANNEL B is
selected either manually or by remote
footswitch.
13. FOOTSWITCH
Connects the remote dual footswitch for
Channel A/B switching and Reverb On/
Off (part # PEDL-91004).
14. STANDBY SWITCH
This switch is used in conjunction with
the mains POWER switch (item #15) to
‘warm up’ the amplifier before use and
to prolong the life of the output valves.
When powering up the amplifier always
FRONT PANEL FUNCTIONS
0
1
POWER STANDBY VOLUME REVERB
VOLUME REVERB PRESENCE BASS MIDDLE TREBLE LEAD GAIN GAIN
INPUT
FOOT
SWITCH
MASTER
(CH. B)
PUSH ON
(CH. B)
MASTER
(CH. A)
PREAMP
(CH. B)
PREAMP
(CH. A)
Model 4100
2
010
4 6
8 2
010
4 6
82
010
4
6
8 2
010
4 6
82
010
4 6
82
010
4 6
82
010
4 6
82
010
4 6
84
020
812
16 2
0
10
4 6
8
15. 14. 13. 12. 11. 10. 9.

0
1
POWER STANDBY VOLUME REVERB VOLUME
REVERB PRESENCE BASS MIDDLE TREBLE LEAD GAIN GAIN
INPUT
FOOT
SWITCH
MASTER
(CH. B)
PUSH ON
(CH. B)
MASTER
(CH. A)
PREAMP
(CH. B)
PREAMP
(CH. A)
Model 4100
2
010
4 6
8 2
010
4 6
82
01
0
4
6
8 2
010
4 6
82
010
4 6
82
010
4 6
82
010
4 6
82
010
4 6
84
020
812
16 2
0
10
4 6
8
9.
engage the mains POWER switch first
(1), leaving the STANDBY switch to the
STANDBY position (0).
This allows the application of the voltage
required to heat the valves to their
correct operating temperature. After
approximately two minutes the valves
will have reached the correct operating
temperature and the STANDBY switch
can be engaged (1).
In order to prolong valve life, the
STANDBY switch alone should be used
to turn the amplifier on and off during
breaks in performance.
15. POWER
This is the on/off switch for the mains
power to the amplifier. When it is
switched on (1), the switch will light
red. Please ensure that the amplifier is
switched off (0) and unplugged from the
mains electricity supply before being
moved.
FRONT PANEL FUNCTIONS (CONT.)
8. 7. 6. 5. 4. 3. 2. 1.

1. LOOP LEVEL
Adjusts the level of the FX Loop from
-10dBV to +4dBu. Higher settings
match modern FX processors and
lower settings match floor FX pedals.
NOTE: Some FX such as Distortion
and Compressor are best suited to
connection via the front panel INPUT
jack socket.
2. SEND
Connect to the input of an external FX.
3. RETURN
Connect to the output of an external FX.
4. RECORDING COMPENSATED LINE OUTPUT
Use this jack socket for direct
connection to recording equipment or
PA system. The signal is specially filtered
for optimum recording performance.
5. DIRECT LINE OUTPUT
Unfiltered preamp signal for connection
to an external power amplifier. NOTE:
Using the DIRECT LINE OUTPUT does
not omit the need for a speaker load
to be connected to the 4100 output
stage. See item #1 in Important Setup
Information in this manual.
6. IMPEDANCE SELECTOR
Two-way switch for matching amplifier
and speaker impedance.
7. LOUDSPEAKERS
Parallel wired jack sockets for
connecting speaker cabinet(s). Ensure
that the speaker cabinet(s) is easily
capable of handling the full amplifier
power and that the impedance is
correctly selected (item #6). If in any
doubt, consult your Marshall dealer for
advice.
8. MODE
Switches the amplifier from HIGH to
LOW power output. The LOW setting
configures the output stage to ‘triode’
operation which halves the rated output.
The HIGH power position configures the
amplifier to ‘pentode’ operation for full
100 Watt rated power output. NOTE:
Switching to lower power will not half
the volume of the amplifier. The purpose
of this feature is to alter the amplifier’s
MAINS INPUT FUSE
120V ~ 60Hz
375 Watts
EFFECTS
SEND
HIGH LOW
LOOP
LEVEL
RETURN RECORDING
COMPENSATED
DIRECT
(4)16 8
HIGH LOW
FAIL
OPV-1-4 OPV-2-3
DO NOT USE WITHOUT
CONNECTING SPEAKER LOAD
SEE MANUAL FOR CORRECT
OPERATION AND RATING
T500mA T500mA
220/240V - T2A
110/120V - T4A
FAIL
LINE OUTPUT POWER LEVEL
OUTPUT
OUTPUT
VALVE FUSE
WARNING!: SHOCK HAZARD. DO NOT OPEN.
TO REDUCE THE RISK OF FIRE OR ELECTRIC SHOCK DO NOT EXPOSE THIS EQUIPMENT TO
RAIN OR MOISTURE. THIS APPARATUS MUST BE EARTHED.
AVIS!: RISQUE DE CHOC ELECTRIQUE. NE PAS OUVRIR. POUR EVITER LES RISQUES
D’INCENDIE ET DE DECHARGES ELECTRIQUES, N’EXPOSEZ JAMAIS CET APPAREIL A L’HUMIDITE
OU A LA PLUIE. CONNECTER CET APPAREIL A LA TERRE.
CAUTION!: TO REDUCE THE RISK OF ELECTRIC SHOCK DO NOT REMOVE COVER.
NO USER SERVICEABLE PARTS INSIDE. REFER SERVICING TO QUALIFIED SERVICE PERSONNEL.
ATTENTION!: POUR EVITER LES RISQUES DE DECHARGES ELECTRIQUES, NE PAS
OUVRIR LE COUVERCLE. CET APPAREIL NE COMPORTE AUCUNE PIECE SUSCEPTIBLE D’ETRE
REPAREE PAR VOS SOINS. FAITES TOUJOURS APPEL A UN TECHNICIEN QUALIFIE POUR TOUTE
REPARATION.
OUTPUT : 100 WATTS RMS INTO 8Ω
!
Made in England by
Marshall Amplification plc,
Bletchley, Milton Keynes, England.
IMPEDANCE
SELECT
MODE
LOUDSPEAKERS
100W
R.M.S.
WARNING: DO NOT OBSTRUCT VENTILATION GRILLES
ATTENTION: NE PAS OBSTRUER LES GRILLES DE VENTILA
TION
REAR PANEL FUNCTIONS
1. 2. 3 4. 5. 6. 7.

MAINS INPUT FUSE
120V ~ 60Hz
375 Watts
EFFECTS
SEND
HIGH LOW
LOOP
LEVEL
RETURN RECORDING
COMPENSATED
DIRECT
(4)16 8
HIGH LOW
FAIL
OPV-1-4 OPV-2-3
DO NOT USE WITHOUT CONNECTING
SPEAKER LOAD
SEE MANUAL FOR CORRECT OPERA
TION AND RATING
T500mA T500mA
220/240V - T2A
110/120V - T4A
FAIL
LINE OUTPUT POWER LEVEL OUTPUT
OUTPUT
VALVE FUSE
WARNING!: SHOCK HAZARD. DO NOT OPEN.
TO REDUCE THE RISK OF FIRE OR ELECTRIC SHOCK DO NOT EXPOSE THIS EQUIPMENT TO
RAIN OR MOISTURE. THIS APPARATUS MUST BE EARTHED.
AVIS!: RISQUE DE CHOC ELECTRIQUE. NE PAS OUVRIR. POUR EVITER LES RISQUES
D’INCENDIE ET DE DECHARGES ELECTRIQUES, N’EXPOSEZ JAMAIS CET APPAREIL A L’HUMIDITE
OU A LA PLUIE. CONNECTER CET APPAREIL A LA TERRE.
CAUTION!: TO REDUCE THE RISK OF ELECTRIC SHOCK DO NOT REMOVE COVER.
NO USER SERVICEABLE PARTS INSIDE. REFER SERVICING TO QUALIFIED SERVICE PERSONNEL.
ATTENTION!: POUR EVITER LES RISQUES DE DECHARGES ELECTRIQUES, NE PAS
OUVRIR LE COUVERCLE. CET APPAREIL NE COMPORTE AUCUNE PIECE SUSCEPTIBLE D’ETRE
REPAREE PAR VOS SOINS. FAITES TOUJOURS APPEL A UN TECHNICIEN QUALIFIE POUR TOUTE
REPARATION.
OUTPUT : 100 WATTS RMS INTO 8Ω
!
Made in England by
Marshall Amplification plc,
Bletchley, Milton Keynes, England.
IMPEDANCE
SELECT
MODE
LOUDSPEAKERS
100W R.M.S.
WARNING: DO NOT OBSTRUCT VENTILATION GRILLES
ATTENTION: NE PAS OBSTRUER LES GRILLES DE VENTILA
TION
tonal character and playing feel.
9. & 10. VALVE FAILURE LED (OPV1 – 4)
VALVE FUSE (OPV1 – 4)
In the case of output valve failure
the fuse (item # 10) will operate,
illuminating the FAIL LED (item # 9).
This fuse applies to output valves 1 & 4.
The amplifier will continue to function
on reduced power – valves 2 & 3 only. In
this event service should be obtained as
soon as possible to prevent premature
aging of output valves 2 & 3.
11. & 12. VALVE FAILURE LED (OPV2 – 3)
VALVE FUSE (OPV2 – 3)
Similar functions to items #9 & #10
above, but applying to output valves 2
& 3.
13. MAINS INPUT
Connects the amplifier to the mains
power supply. NOTE: Always ensure
that the incoming mains voltage
matches that of the amplifier. If in doubt
consult your Marshall dealer.
14. MAINS POWER FUSE
Protects the amplifier and mains supply
in the event of a fault. NOTE: Always
ensure that the fuse value matches the
labelling on the amplifier rear panel. If in
doubt consult your Marshall dealer.
REAR PANEL FUNCTIONS (CONT.)
8. 10.9. 12.11. 14.13.